Noninvasive Instrumentation and Measurement in Medical Diagnosis
Second Edition
Robert B. Northrop
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4
7 .3 .2 Transcutaneous tcpCO2 Sensing
8 .2 Instrumental Methods
.2 .1 Introduction
8 .2 .2 Dispersive Spectrophotometry
8 .2 .6 Flame Photometry
8 .2 .7 Gas Chromatography
.2 .8 Mass Spectrometry
8 3 What Can Be Learned from Urine?
8 3 1 Introduction
8 3 2 Diagnosis of Early-Stage Pancreatic Cancer from Proteins
8 .4 What Can Be Learned from Feces?
8 .5 What Can Be Learned from Saliva?
Preface
This book is about the instruments, and sometimes the procedures, which are used for noninvasive medical diagnosis (NIMD) and therapy Why st ress “noninvasive (NI)”? NIMD is preferred whenever possible to avoid the risks and expenses attendant to surgically opening the body surface, for example, infections, adverse systemic reactions to anesthesia, dye injection, antibiotics and other medications, as well as surgical error In many instances, NIMD is less expensive than equivalent invasive procedures, in other cases (e .g ., imagi ng) it is the only practical means of diagnosis, and in some cases (e g , imagi ng) it is the most expensive diagnostic modality because of the complex technologies involved .
This text was written based both on the author’s experience in teaching EE 370, Biomedical Instrumentation I, for over 35 years in the Electrical & Computer Engineering Department (now Biomedical Engineering Department) at the University of Connecticut, and on his personal research on certain prototype, NI medical instrumentation systems The contents of EE 370 have evolved with instrumentation technology and our knowledge of human diseases, physiology, biochemistry, and cell biology
As NIMD is a rapidly growing, interdisciplinary field, a number of the systems described in this text are prototypes that are currently in the research phase of their development . In the author’s opinion, these systems will probably be effective, and given Food and Drug Administration (FDA) approval, we will eventually see their general acceptance and use by the medical community . I have seen photonics and photonic means of measurement play an increasingly important role in modern NIMD instrument design . As the reader will see, the diagnostic photon is becoming increasingly important .
This book is intended for use in an introductory classroom course on Noninvasive Medical Instrumentation and Measurements taken by juniors, seniors, and graduate students in biomedical engineering It wil l also serve as a reference book for medical students and other health professionals interested in the topic . Practicing physicians and nurses interested in learning the state of the art in this important field will also find this text valuable Physicists, biophysicists, and physiologists working in the biomedical field will also find it of interest
Reader background: Readers are assumed to have had introductory, core courses in human (medical) physiology, biomedical engineering, engineering systems analysis, and in electronic circuits Their mathematical skills should include an introductory course on differential equations, as well as college-level algebra and calculus As the result of taking these courses, the readers should be skilled in understanding systems block diagrams, simple electronic circuits, the concepts of frequency response and transfer functions, and the use of ordinary differential equations to describe systems’ dynamics It is also important to have an understanding of how the physiological parameters being measured figure in human health . Much of the material in this text is descriptive However, many systems are analyzed in detail The teacher who considers adopting this text for classroom use should be advised that there are no chapter home problems .
In writing the second edition of this text, I have been amazed at the depth, breadth, and quality of the information available on the topic of NIMD and all its modalities on the Internet I can be criticized for using and citing Internet sources because they are often ephemeral in the purest sense I estimate the half-life of a web resource as being about 5 years However, web resources are a window on cutting-edge medical technologies . Sometime, the view begins with university press releases on new medical research A good search engine, such as Google com, is invaluable Obviously, I have also relied on standard texts and referred journal references in my writing . Noninvasive Instrumentation and Measurements in Medical Diagnosis, 2nd edition, is organized into 18 chapters, and includes an Index, an extensive Bibliography, and a comprehensive Glossary Below are the summarized chapter contents:
In Chapter 1, Introduction to Noninvasive Medical Measurements, I define what is meant by NI measurements and give many examples . (Some persons might argue that use of a colonoscope or a bronchoscope is in fact an invasive procedure; however, I classify their use as minimally invasive ) Also provided is an overview and history of the use of simple, NI procedures to diagnose disease as practiced in the nineteenth century and earlier, and I explain their importance in modern medicine . Chapter 2, Visual Inspection of Tissues with Endoscopes and Other Optical Devices, describes the simple, modern, NI optical instruments that allow the medical practitioner to directly inspect tissues for foreign objects, infections, polyps, tumors, etc Attention is given to the use of ophthalmoscopes and slit lamps to inspect the retina, the cornea, and internal structures of the eye . Various types of endoscopes are described that allow direct inspection of a variety of tissues and
organs accessible from without the body (e .g ., the lungs, colon, stomach, urethra, bladder, and renal pelvis) Modern, coherent fiber-optic bundles are used in some applications with miniature, high-resolution, digital TV cameras .
Chapter 3, Noninvasive Diagnosis Using Sounds Originating from within the Body, treats the medically important sounds arising from within the body (the fetal heart, heart, lungs, joints, blood vessel bruits, and otoacoustic emissions) . Basic instrumentation is described, including the stethoscope, microphones, filters, and the use of FFT frequency analysis The growing importance of time–frequency spectrograms in the description of sounds, and in NIMD is stressed .
In Chapter 4, Measurement of Electrical Potentials and Magnetic Fields from the Body Surface, we first describe the sources of skin-surface electrical potential from electrically active internal organs (heart, brain, muscles, retina, cochlea, nerves) The signal-coupling properties of various bioelectrodes are treated, followed by sections on the medical significance of each of the potentials (ECG, EMG, EEG, ERG, EOG, ECoG) . Di fferential and medical isolation amplifiers are covered in detail, as are low-noise amplifier analysis and design The SQUID, and biomagnetic measurements with SQUID arrays are also described .
In Chapter 5, Noninvasive Measurement of Blood Pressure, the use of the sphygmomanometer is described (manual and automatic) in measuring systolic and diastolic blood pressure Blood pressure estimates can also be made from finger plethysmographs .
Chapter 6, Body Temperature Measurements, considers the basic thermometer (mercury and electronic) and its importance in detecting fever or hypothermia . Basic heat flow relations are used to describe thermometer response time The design and physics of the no-touch, LIR thermometer that reads body temperature from the eardrum is elaborated .
Chapter 7, Noninvasive Blood Gas Sensing with Electrodes, describes the use of electrochemical electrodes on heated skin used to transcutaneously measure tissue pCO2 and tissue pO2
In Chapter 8, Tests on Naturally Voided Body Fluids, we review a number of analytical instrumental techniques that can be used on body fluids (urine, saliva, and breath) to measure the concentrations of certain ions, glucose, urea, drugs, VOCs, etc . Various analytical instruments used in laboratory medicine are described, including dispersive and nondispersive spectroscopy, surface plasmon resonance, ion-selective electrodes, flame photometers, gas chromatography, and mass spectrometry . We t hen go on to review what can be found of diagnostic significance in urine, feces, saliva, and breath
Chapter 9, Plethysmography, describes the applications of plethysmography in quantifying body volume changes due to breathing, muscle contraction, blood flow, etc Body and limb volume changes can be measured by water displacement, pneumatically, or electronically .
Chapter 10, Pulmonary Function Tests, first describes the volume displacement spirometer, then the use of turbines and pneumotachs to electronically measure respiratory flow and volumes Spirometers are used to quantify mechanical respiratory functions with such parameters as lung tidal volume, forced expiratory volumes, etc Their use is critical in detecting obstructive lung diseases and plotting their progress . Also covered is the use of inhaled inert gases in the measurement of respiratory function
The Measurement of Basal Metabolism is described in Chapter 11 The physiology behind the measurement protocol is explained, and the apparatus and protocol are given . Basal metabolism measurement is a basic NI means of assessing thyroid function
Chapter 12, Ocular Tonometry, discusses the importance to monitor the intraocular pressure of healthy vision The designs of various tonometers including the no-touch air-puff applanation system are described .
Chapter 13, Noninvasive Tests Involving the Input of Audible Sound Energy, treats measurements in which low-frequency acoustic energy (generally 2–2000 Hz) is used to characterize the respiratory system, or the ear canal and eardrum . We first describe the concepts of acoustic resistance, capacitance, and inertance (inductance), and show how a complex acoustic impedance (Z) can be simply measured .
The RAIMS system devised by the author is described for the measurement of the acoustic Z of the lungs and bronchial tree Acoustic Z is also shown to be useful in characterizing the compliance of the eardrum and the tympanal reflex . Fi nally, a means of measuring the acoustic transfer function of the chest cavity and lungs with transmitted white noise is described The measurement and acoustic Z of the lungs have application in detecting and quantifying obstructive lung disease .
In Chapter 14, Noninvasive Tests Using Ultrasound (Excluding Imaging), we begin by describing the physics and mathematics associated with the Doppler effect . Next covered is the use of CW and pulsed Doppler ultrasound to measure blood velocity, and its diagnostic utility Another
application is the use of air-coupled ultrasound to measure the ocular pulse . The closed-loop, constant phase, NOTOPM system of Northrop and Nilakhe is described, and the uses of the ocular pulse in diagnosis are detailed . The same air-coupled, ultrasound ranging system was used by Northrop (1980) to design a prototype, no-touch infant apnea monitor
A significant improvement on the NOTOPM system, the constant-phase, closed-loop, type 1, ranging system (CPRS), is presented and its possible future applications in the quantitative measurement of aneurisms, heart motion, and the shape of internal organs are described (The CPRS system gives a simultaneous output of incremental distance and velocity .)
Chapter 15, Noninvasive Applications of Photon Radiation (Excluding Imaging), covers a wide spectrum of topics (pun intended): x-ray bone densitometry by the DEXA method; tissue fluorescence spectroscopy; optical interferometric measurement of nanometer tissue displacements; Laser Doppler velocimetry; percutaneous IR spectroscopy; glucose measurement in the aqueous humor of the eye by polarimetery (the rotation of linearly polarized light); pulse oximetry; and applications of Raman spectroscopy in detecting cancer and dissolved glucose are also described
Chapter 16, A Survey of Medical Imaging Systems, first considers the input modalities of coherent light, x-rays, ultrasound, and γ -rays from radioisotopes The mathematical means for tomographic imaging are described, including the Radon transform and deblurring techniques The production of x-rays and their use in flat imaging and CT scanners is treated . Also covered are magnetic resonance imaging (MRI), positron emission tomography (PET) imaging, radio-nuclide (isotope) imaging (SPECT), ultrasonic imaging, and passive, LIR thermal imaging in diagnosis . The present and future imaging capabilities of the emerging field of optical coherence tomography (OCT) are described . Also explored is the new use of coherent x-ray diffraction imaging in high-resolution mammography; all you need is a synchrotron
In Chapter 17, Innovations in Noninvasive Instrumentation and Measurements, we consider possible modalities whereby medical professionals can noninvasively examine DNA for mutations, expediting the diagnosis of cancer and research on genetically caused diseases The DNA microarray, or “gene chip” and the means of reading out probe hits on target molecules are described . We present the use of fluorescence tagging and laser scanning to read out gene chips, as well as electrical readouts Biochips are also being designed that can test for specific antibodies to bacteria and viruses, as well as the pathogen coat proteins themselves . The detection of other, non-DNA molecules found in urine and saliva that may be associated with cancer growth is described
Chapter 18, Introduction to Noninvasive Therapies, describes the therapeutic uses of externally applied electric currents, electric and magnetic fields, heat and percutaneous ultrasound energy to treat a variety of medical conditions, including but not limited to bone fractures, cancers, glioblastomas, osteoarthritis, etc Interferential current therapy (ICT) has been shown to be effective in various degrees for the relief of chronic pain (TENS), stimulation of muscles, causing increased blood flow, reducing edema, and genera stimulation of tissue healing . Many claims exist for the therapeutic effects of externally applied, pulsed magnetic fields These benefits have been observed in various clinical studies in various degrees . In Section 18 .15, we examine the exciting new field of gene editing with CRISPR-Cas and CRISPR-Cpf1 endonucleases in potential therapies for certain genetic diseases
Robert B. Northrop Chaplin, Connecticut
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About the Author
Robert B. Northrop, PhD, was born in White Plains, NY, in 1935 . After graduating from Staples High School in Westport, CT, he majored in electrical engineering at MIT, graduating with a bachelor’s degree in 1956 At the University of Connecticut, he received a master’s degree in electrical and systems engineering in 1958 . As the result of a long-standing interest in physiology, he entered a PhD program at UCONN in animal physiology, doing research on the neuromuscular physiology of molluscan catch muscles . He earned his PhD in 1964 .
In 1963, he rejoined the UCONN EE Department as a lecturer, and was hired as an assistant professor of EE in 1964 . I n collaboration with his PhD advisor, Dr . Edward G . Boettiger, he secured a 5-year training grant in 1965 from NIGMS (NIH), and started one of the first, interdisciplinary, biomedical engineering graduate training programs in New England UCONN currently awards MS and PhD degrees in this field of study, as well as BS degrees in biomedical engineering .
Throughout his career, Dr Northrop’s research interests have been broad and interdisciplinary and have been centered on biomedical engineering and physiology . He has done sponsored research (by the AFOSR) on the neurophysiology of insect and frog vision, and devised theoretical models for visual neural signal processing He also did sponsor research on electrofishing and developed, in collaboration with Northeast Utilities, effective, working systems for gu idance and control of migrating fish in hydroelectric plant waterways on the Connecticut River at Holyoke, MA, using underwater electric fields .
Still another area of his sponsored research (by NIH) has been in the design and simulation of nonlinear, adaptive, digital controllers to regulate in vivo drug concentrations or physiological parameters, such as pain, blood pressure, or blood glucose in diabetics . A n outgrowth of this research led to his development of mathematical models for the dynamics of the human immune system, which were used to investigate theoretical therapies for autoimmune diseases, cancer, and HIV infection
Biomedical instrumentation has also been an active research area for Dr . Northrop and his graduate students: An NIH grant supported studies on the use of the ocular pulse to detect obstructions in the carotid arteries Minute pulsations of the cornea from arterial circulation in the eyeball were sensed using a no-touch, phase-locked, ultrasound technique . Ocular pulse waveforms were shown to be related to cerebral blood flow in rabbits and humans
More recently, Dr . Northrop addressed the problem of noninvasive (NI) blood glucose measurement for diabetics Starting with a Phase I SBIR grant, he developed a means of estimating blood glucose by reflecting a beam of polarized light off the front surface of the lens of the eye, and measuring the very small optical rotation resulting from glucose in the aqueous humor, which in turn is proportional to blood glucose As an offshoot of techniques developed in micropolarimetry, he developed a magnetic sample chamber for glucose measurement in biotechnology applications T he water solvent was used as the Faraday optical medium
He has written numerous papers in refereed journals, and 14 textbooks: Analog Electronic Circuits (1990); Introduction to Instrumentation and Measurements (1997); Endogenous and Exogenous Regulation and Control of Physiological Systems (2000); Dynamic Modeling of Neuro-Sensory Systems (2001); Noninvasive Instrumentation and Measurements in Medical Diagnosis (2002); Signals and Systems Analysis in Biomedical Engineering (2003); Analysis and Application of Analog Electronic Circuits in Biomedical Engineering (2004); Introduction to Instrumentation and Measurements —2nd edition (2005); Introduction to Molecular Biology, Genomics & Proteomics for Biomedical Engineers (with Anne N . Connor) (2009); Signals and Systems Analysis in Biomedical Engineering—2nd edition (2010); Introduction to Complexity and Complex Systems (2011); Analysis and Application of Analog Electronic Circuits in Biomedical Engineering—2nd edition (2012); Ecological Sustainability: Understanding Complex Issues (with Anne N . Connor) (2013), Introduction to Instrumentation and Measurements —3rd edition (2014)
Dr . Northrop is a member of Sigma Xi, Phi Kappa Phi, Eta Kappa Nu, Tau Beta Pi, and a Founding Fellow, Connecticut Academy of Engineers (2003)
His current research interest lies in complex systems and sustainability
Dr . Northrop was on the Electrical & Systems Engineering faculty at UCONN until his retirement in June 1997 T hroughout this time, he was director of the Biomedical Engineering Graduate Program . As Emeritus Professor, he writes texts, sails, and travels . He lives in Chaplin, CT, with his wife and a barn cat
Acronyms and Abbreviations
Aβ Amyloid- β polypeptide
ANSI American National Standards Institute
BAc Blood alcohol
BBR Blackbody radiation
[bG] Blood glucose concentration
BPD Bronchopulmonary dysplasia
BPF Ba nd-pass filter
BTE Behind the ear (hearing aid)
C3 (in physiology) Command, communication, and control (of biochemical and physiological processes)
CAT Computer-assisted tomography; Computed axial tomography (X-ray); Computer of average transients
cfDNA Ci rculating free DNA
CMOS Complementary metal oxide semiconductor
CMRR Common-mode rejection ratio
COLD Ch ronic obstructive lung disease
CPAP Continuous positive airway pressure (ventilation)
CPDRS Constant-phase distance ranging system
Cpf1 A CR ISPR-associated endonuclease
CRISPR Acronym for Clustered regularly interspaced short palindromic repeats
CRT Cathode ray tube
CSF Cerebrospinal fluid
DA Di fferential (difference) amplifier
DARPA Defense Advanced Research Projects Agency
D-C Di rect coupled
DC Di rect current
DEI Di ffraction-enhanced imaging
DEXA Dual energy X-ray absorption
DLCO Di ffusion capacity of the lungs for carbon monoxide
DR Di ffuse reflectance
DRIS Di ffuse reflectance imaging system
dsDNA Double-stranded DNA
DSF Di rectional sensitivity function
DSP Digital signal processing
DVT Deep vein thrombosis
DXA Dual-energy, x-ray absorption (test)
EECP En hanced external counterpulsation
EM Electron micrograph, electromagnetic (fields)
EMF Electromotive force (in V)
EMG Electromyogram
ERP Event-related potential
EtG Ethyl glucuronide
FEV1 Forced Expiratory Volume in 1 s
FISH Fluorescence in situ hybridization
FVC Forced vital capacity
GBP Glycan-binding protein
GE Genetically engineered
HA Hearing aid
Hz Hertz (cycles per second)
IC Integrated circuit
ICT Interferential current therapy (also IFT)
IFC Interferential current (tissue stimulation)
[ifG] Interstitial fluid glucose concentration
IFT Interferential current therapy
INR International normalized ratio
iOS Apple’s proprietary mobile operating system (OS) for its handheld devices, such as the iPhone, iPad, and iPod Touch The OS is based on the Macintosh OSX
IPAP In spiratory positive airway pressure
IPPV Intermittent positive pressure ventilation
IR I nfrared
ISCEV International Society for Clinical Electrophysiology
ISE Ion-selective electrode
ITC In t he (ear) canal (hearing aids)
IV I ntravenous
lacZ
A gene in the lac operon T he proteins from the lac operon are lacZ, lacY, and lacA T he lac operon, found in Escherichia coli and other enteric bacteria, is required for the transport and metabolism of lactose
LDV Laser Doppler velocimetry
LF Low-frequency AC band 30–300 kHz
LIA Lock-in amplifier
LIFE Light-induced fluorescent endoscopy
LIR Long wave infrared
LN2 Liquid nitrogen
LOD Li mit of detection (minimum concentration of an analyte that can be distinguished from the blank) See below
LOR Li ne of response (in PET events)
MAST Medical antishock trousers
MEG Magnetoencephalogram
M-FISH FISH with multiple fluors
MIR Midrange infrared wavelength (e g , 1010–1095 cm 10)
mL Milliliter
MOS Metal oxide semiconductor
MS Mu ltiple sclerosis
MSIF Mu ltispectral imaging in the frequency domain
MSIS Mu ltispectral imaging in the spatial domain
mT MilliTesla
mtDNA Mitochondrial DNA
NADH (reduced) nicotinamide adenine dinucleotide
ND Neutral density
nDNA Nuclear DNA
NDS Nondispersive spectrophotometer
NDW Neutral-density wedge
NI Noninvasive
NIMD Noninvasive medical diagnosis
NIR Near-infrared light
NIT Noninvasive therapy
NOTOPM No -touch ocular pulse measurement
OCT Optical coherence tomography
OCV Open-circuit voltage
OD Right eye
ODE Ordinary differential equation
OIP Occlusive impedance phlebography
OLD Obstructive lung disease
OP Ocu lar pulse
OPD Optical path distance
OS Left eye
OT Output transducer (the “receiver” in hearing aids)
PA Power amplifier
PAT Photoacoustic tomography
PD Phase detector
PDS Pu lsed Doppler system; Power density spectrum
PEMF Pu lsed electromagnetic field
PENS Percutaneous electrical nerve stimulation
PLSR Partial least squares regression
PMF Pu lsed magnetic field
PPOF
Polarization-preserving optical fiber
pps Pu lses per second
PROP-Z
Programmable probiotics with lacZ
psi Pounds per square inch (pressure) (1 psi = 70 .3 g/cm 2)
PVDF Polyvinylidene fluoride
QPMS Quadrupole mass spectrometer
RAIMS
Respiratory acoustic impedance measurement system
RBC Red blood cell (erythrocyte)
RC Resistance-capacitance
RE Reference electrode
RF Radio frequency
RMS (or rms) Root mean square
RNAi
RNA interference
RPOX Reflectance pulse oximetry
RTD Resistance temperature detector
RV Residual volume of lungs
SAMHSA The (U S ) Substance Abuse and Mental Health Services Administration
SCC Short-circuit current
siRNA Small interfering RNA
[SG]
Salivary glucose concentration
SKY Spectral karyotyping of a nucleic acid
SLD Superluminescent diode
SMU Si ngle motor unit
SPECT Si ngle-photon emission tomography
SPL Sound pressure level
SPP Su rface plasmon polariton(s)
SPR Su rface plasmon resonance
SQUID
Superconducting quantum interference device
SRS St imulated Raman spectroscopy
ssDNA Si ngle-stranded DNA
STI Sexually transmitted infection
SUS Scanning ultrasound
tDCS Tra nsient DC (brain) stimulation
TEM Transverse electromagnetic (waves)
Tempco Temperature coefficient
THC Tetrahydrocannabinol
THz
TeraHertz (1 THz = 1012 Hz)
TIR Transcutaneous infrared
Tm
Melting (denaturing) temperature of a nucleic acid strand (Hydrogen bonds break)
TMS Transcranial magnetic stimulation
tracrRNA Tra nsactivating CRISPR RNA
TUS Therapeutic ultrasound
TV Tidal volume
US Ultrasound
VCCS Voltage-controlled current source
VLF Very low-frequency AC band (3–30 kHz)
VOC Volatile organic compound
Wb Weber: SI unit of magnetic flux . 1 W b/m 2 = 1 T flux density (B)
0XD Zero crossing detector
1 Introduction to Noninvasive Medical Measurements
1.1
DEFINITIONS OF NONINVASIVE, MINIMALLY INVASIVE, AND INVASIVE MEDICAL MEASUREMENTS
In this chapter, let us attempt to reach consensus about what we mean by noninvasive (NI) medical measurements . A ny measurement system that does not physically breach the skin, or enter the body deeply through an external orifice is truly NI T hus, the measurement of body temperature with a thermometer in the mouth, rectum, or ear canal is considered NI, as is the use of an otoscope to examine the outer surface of the eardrum Similarly, the use of the ophthalmoscope and slit lamp which shine light in the eyes to examine the retina and the cornea and lens, respectively, is considered NI procedures . T he transduction of sounds from the body surface (from the heart, breath, otoacoustic emissions, joint sounds, etc ) is t ruly NI, as is the recording of electric potentials on the skin from internal sources such as the heart (ECG), skeletal muscles (EMG), brain (EEG), etc Medical imaging techniques such as x-ray, x-ray tomography (CAT scan), ultrasound, magnetic resonance imaging (MRI), positron emission tomography (PET), etc are NI; they do involve the input of energetic radiation into the body, however, which generally carries low risk when proper energy levels and doses are observed
Much can be learned from blood samples; namely, ion concentrations, red blood cell density, white blood cell density, the concentrations of certain hormones, antibodies, cholesterol, drug concentrations, DNA type, pathogens, chemical indicators of chronic diseases, etc . T he drawing of small blood sample, say <1 cm3, from a superficial vein by a needle and syringe or a lancet is considered to be a minimally invasive procedure, requiring sterile technique
Endoscopy is a technique for visualizing tissues deep within the body yet topologically on the outer surface of the body A n example is bronchoscopy, where a bronchoscope is inserted through the mouth and larynx, into the trachea and bronchial tubes of the lungs to permit visualization of their surfaces and the surfaces inside larger alveoli A nother endoscope is the cystoscope which is inserted into the urethra to inspect the ureter, the prostate, and the inside of the bladder Many other types also exist (Section 2 .3) . As a rule, endoscopes require sterile technique, and in most cases, local or general anesthesia; I consider them to be moderately invasive instruments, and endoscopies moderately invasive procedures.
Some endoscopes are used invasively, such as laparoscopes, which are inserted into the abdomen through a small incision in the wall of the abdomen, chest, or back . T hey are used to examine the outsides of the internal organs (bladder, gall bladder, intestines, kidneys, liver, lungs, spine, spleen, uterus, etc ) for tumors, infections, damage from trauma, etc A nother invasive procedure, for example, is cardiac catheterization with a fiber optic endoscope in order to view heart valves
One can argue that there are fuzzy classification boundaries separating NI, minimally invasive, moderately invasive, and invasive diagnostic procedures A nyone who has undergone a colonoscopy or proctoscopy may be quick to argue that they are more invasive than minimally invasive diagnostic procedures, considering the preparation, medication (analgesia or anesthesia), and discomfort involved T hus, we argue that invasiveness should be assessed on a four-level (two-bit) scale, that is, levels 0–3 .
This text is about the instruments and measurement systems used in making modern, noninvasive medical diagnoses (NIMDs) . Some of the instruments and systems described are wellestablished, Food and Drug Administration (FDA)-approved systems; others are prototype systems that eventually may prove safe, medically and cost-effective It is important for the reader to know where the field of NI diagnostic instrumentation is headed, as well as its present status . Its evolution is rapid, fueled by the advances in information processing and storage, as well as in the fields including photonics, molecular biology, and medical physics .
Throughout the history of medicine, up to the end of the nineteenth century, most medical diagnoses were necessarily NI T he physician used his or her eyes to observe skin lesions, and inflammation in the nose, throat, gums, ears, and skin . Tactile senses in the physician’s hands were used to feel skin temperature, edema, swelling due to infection, lumps under the skin, etc
The physician’s ear was used to listen to breath, bowel, and heart sounds . T he odors of infection was sensed by the physician’s nose Exploratory surgery was seldom done because of the risk of shock due to pain and blood loss, and danger of infection . Today, considerable emphasis is on the use of NI diagnosis in health maintenance and emergency medicine Most of it can be carried out on an outpatient basis, and carries little risk of infection or complications which would add to the cost the patient’s health maintenance
organization (HMO) must pay . O n the other hand, certain NI instruments, such as the various medical imaging systems, are very expensive to build and maintain and their use fee is commensurately large . I ndeed, NI diagnostic procedures, including imaging systems, have been accused of driving up the cost of health maintenance and care T he effective but simple NI, level 0 instruments such as the electrocardiograph, the spirometer, and the slit lamp and their use certainly are not culprits in this respect . T he advantage of being able to see tumors in the middle of soft tissues such as the brain, lungs, liver, spleen, and breasts will continue to drive the need to improve the resolution of expensive imaging systems, and to ensure their use where indicated .
1.2 MODALITIES OF NI INSTRUMENTATION
NI medical instruments can be broadly classified between those passive systems that put no energy into the body, and those that input some form of radiation energy, for example, microwaves, visible and UV light, x-rays, γ -rays, sound and ultrasound, and measure what energy is either absorbed, reflected, or transmitted at different wavelengths or frequencies . Among the purely passive systems, we have the well-known electrical measurements based on active nerve and/ or muscle membranes . T hese include time-varying electrical potentials recorded from the skin surface from the heart (ECG), brain (EEG), muscles (EMG), ears (electrocochleogram [ECocG]), and eyes (EOG and ERG) Sounds from the body’s interior can also be recorded from the skin surface, including sounds from the heart valves, pericardium (friction rub), blood vessels (bruit), lungs, bronchial system, pleural cavity, eardrums (spontaneous otoacoustic emissions), joints, etc Body temperature can be sensed from the infrared radiation from the eardrum, or by physically measuring the temperature of the saliva and tissues under the tongue, or the temperature in the rectum by a liquid-in-glass thermometer, or a thermometer based on a thermistor or platinum resistance element (resistance temperature detector [RTD]) . Tissue oxygen and carbon dioxide partial pressures (pO2 and pCO2) can be measured transcutaneously with special chemical electrodes The only energy put in by endoscopes is white light required to visualize or photograph the tissue being inspected Blood pressure can be measured noninvasively by Korotkoff sounds emitted by the brachial artery as the pneumatic pressure in a sphygmomanometer cuff is slowly reduced, allowing blood to surge into an artery .
Just about every other physiological modality that can be measured noninvasively requires some small input of energy . A n important class of NI imaging systems uses pulsed ultrasonic energy T he energy level of the input ultrasound is made low enough to avoid tissue-destroying cavitation or heating . Other NI, nonimaging, diagnostic systems that use continuous-wave (CW) ultrasound include Doppler blood velocity probes and Doppler probes used to sense the fetal heartbeat or detect aneurisms
Electromagnetic radiation includes radio-frequency electromagnetic waves, THz waves, infrared (IR), visible, and ultraviolet, as well as x-rays and gamma rays (Figure 1 1) The photons from UV radiation, x-, and gamma rays have sufficient photon energy (hν) to knock atomic electrons out of their inner orbits and rupture certain molecular bonds, causing DNA mutations, etc ; UVB, x-, and gamma rays are called ionizing radiations because of the potential destruction they can cause to biomolecules as the result of ionization of water and other molecules . T hus, the use of NI instruments that emit ionizing radiation is not without some small health risk UVB photons do not penetrate the skin deeply; hence, UV damage to skin can include reddening (burns) and the initiation of various types of skin cancers T he corneas and lenses of eyes given excessive UVB radiation can develop cataracts . X- and gamma ray photons, on the other hand, can penetrate the body deeply, causing cell damage in the organs A h igh-energy x-ray photon can directly damage a DNA molecule, leading to a cellular mutation if not internally repaired by the cell If a photondislodged electron strikes a water molecule, it can create a free radical. The estimated lifetime of a free radical is ∼10 µ s, which means it can drift and encounter a DNA molecule, producing indirect damage as stable molecular configurations are restored . Note that we are mostly concerned with electromagnetic ionizing radiations in this text Certain radioisotopes used in medical imaging and in cancer therapy emit energetic alpha particles (He nuclei), beta particles (electrons), or neutrons . These energetic particles can also generate free radicals and cause DNA damage, and initiate cell death by apoptosis
X-ray machines of all sorts, bone densitometers, and CAT and PET scanners thus carry a small risk of inducing cancer, including leukemia, in the patient However, most healthy persons absorb far more ionizing radiation in the form of 5 .5 MeV alpha particles from the radioactive breakdown of inhaled, naturally occurring, radon gas (e g , 222Rn) than they do from x-rays Note that
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usually there is a long slender beak; the legs are elongate, frequently hairy; the tarsi bear long pulvilli and a small empodium. The Empidae are an extensive family of flies, with predaceous habits, the rostrum being used by the female as an instrument for impaling and sucking other flies. They are occasionally very numerous in individuals, especially in wooded districts. There is great variety; there are nearly 200 species in Britain. The forms placed in the subfamily Hybotinae are curious slender little Insects, with very convex thorax and large hind legs. In Hemerodromia the front legs are raptorial, the femora being armed with spines on which the tibiae close so as to form a sort of trap. Many Empidae execute aërial dances, and some of the species of the genus Hilara are notorious for carrying veils or nets in the form of silken webs more or less densely woven. This subject is comparatively new, the fact having been discovered by Baron Osten Sacken in 1877,[414] and it is not at all clear what purpose these peculiar constructions serve; it appears probable that they are carried by means of the hind legs, and only by the males. Mik thinks that in H. sartor the veil acts as a sort of parachute, and is of use in carrying on the aërial performance, or enhancing its effect; while in the case of other species, H. maura and H. interstincta, the object appears to be the capture or retention of prey, after the manner of spiders. The source of the silk is not known, and in fact all the details are insufficiently ascertained. The larvae of Empidae are described as cylindrical maggots, with very small head, and imperfect ventral feet; the stigmata are amphipneustic, the thoracic pair being, however, excessively small; beneath the posterior pair there is nearly always a tooth- or spinelike prominence present.
Fig. 235 A, Larva, B, pupa of Medeterus ambiguus. France. (After Perris.)
Fam. 27. Dolichopidae.—Graceful flies of metallic colours, of moderate or small size, and long legs; usually with bristles on the thorax and legs, the halteres exposed, squamae being quite absent; antennae of two short stout joints (of which the second is really two, its division being more or less distinct), with a thread-like or hair-like appendage. Proboscis short, fleshy. Claws, pulvilli, and empodium small; wings with a simple system of nervures, those on the posterior part of the wing are but few, there is no anterior basal cross-vein between the discal and second basal cells, which therefore form but one cell. This is also a very extensive family of flies, of which we have probably about 200 species in Britain. They are conspicuous on account of their golden, or golden-green colours, only a few being yellow or black. The males are remarkable for the curious special characters they possess on the feet, antennae, face, or wings. These characters are not alike in any two species; they are believed to be of the nature of ornaments, and according to Professor Aldrich and others are used as such in courtship.[415] This family of flies approaches very closely to some of the Acalyptrate Muscidae in its characters. It is united by Brauer with Empidae to form the tribe Orthogenya. Although the species are so numerous and abundant in Europe, little is known as to their metamorphoses. Some of the larvae frequent trees, living under the bark or in the overflowing sap, and are believed to be carnivorous; they are amphipneustic; a cocoon is formed, and the pupa is remarkable on account of the existence of two long horns, bearing the spiracles, on the back of the thorax; the seven pairs of abdominal spiracles being excessively minute.[416]
Fig 236 Wing of Trineura aterrima, one of the Phoridae Britain
Series 3. Cyclorrhapha Aschiza
Fam. 28. Phoridae. Small flies, with very convex thorax, small head, very small two-jointed antennae, bearing a long seta; femora more or less broad; wings with two dark, thick, approximate veins, meeting on the front margin near its middle, and besides these, three or four very fine veins, that run to the margins in a sub-parallel manner without forming any cells or forks. This obscure family of flies is of small extent, but its members are extremely common in Europe and North America, where they often occur in numbers running on the windows of houses. It is one of the most isolated groups of Diptera, and great difference of opinion prevails as to its classification. The wing-nervuration is peculiar (but varies somewhat in the species), the total absence of any cross-veins even on the basal part of the wing being remarkable. There are bristles on the head and thorax, but they are not arranged in a regular manner. The larvae live in a great variety of animal and vegetable decaying matter, and attack living Insects, and even snails, though probably only when these are in a sickly or diseased condition. The metamorphoses of several species have been described.[417] The larvae are rather slender, but sub-conical in form, with eleven segments and a very small head, amphipneustic, the body behind terminated by some pointed processes. The pupa is remarkable; it is contained in a case formed by the contracted and hardened skin of the larva; though it differs much in form from the larva the segmentation is distinct, and from the fourth segment there project two slender processes. These are breathing organs, attached to the prothorax of the imprisoned pupa; in what manner they effect a passage through the hardened larval skin is by no means clear. Perris supposes that holes for them pre-exist in the larval skin, and that the newly-formed pupa by restless movements succeeds in bringing the processes into such a position that they can pass
through the holes. The dehiscence of the puparium seems to occur in a somewhat irregular manner, as in Microdon; it is never Cyclorrhaphous, and according to Perris is occasionally Orthorrhaphous; probably there is no ptilinum.
Fig. 237 Aenigmatias blattoides. × 27. Denmark. (After Meinert.)
The Insect recently described by Meinert as Aenigmatias blattoides, [418] is so anomalous, and so little is known about it, that it cannot at present be classified. It is completely apterous; the arrangement of the body-segments is unlike that of Diptera, but the antennae and mouth-parts are said to be like those of Phoridae. The Insect was found near Copenhagen under a stone in the runs of Formica fusca. Meinert thinks it possible that the discovery of the male may prove Aenigmatias to be really allied to Phoridae, and Mik suggests that it may be the same as Platyphora lubbocki, Verrall, known to be parasitic on ants. Dahl recently described a wingless Dipteron, found living as a parasite on land-snails in the Bismarck archipelago, under the name of Puliciphora lucifera, and Wandolleck has recently made for this and some allies the new family Stethopathidae. It seems doubtful whether these forms are more than wingless Phoridae.
Fam. 29. Platypezidae.—Small flies, with porrect three-jointed antennae, first two joints short, third longer, with a terminal seta; no bristles on the back; hind legs of male, or of both sexes, with peculiar, broad, flat tarsi; the middle tibiae bear spurs; there is no empodium. Platypezidae is a small family of flies, the classification of which has always been a matter of considerable difficulty, and is still uncertain. The larvae are broad and flat, fringed at the margin with twenty-six spines; they live between the lamellae of Agaric fungi. At pupation the form alters but little; the imago emerges by a horizontal
cleft occurring at the margins of segments two and four.[419] We have four genera (Opetia, Platycnema, Platypeza, Callomyia), and nearly a score of species of Platypezidae in our British list, but very little seems to be known about them. There is much difference in the eyes of the sexes, in some at any rate of the species, they being large and contiguous in the male, but widely separated in the female.
Fig 238 Head of Pipunculus sp A, Seen from in front; B, side view, showing an antenna magnified Pyrenees
Fam. 30. Pipunculidae.[420] Small flies, with very short antennae bearing a long seta that is not terminal; head almost globular, formed, except at the back, almost entirely by the large conjoined eyes; the head is only slightly smaller in the female, but in the male the eyes are more approximate at the top. This is another of the small families of flies, that seems distinct from any other, though possessing no very important characters. In many of the flies that have very large eyes, the head is either flattened (i.e. compressed from before backwards, as in Tabanidae, Asilidae), or forced beneath the humped thorax (as in Acroceridae), but neither of these conditions exists in Pipunculus; in them the head extends far forwards, so that the area of the eye compared with the size of the body is perhaps greater than in any other Diptera. The general form is somewhat that of Anthrax, but the venation on the hind part of the wing is much less complex. There is a remarkable difference between the facets on the front and the back of these great eyes. We have three genera and about a dozen species of Pipunculidae in Britain but apparently they are far from common Insects. What is known about the life-history is almost confined to an imperfect observation by Boheman, who found the larva of P. fuscipes living after the manner of a Hymenopterous parasite in the body of a small Homopterous Insect.[421] The pupa seems to be of the type of that of Syrphidae.
Fam. 31. Conopidae. Elegant flies of moderate size, of varied colours, with abdomen slender at the base, at the tip strongly incurved and thicker; antennae inserted close together on a prominence, three-jointed, first joint sometimes very short. The upper surface of the body without bristles or with but few. There is a slender, elongate proboscis, which is retractile and usually invisible. This rather small family of flies includes some of the most remarkable forms of Diptera; it includes two divisions, the Conopinae with long antennae terminated by a very minute pointed process, and Myopinae with shorter antennae bearing a hair that is not placed at the end of the third joint. The former are the more wasp-like and elegant; the Myopinae being much more like ordinary flies, though they frequently have curious, inflated heads, with a white face. The mode of life of the larva of Conops is peculiar, it being parasitic in the interior of Bombus, or other Hymenoptera. They have been found to attack Bombus, Chalicodoma, Osmia, Vespa, Pompilus, and other Aculeates. Williston says that Orthoptera are also attacked. Conops has been seen to follow Bumble-bees and alight on them, and Williston says this act is accompanied by oviposition, the larva that is hatched boring its way into the body of the bee. Others have supposed that the flies enter the bees' nests and place their eggs in the larvae or pupae; but this is uncertain, for Conops has never been reared from a bee-larva or pupa, though it has frequently been procured from the imago: cases indeed having been recorded in which Conops has emerged from the body of a Bombus several months after the latter had been killed and placed in an entomologist's collection. The larva is broad, and when full grown apparently occupies nearly all the space of the interior of the abdomen of the bee; it has very peculiar terminal stigmata. The pupa is formed in the larval skin, which is greatly shortened and indurated for the purpose; this instar bears, in addition to the posterior stigmata, a pair of slightly projecting, anterior stigmata. We have several species of Conopidae in Britain; those belonging to the division Conopinae are all rare Insects, but the Myopinae are not so scarce; these latter are believed to be of similar habits with the Conopinae, though remarkably little is known about them. This is another of the numerous families, the relations of which are still a
subject for elucidation. Brauer places the Conopidae in his section Schizophora away from Syrphidae, but we do not comprehend on what grounds; an inspection of the head shows that there is no frontal lunule as there is in Eumyiidae; both Myopa and Conops agreeing fairly well with Syrphus as to this. We therefore place the family in its old position near Syrphus till the relations with Acalypterate Muscidae shall be better established.
Fam. 32. Syrphidae (Hover-flies).—Of moderate or rather large size, frequently spotted or banded with yellow, with a thick fleshy proboscis capable of being withdrawn into a cleft on the under side of the head; antennae not placed in definite cavities, three-jointed (usually very short), and leaving a seta that is not terminal in position, and may be feathered. Squama variable, never entirely covering the halteres; the chief (third to fifth) longitudinal veins of the wings connected near their termination by cross-veins and usually thus forming a sort of short margin parallel with the hind edge of the wing; a more or less imperfect false nervure running between the third and fourth longitudinal nervures; no empodium and generally no distinct system of bristles on the back of the body. The Syrphidae (Fig. 212) form one of the largest and best known of all the families of flies; they abound in our gardens where, in sunny weather, some species may be nearly always seen hovering over flowers, or beneath trees in places where the rays of the sun penetrate amidst the shade. There are two or three thousand species known, so that of course much variety exists; some are densely covered with hair (certain Volucella and others), many are of elegant form, and some bear a considerable resemblance to Hymenoptera of various groups. The peculiar veining of the wings permits of their easy identification, the line of two nervules, approximately parallel with the margin of the distal part of the wing (Fig. 212, D), and followed by a deep bay, being eminently characteristic, though there are some exceptions; there are a few forms in which the antennae are exceptional in having a terminal pointed process. The proboscis, besides the membranous and fleshy lips, consists of a series of pointed slender lancets, the use of which it is difficult to comprehend, as the Insects are not known to pierce either animals or vegetables, their food
being chiefly pollen; honey is also doubtless taken by some species, but the lancet-like organs appear equally ill-adapted for dealing with it. The larvae are singularly diversified; first, there are the eaters of Aphidae, or green-fly; some of these may be generally found on our rose-bushes or on thistles, when they are much covered with Aphids; they are soft, maggot-like creatures with a great capacity for changing their shape and with much power of movement, especially of the anterior part of the body, which is stretched out and moved about to obtain and spear their prey: some of them are very transparent, so that the movements of the internal organs and their vivid colours can readily be seen: like so many other carnivorous Insects, their voracity appears to be insatiable. The larvae of many of the ordinary Hover-flies are of this kind. Eristalis and its allies are totally different, they live in water saturated with filth, or with decaying vegetable matter (the writer has found many hundreds of the larvae of Myiatropa florea in a pool of water standing in a hollow beech-tree). These rat-tailed maggots are of great interest, but as they have been described in almost every work on entomology, and as Professor Miall[422] has recently given an excellent account of their peculiarities, we need not now discuss them. Some of the flies of the genus Eristalis are very like honey-bees, and appear in old times to have been confounded with them; indeed, Osten Sacken thinks this resemblance gave rise to the "Bugonia myth," a fable of very ancient origin to the effect that Honey-bees could be procured from filth, or even putrefying carcases, by the aid of certain proceedings that savoured slightly of witchcraft, and may therefore have increased the belief of the operator in the possibility of a favourable result. It was certainly not bees that were produced from the carcases, but Osten Sacken suggests that Eristalis-flies may have been bred therein.
In the genus Volucella we meet with a third kind of Syrphid larva. These larvae are pallid, broad and fleshy, surrounded by numerous angular, somewhat spinose, outgrowths of the body; and have behind a pair of combined stigmata, in the neighbourhood of which the outgrowths are somewhat larger; these larvae live in the nests of Bees and Wasps, in which they are abundant. Some of the
Volucella, like many other Syrphidae, bear a considerable resemblance to Bees or Wasps, and this has given rise to a modern fable about them that appears to have no more legitimate basis of fact than the ancient Bees-born-of-carcases myth. It was formerly assumed that the Volucella-larvae lived on the larvae of the Bees, and that the parent flies were providentially endowed with a bee-like appearance that they might obtain entrance into the Bees' nests without being detected, and then carry out their nefarious intention of laying eggs that would hatch into larvae and subsequently destroy the larvae of the Bees. Some hard-hearted critic remarked that it was easy to understand that providence should display so great a solicitude for the welfare of the Volucella, but that it was difficult to comprehend how it could be, at the same time, so totally indifferent to the welfare of the Bees. More recently the tale has been revived and cited as an instance of the value of deceptive resemblance resulting from the action of natural selection, without reference to providence. There are, however, no facts to support any theory on the subject. Very little indeed is actually known as to the habits of Volucella in either the larval or imaginal instars; but the little that is known tends to the view that the presence of the Volucella in the nests is advantageous to both Fly and Bee. Nicolas has seen Volucella zonaria enter the nest of a Wasp; it settled at a little distance and walked in without any fuss being made. Erné has watched the Volucella-larvae in the nests, and he thinks that they eat the waste or dejections of the larvae. The writer kept under observation Volucella-larvae and portions of the cells of Bombus, containing some larvae and pupae of the Bees and some honey, but the fly-larvae did not during some weeks touch any of the Bees or honey, and ultimately died, presumably of starvation. Subsequently, he experimented with Volucella-larvae and a portion of the comb of wasps containing pupae, and again found that the flies did not attack the Hymenoptera; but on breaking a pupa of the Wasp in two, the flylarvae attacked it immediately and eagerly; so that the evidence goes to show that the Volucella-larvae act as scavengers in the nests of the Hymenoptera. Künckel d'Herculais has published an elaborate work on the European Volucella; it is remarkable for the beauty of the plates illustrating the structure, anatomy and
development, but throws little direct light on the natural history of the Insects. V. bombylans, one of the most abundant of our British species, appears in two forms, each of which has a considerable resemblance to a Bombus, and it has been supposed that each of the two forms is specially connected with the Bee it resembles, but there is no evidence to support this idea; indeed, there is some little evidence to the contrary. The genus Merodon has larvae somewhat similar to those of Volucella, but they live in bulbs of Narcissus; M. equestris has been the cause of much loss to the growers of Dutch bulbs; this Fly is interesting on account of its great variation in colour; it has been described as a whole series of distinct species.
The most remarkable of the numerous forms of Syrphid larvae are those of the genus Microdon (Fig. 239), which live in ants' nests. They have no resemblance to Insect-larvae, and when first discovered were not only supposed to be little Molluscs, but were actually described as such under the generic names of Parmula and Scutelligera. There is no appearance of segmentation of the body; the upper surface is covered by a sort of network formed by curved setae, which help to retain a coating of dirt; there is no trace externally of any head, but on the under surface there is a minute fold in which such mouth-organs as may be present are probably concealed; the sides of the body project so as to form a complex fringing arrangement; the terminal stigmata are very distinct, the lateral processes connected with them (the "Knospen" of Dr. Meijere), are, however, very irregular and placed at some distance from the stigmatic scar. Pupation occurs by the induration of the external covering and the growth from it, or rather through it, of two short horns in front. Inside this skin there is formed a soft pupa, of the kind usual in Cyclorrhaphous flies; the dehiscence of the external covering is, however, of unusual nature, three little pieces being separated from the anterior part of the upper surface, while the lower face remains intact. The account of the pupation given by Elditt[423] is not complete: the two horns that project are, it would appear, not portions of the larval skin, but belong to the head of the pupa, and according to Elditt are used to effect the dehiscence of the case for the escape of the fly; there does not appear to be any head-vesicle.
Nothing is known as to the details of the life of these anomalous larvae. M. Poujade has described two species found in France in the nests of the ant Lasius niger. [424] The larva we figure was found by Colonel Yerbury in nests of an Atta in Portugal, and an almost identical larva was recently found by Mr. Budgett in Paraguay. The flies themselves are scarce, Microdon mutabilis (formerly called M. apiformis) being one of the rarest of British flies. They have the antennae longer than is usual in Syrphidae, and the cross-veins at the outside of the wing are irregularly placed, so that the contour is very irregular: the resemblance to bees is very marked, and in some of the South American forms the hind legs are flattened and hairy like those of bees. The oviposition of Microdon has been observed by Verhoeff;[425] he noticed that the fly was frequently driven away by the ants—in this case, Formica sanguinea—but returned undiscouraged to its task.
Fig. 239 Larva of Microdon sp. Portugal. A, Dorsal view of the larva, × 4; 1, the stigmatic structure; B, posterior view of stigmatic structure; C, a portion of the marginal fringe of the body.
A brief résumé of the diverse modes of life of Syrphid larvae has been given by Perris,[426] and he also gives some information as to the curious horns of the pupae, but this latter point much wants elucidation. Whether the Syrphidae, or some of them, possess a ptilinum that helps them to emerge from the pupa is more than doubtful, though its existence has been affirmed by several authors of good repute.[427]
Fig. 240. Diopsis apicalis. Natal. A, The fly; B, extremity of cephalic protuberance, more magnified. a, The eye; b, the antenna; C, middle of head, front view; c, ocelli.
Series 4. Cyclorrhapha Schizophora
Fam. 33. Muscidae acalyptratae.—This group of flies has been the least studied of all the Diptera; it is generally treated as composed of twenty or thirty different families distinguished by very slight characters. It is, however, generally admitted by systematists that these assemblages have not the value of the families of the other divisions of Diptera, and some even go so far as to say that they are altogether only equivalent to a single family. We do not therefore think it necessary to define each one seriatim; we shall merely mention their names, and allude to certain points of interest connected with them. Taken collectively they may be defined as very small flies, with three-jointed antennae (frequently looking as if only two-jointed), bearing a bristle that is not terminally placed; frequently either destitute of squamae or having these imperfectly developed so as not to cover the halteres; and possessing a comparatively simple system of nervuration, the chief nervures being nearly straight, so that consequently few cells are formed. These characters will distinguish the group from all the other Diptera except from forms of Aschiza, and from certain Anthomyiidae, with both of which the Acalyptratae are really intimately connected. Considerable difference of opinion prevails as to the number of these divisions, but the families usually recognised are:—
1. Doryceridae.
2. Tetanoceridae.
3. Sciomyzidae.
4. Diopsidae.
5. Celyphidae.
6. Sepsidae incl. Piophilidae.
7. Chloropidae (= Oscinidae).
8. Ulidiidae.
9. Platystomidae.
10. Ephydridae.
11. Helomyzidae.
12. Dryomyzidae.
13. Borboridae.
14. Phycodromidae.
15. Thyreophoridae.
16. Scatophagidae. (= Scatomyzidae).
17. Geomyzidae incl. Opomyzidae.
18. Drosophilidae; incl. Asteidae.
19. Psilidae.
20. Tanypezidae (= Micropezidae).
21. Trypetidae.
22. Sapromyzidae incl. Lonchaeidae.
23. Rhopalomeridae.
24. Ortalidae.
25. Agromyzidae incl. Phytomyzidae.
26. Milichiidae.
27. Octhiphilidae.
28. Heteroneuridae.
29. Cordyluridae.
Brauer associates Conopidae with Acalyptrate Muscids, and calls the Group Holometopa; applying the term Schizometopa to the Calyptrate Muscidae.
No generalisation can yet be made as to the larvae of these divisions, neither can any characters be pointed out by which they can be distinguished from the larvae of the following families. In their
habits they have nothing specially distinctive, and may be said to resemble the Anthomyiidae, vegetable matter being more used as food than animal; many of them mine in the leaves or stems of plants; in the genus Dorycera the larva is aquatic, mining in the leaves of water-plants, and in Ephydridae several kinds of aquatic larvae are found, some of which are said to resemble the rat-tailed larvae of Syrphidae; certain of these larvae occur in prodigious quantities in lakes, and the Insects in some of their early stages serve the Mexicans as food, the eggs being called Ahuatle, the larvae Pusci, the pupae Koo-chah-bee. Some of the larvae of the Sciomyzidae are also aquatic: that of Tetanocera ferruginea is said by Dufour to consist only of eight segments, and to be metapneustic; Brauer considers the Acalyptrate larvae to be, however, in general, amphipneustic, like those of Calyptratae. The Chloropidae are a very important family owing to their occasional excessive multiplication, and to their living on cereals and other grasses, various parts of which they attack, sometimes causing great losses to the agriculturist. The species of the genus Chlorops are famous for the curious habit of entering human habitations in great swarms: frequently many millions being found in a single apartment. Instances of this habit have been recorded both in France and England, Cambridge being perhaps the place where the phenomenon is most persistently exhibited. In the year 1831 an enormous swarm of C. lineata was found in the Provost's Lodge at King's College and was recorded by Leonard Jenyns; in 1870 another swarm occurred in the same house if not in the same room. [428] Of late years such swarms have occurred in certain apartments in the Museums (which are not far from King's College), and always in the same apartments. No clue whatever can be obtained as to their origin; and the manner in which these flies are guided to a small area in numbers that must be seen to be believed, is most mysterious. These swarms always occur in the autumn, and it has been suggested that the individuals are seeking winter quarters.
Fig. 241 Celyphus (Paracelyphus) sp. West Africa. A, The fly seen from above; a, scutellum; b, base of wing: B, profile, with tip of abdomen bent downwards; a, scutellum; b, b, wing; c, part of abdomen.
Several members of the Acalyptratae have small wings or are wingless, as in some of our species of Borborus. The Diopsidae— none of which are European—have the sides of the head produced into long horns, at the extremity of which are placed the eyes and antennae; these curiosities (Fig. 240) are apparently common in both Hindostan and Africa. In the horned flies of the genus Elaphomyia, parts of the head are prolonged into horns of very diverse forms according to the species, but bearing on the whole a great resemblance to miniature stag-horns. A genus (Giraffomyia) with a long neck, and with partially segmented appendages, instead of horns on the head, has been recently discovered by Dr. Arthur Willey in New Britain. Equally remarkable are the species of Celyphus; they do not look like flies at all, owing to the scutellum being inflated and enlarged so as to cover all the posterior parts of the body as in the Scutellerid Hemiptera: the wings are entirely concealed, and the abdomen is reduced to a plate, with its orifice beneath, not terminal; the surface of the body is highly polished and destitute of bristles. Whether this is a mimetic form, occurring in association with similarlooking Bugs is not known. The North American genus Toxotrypana is furnished with a long ovipositor; and in this and in the shape of the body resembles the parasitic Hymenoptera. This genus was placed by Gerstaecker in Ortalidae, but is considered by later writers to be a member of the Trypetidae. This latter family is of considerable extent, and is remarkable amongst the Diptera for the way in which
the wings of many of its members are ornamented by an elaborate system of spots or marks, varying according to the species.
Fam. 34. Anthomyiidae. Flies similar in appearance to the Housefly; the main vein posterior to the middle of the wing (4th longitudinal) continued straight to the margin, not turned upwards. Eyes of the male frequently large and contiguous, bristle of antenna either feathery or bare. This very large family of flies is one of the most difficult and unattractive of the Order. Many of its members come close to the Acalyptrate Muscidae from which they are distinguished by the fact that a well-developed squama covers the halteres; others come quite as close to the Tachinidae, Muscidae and Sarcophagidae, but may readily be separated by the simple, not angulate, main vein of the wing. The larval habits are varied. Many attack vegetables, produce disintegration in them, thus facilitating decomposition. Anthomyia brassicae is renowned amongst market gardeners on account of its destructive habits. A. cana, on the contrary, is beneficial by destroying the migratory Locust Schistocerca peregrina; and in North America, A. angustifrons performs a similar office with Caloptenus spretus. One or two species have been found living in birds; in one case on the head of a species of Spermophila, in another case on a tumour of the wing of a Woodpecker. Hylemyia strigosa, a dung-frequenting species, has the peculiar habit of producing living larvae, one at a time; these larvae are so large that it would be supposed they are full grown, but this is not the case, they are really only in the first stage, an unusual amount of growth being accomplished in this stadium. Spilogaster angelicae, on the other hand, according to Portschinsky, lays a small number of very large eggs, and the resulting larvae pass from the first to the third stage of development, omitting the second stage that is usual in Eumyiid Muscidae.[429]
Fig. 242 Ugimyia sericariae. A, The perfect fly, × 3⁄2; B, tracheal chamber of a silkworm, with body of a larva of Ugimyia projecting; a, front part of the maggot; b, stigmatic orifice of the maggot; c, stigma of the silkworm (After Sasaki )
Fam. 35. Tachinidae. First posterior cell of wing nearly or quite closed. Squamae large, covering the halteres: antennal arista bare: upper surface of body usually bristly. This is an enormous family of flies, the larvae of which live parasitically in other living Insects, Lepidopterous larvae being especially haunted. Many have been reared from the Insects in which they live, but beyond this little is known of the life-histories, and still less of the structure of the larvae of the Tachinidae, although these Insects are of the very first importance in the economy of Nature. The eggs are usually deposited by the parent-flies near or on the head of the victim; Riley supposed that the fly buzzes about the victim and deposits an egg with rapidity, but a circumstantial account given by Weeks[430] discloses a very different process: the fly he watched sat on a leaf quietly facing a caterpillar of Datana engaged in feeding at a distance of rather less than a quarter of an inch. "Seizing a moment when the head of the larva was likely to remain stationary, the fly stealthily and rapidly bent her abdomen downward and extended from the last segment what proved to be an ovipositor. This passed forward beneath her body and between the legs until it projected beyond and nearly on a level with the head of the fly and came in contact with the eye of the larva upon which an egg was deposited," making an addition to five already there. Ugimyia sericariae does great harm in Japan by attacking the silkworm, and in the case of this fly the eggs are believed to be introduced into the victim by being laid on mulberry leaves and swallowed with the food; several observers agree as to the eggs being laid on the leaves, but the fact that they are swallowed by the silkworm is not so certain. Sasaki has given an extremely interesting account of the development of this larva.[431] According to him, the young larva, after hatching in the alimentary canal, bores through it, and enters a nerve-ganglion, feeding there for about a week, after which the necessity for air becoming greater, as usual with larvae, the maggot leaves the
nervous system and enters the tracheal system, boring into a tube near a stigmatic orifice of the silkworm, where it forms a chamber for itself by biting portions of the tissues and fastening them together with saliva. In this it completes its growth, feeding on the interior of the silkworm with its anterior part, and breathing through the stigmatic orifice of its host; after this it makes its exit and buries itself deeply in the ground, where it pupates. The work of rupturing the puparium by the use of the ptilinum is fully described by Sasaki, and also the fact that the fly mounts to the surface of the earth by the aid of this same peculiar air-bladder, which is alternately contracted and distended. Five, or more, of the Ugimyia-maggots may be found in one caterpillar, but only one of them reaches maturity, and emerges from the body. The Tachinid flies appear to waste a large proportion of their eggs by injudicious oviposition; but they make up for this by the wide circle of their victims, for a single species has been known to infest Insects of two or three different Orders.
Fig. 243 Diagrammatic section of silkworm to show the habits of Ugimyia. a, Young larva; b, egg of Ugimyia in stomach of the silkworm; c, larva in a nerve-ganglion; d, larva entering a ganglion; e, larva embedded in tracheal chamber, as shown in Fig. 242, B. (After Sasaki.)
The species of Miltogramma—of which there are many in Europe and two in England—live at the expense of Fossorial Hymenoptera by a curious sort of indirect parasitism. They are obscure little flies, somewhat resembling the common House-fly, but they are adepts on the wing and have the art of ovipositing with extreme rapidity; they follow a Hymenopteron as it is carrying the prey to the nest for its young. When the wasp alights on the ground at the entrance to the nest, the Miltogramma swoops down and rapidly deposits one or more eggs on the prey the wasp designs as food for its own young. Afterwards the larvae of the fly eat up the food, and in consequence of the greater rapidity of their growth, the young of the
Hymenopteron perishes. Some of them are said to deposit living larvae, not eggs. Fabre has drawn a very interesting picture of the relations that exist between a species of Miltogramma and a Fossorial Wasp of the genus Bembex[432] . We may remind the reader that this Hymenopteron has not the art of stinging its victims so as to keep them alive, and that it accordingly feeds its young by returning to the nest at proper intervals with a fresh supply of food, instead of provisioning the nest once and for all and then closing it. This Hymenopteron has a habit of catching the largest and most active flies—especially Tabanidae—for the benefit of its young, and it would therefore be supposed that it would be safe from the parasitism of a small and feeble fly. On the contrary, the Miltogramma adapts its tactics to the special case, and is in fact aided in doing so by the wasp itself. As if knowing that the wasp will return to the carefully-closed nest, the Miltogramma waits near it, and quietly selects the favourable moment, when the wasp is turning round to enter the nest backwards, and deposits eggs on the prey. It appears from Fabre's account that the Bembex is well aware of the presence of the fly, and would seem to entertain a great dread of it, as if conscious that it is a formidable enemy; nevertheless the wasp never attacks the little fly, but allows it sooner or later to accomplish its purpose, and will, it appears, even continue to feed the fly-larvae, though they are the certain destroyers of its own young, thus repeating the relations between cuckoo and sparrow. Most of us think the wasp stupid, and find its relations to the fly incredible or contemptible. Fabre takes a contrary view, and looks on it as a superior Uncle Toby. We sympathise with the charming French naturalist, without forming an opinion.
Doubtless there are many other interesting features to be found in the life-histories of Tachinidae, for in numbers they are legion. It is probable that we may have 200 species in Britain, and in other parts of the world they are even more abundant, about 1000 species being known in North America.[433] The family Actiidae is at present somewhat doubtful. According to Karsch,[434] it is a sub-family of Tachinidae; but the fourth longitudinal vein, it appears, is straight.
Fam. 36. Dexiidae. These Insects are distinguished from Tachinidae by the bristle of the antennae being pubescent, and the legs usually longer. The larvae, so far as known, are found in various Insects, especially in Coleoptera, and have also been found in snails. There are eleven British genera, and about a score of species.
Fam. 37. Sarcophagidae. Distinguished from Muscidae and Tachinidae by little more than that the bristle of the antennae is feathery at the base but hair-like and very fine at the tip.— Sarcophaga carnaria is one of the commonest British Insects; it is like the Blow-fly, though rather longer, conspicuously grey and black, with the thorax distinctly striped, and the pulvilli very conspicuous in the live fly. Cynomyia mortuorum is a bright blue fly rather larger than the Blow-fly, of which it is a competitor; but in this country an unsuccessful one. The larvae of the two Insects are found together, and are said to be quite indistinguishable. Cynomyia is said to lay only about half the number of eggs that the Blow-fly does, but it appears earlier in the year, and to this is attributed the fact that it is not altogether crowded out of existence by the more prolific Calliphora. The species of Sarcophagidae are usually viviparous, and one of them, Sarcophila magnifica (wohlfahrti), has the habit of occasionally depositing its progeny in the nostrils of mammals, and even of human beings, causing horrible sufferings and occasionally death: it is said to be not uncommon in Europe but does not occur in Britain. The genus Sarcophaga is numerous in species, and many of them are beneficial. Sir Sidney Saunders found in the Troad that Locusts were destroyed by the larvae of a Sarcophaga living in their bodies; and Künckel has recently observed that in Algeria several species of this genus attack Locusts and destroy large quantities by depositing living larvae in the Orthoptera. In North America the Army-worm is decimated by species of Sarcophaga.
Many of these Insects, when food is scarce, eat their own species with eagerness, and it seems probable that this habit is beneficial to the species. The parent-fly in such cases usually deposits more eggs
