FOR OFFICIAL USE ONLY 
AVIATION MEDICINE 
PRACTICE 
TITLE II—MILITARY-MEDICAL OPERATIONS COURSES 
PREPARED BY 
BUREAU OF MEDICINE AND SURGERY 
BUREAU OF NAVAL PERSONNEL 
h'AVPERS 10839 
MARCH 1949 FOR OFFICIAL USE ONLY 
AVIATION MEDICINE 
PRACTICE 
TITLE II—MILITARY-MEDICAL OPERATIONS COURSES 
PREPARED BY 
BUREAU OF MEDICINE AND SURGERY 
BUREAU OF NAVAL PERSONNEL 
MARCH 1949 
NAVPERS 10839 PREFACE 
This text is designed to acquaint medical officers who have had no 
previous training in aviation medicine with the problems that arise in 
that field. 
These problems are numerous and complex, and a detailed discussion 
of all of them has not been attempted. For the most part they are con- 
cerned with the physiology and psychology of flight, and with dynamics, 
pharmacology, and pathology. 
The human being, in his natural evolution, became adapted to the 
environmental conditions found upon the surface of the earth. However, 
now he has been called upon to work in a different environment, without 
benefit of evolution. Aviation medicine works hand in hand with aviation 
engineering to compensate for his many deficiencies in this new environ- 
ment. A better understanding of human physiology at high altitudes and 
high speeds has led to the development of mechanical devices, etc., which 
make pilots efficient and comfortable while flying in this new air age. 
This book has been prepared by the Aviation Medicine Division of 
the Bureau of Medicine and Surgery and the School of Aviation Medicine 
and Research, Naval Air Station, Pensacola, Florida, with the coopera- 
tion of the Naval Reserve Training Publications Project of the Bureau of 
Naval Personnel. 
Note.—Explanation of superior figures used throughout this book will be found 
in the bibliography at the end of each chapter. CONTENTS 
Chapter 1.—The Beginnings of Aviation Medicine 1 
Chapter 2.—The Problem of Reduced Barometric Pressures. ... 7 
Chapter 3.—The Problem of Acceleration 35 
Chapter 4.—Ophthalmology in Aviation Medicine 49 
Chapter 5.—Otolaryngology in Aviation Medicine 87 
Chapter 6.—The Cardiovascular System in Aviation Medicine, . 116 
Chapter 7.—Aviation Psychology 125 
Chapter 8.—The Psychology of Adjustment 142 
Chapter 9.—Neuropsychiatry in Relation to Aviation Medicine. . 160 
Chapter 10.—Aviation Physical Standards and the General 
Physical Examination 189 
Chapter 11.—Aviation Dentistry 205 
Chapter 12.—Operational Problems in Aviation Medicine 208 CHAPTER 1 
THE BEGINNINGS OF AVIATION MEDICINE * 
When the Wrights launched their contrap- 
tion of sticks, wire, and fabric for a 12-second 
flight on a gray December day in 1903, they 
started something—something nearly as far- 
reaching in its ultimate effect on the social 
order as the sputtering little engine with which 
James Watt ushered in the Industrial Revo- 
lution of the Eighteenth Century. The public 
took but casual interest in what was going on 
at Kitty Hawk. There is nothing to indicate 
that anyone in the medical profession took any 
more interest in it than the rest. Yet there 
was to be “an indissoluble linking of medical 
science and the art of flying,”1 as we shall see. 
While people in this country were still think- 
ing of the flying machine as a sporting proposi- 
tion, useful only in giving the daredevil a new 
way of breaking his neck, the Europeans began 
to see possibilities in it, military possibilities. 
No one envisioned aircraft capable of carrying 
sufficient payloads to be commercially worth- 
while; but the thing might serve a purpose in 
obtaining that crucial component of any mili- 
tary operation—information. Spies, scouts, pa- 
trols—these were slow, laborious, uncertain 
ways of getting information about what the 
enemy was up to. If this new machine could 
give a man a chance for a quick look from 
above, and get him back, that would be dis- 
tinctly worthwhile. Then there was the matter 
of artillery fire. Some long range guns were 
being developed, and it was difficult to make 
sure the shells were falling in the right place. 
Here again, a quick look at the right moment 
would be worth a lot. 
The Germans appear to have been the first 
to take these matters seriously enough to do 
much about it. And they were also the first 
to recognize that flying—unnatural human en- 
deavor that it is—would require some help from 
the medical department. Armstrong reports 
that as early as 1910 the Germans had formu- 
lated minimum physical standards for aviators, 
and by 1915 had a medical service for aviators2. 
Meanwhile, World War I had come along. The 
Allies still had much to learn about the use 
of aircraft and about aviation medicine. Much 
of it they learned the hard way. 
There was a great spirit of camaraderie 
among those early airmen. It is said that 
enemy aviators gave each other the grand hail- 
ing sign when they happened to pass close 
aboard, as they went about their business of 
scouting each others’ lines. Presumably the 
ground troops objected to this scouting with 
such gunfire as they could bring to bear, but 
that was all perfectly legitimate—a chance one 
had to take—and had nothing to do with the 
good fellowship among flying men. 
No one seems to know who started it—prob- 
ably each side blamed the other—but it is said 
that one day somebody carried aloft a pistol and 
took a pot shot at a friendly enemy in the air.f 
He didn’t know it, but he changed things al- 
most as much as had the Wrights. He demon- 
strated that the airplane could be used as a 
striking weapon. 
There followed the whole trend of develop- 
ment aimed at giving the man operating this 
new weapon an advantage over his adversary. 
Speed, maneuverability, range, fire power, rate 
of climb, ceiling; all these things became mat- 
ters of rapid competitive development. With 
these developments came a host of problems 
that had to be solved by the medical officer; 
problems of accelerative forces, anoxia, fatigue, 
* Prepared by Captain Wilbur E. Kellum, MC, USN 
t The writer has not been able to document this. It came to 
him from some of those pioneer aviators who were there. Per- 
haps the first offensive act was dropping a bomb or two. The 
significance is the same but it’s not quite such a good story. 
1 AVIATION MEDICINE PRACTICE 
Figure 1-1.—F9F Panther. 
psychological stress, and others. These prob- 
lems developed swiftly—there was no time for 
leisurely investigation. It will be instructive 
to examine the British experience. 
James L. Birley, a pioneer in aviation medi- 
cine, had this to say in 1920: “Up to this time 
(two years after the beginning of the war) 
officers were still being accepted as pilots and 
observers on the flimsiest medical examination 
or even on none at all, while those who were 
systematically examined were adjudged on 
standards which were originally laid down 
from the point of view of the ability of the 
candidate to march and to shoot from his 
right shoulder. It happened, accordingly, that 
a prospective candidate might be accepted with 
a blind left eye, or rejected because of flat feet. 
This anomaly was corrected by the institution 
of a central board for the examination of all 
candidates for the flying services.”3 
Dr. Birley went on to indicate that a field 
organization was necessary. Suitable medical 
officers were obtained for duty with the squad- 
rons with a view to learning about the duties 
expected of fliers and the conditions under 
which they were performed, to acquiring de- 
tailed personal knowledge of the fliers, and to 
gaining their confidence. A number of beds 
were reserved in a convenient hospital for the 
study of flying personnel whose disability ap- 
peared to be directly related to their peculiar 
work. In the last 16 months of the war nearly 
2,000 flying officers passed through this unit. 
Of these, 40 percent were deemed to be suffer- 
ing from “the fatigue inseparable from active 
service (flying in the combat zone).”* The 
intelligent interest of commanding officers was 
stimulated by encouraging them to visit this 
unit. Birley states that many of them became 
extraordinarily astute psychological observers. 
Lieutenant Colonel E. G. Seibert, one of the 
American pioneers in the field of aviation medi- 
cine, stated in 1919: 
“The experience gained by the British and 
French service was accomplished at the ex- 
pense of many wrecked lives and smashed aero- 
planes. The onrush of the German hordes in 
1914 gave no time for investigation. Every man 
of England, France, and Belgium was called 
upon to give his last ounce of energy to the 
service. At the end of the first year of the 
war the result of the stress was shown in the 
appalling individual inefficiency developed by 
the Royal Flying Corps. Sixty-five percent of 
the total strength of the corps was unfit for 
duty. Because of demands of other services, 
replacements were difficult to make. 
A remedy was sought, and attention was at- 
* The term "operational fatigue” had not been discovered, 
that convenient category was to be a development of World 
War II. 
2 Chapter I. —THE BEGINNINGS OF AVIATION MEDICINE 
tracted to medical efforts to conserve the effi- 
ciency of flying men. Concentrated effort was 
made during the following year to bring about 
changes in the care of these men and apply 
certain principles believed to be needful be- 
cause of changed conditions. The end of this 
year showed the inefficiency of the corps re- 
duced from 65 to 20 percent, and in the third 
year of the war, a further reduction to 12 per- 
cent.”* 
It would be incorrect to imply that this im- 
provement was due entirely to better care of 
the flier. We know that methods of selecting 
candidates for training were being improved 
and, certainly, commanding officers were learn- 
ing how better to conserve the usefulness of 
their flying officers. It is fair to say that the 
medical men who were pioneering the field of 
aviation medicine had much to do with all of 
this. 
When the United States entered the war 
there was a considerable body of experience 
to guide the development of medical services in 
the Army and Navy. During the winter of 
1917-1918 Major T. C. Lyster and Major Isaac 
H. Jones visited the allied forces in England, 
France, and Italy.5 Their experiences and 
observations are reported at length in the vol- 
ume titled Air Service Medical published by the 
Government Printing Office early in 1916.6 In 
a recent personal communication to the writer 
Dr. Jones states, “They were making pilots 
out of tired soldiers. Also, they used them 
until they didn’t come back. Hence we created 
the flight surgeon, for the need was obvious 
(more obvious, naturally, to us visitors than to 
those right in the midst of it).” 
Meanwhile a “medical research board” had 
been appointed to study all conditions which 
affected the efficiency of military pilots, and 
to consider all matters pertaining to their phy- 
sical and mental fitness. The board immedi- 
ately, January, 1918, established the Air Serv- 
ice Medical Research Laboratory. In May 
1919, a section of this laboratory was estab- 
lished as the “School for Flight Surgeons”. 
Through a series of changes, during which the 
Air Service Medical Research Laboratory was 
abandoned (1920), this school has survived as 
the present Air Force School of Aviation Medi- 
cine at Randolph Air Base, San Antonio, Texas. 
The discussion thus far has indicated how 
the idea of a special medical service for mili- 
tary aviation evolved from an imperative need. 
Figure 1-2.—F2H. 
3 AVIATION MEDICINE PRACTICE 
The creation of the flight surgeon has been 
reported, and it has been indicated that his 
work was early concerned with both the selec- 
tion of candidates for flight training and the 
care of the flier. Inherent in the situation which 
brought forth the new specialty of aviation 
medicine is a new philosophy of the function 
of the military officer. 
Up to this period the medical officer had been 
primarily concerned with the treatment of the 
sick and wounded and with the protection of 
the physical health of the military unit. “The 
experienced soldier, not without reason, con- 
sidered his credentials for knowing ‘what his 
men could stand’ at least as good as those of 
his medical colleague. He argued to himself 
that a doctor was in his element when he had 
someone ill to attend to, and consequently out 
of it when dealing with fit men. This criticism 
had a great deal of truth behind it. We were, to 
put it frankly, ill equipped to answer the co- 
nundrums with which we were confronted.”3 
From this point onward the problem of the 
specialist in aviation medicine was to learn 
as much as possible about the work of the avia- 
tor, to study the psychological, physical, and 
physiological stresses involved in military fly- 
ing, to find ways of selecting for training those 
who could best endure these stresses, and means 
of conserving the efficiency of those who had 
been trained. To understand these matters and, 
equally important, to command the confidence 
of the flier, it was early recognized that the 
medical officer must participate as fully as pos- 
sible in all types of flying. Out of this partici- 
pation has developed a close mutual under- 
standing and community of effort which is 
unique in the history of relationships between 
the medical and the military professions. 
The flight surgeon became a member of the 
team. He did not confine his interests to the 
clinical care of those who came to the dispen- 
sary for it. To be sure, he was there for sick 
call but his interests and activities ranged far 
beyond that. He was interested in flying. He 
actively participated in the operations of his 
outfit. He worked, flew, played, lived with his 
fliers. He knew each of them better than did 
the commanding officer, knew the commanding 
officer better than did any of them. Usually he 
had the respect and confidence of all. 
He knew the conditions under which the 
pilots flew. He concerned himself with their 
problems, which ranged from small personal or 
family situations to ways of improving oxygen 
equipment, what to do about blackout (the 
Navy was pioneering dive bombing then), and 
eventually to such larger problems as cockpit 
design and instrumentation. At the same time 
he knew the problems and troubles of the com- 
manding officer, the operational plans and 
schedules, the personnel problems. His field 
of interest was broad. It encompassed some- 
thing of several medical specialties, reached 
across certain of the basic sciences. Ophthal- 
mology, cardiology, otolaryngology, psychiatry, 
general medicine; these were instruments of 
daily use. Physiology, psychology, physics, aer- 
ology—these, among others, were areas in 
which he was at home. The flight surgeon’s 
job had many facets, endless opportunity. 
The story of aviation medicine during the 
ten years after World War I can be told briefly. 
Public interest in armaments, in all things mili- 
tary, dropped off sharply. The war to end all 
wars had been won; no one knew the peace was 
to be lost. Aviation suffered as seriously as 
the rest. It had a future in commerce, but at 
first this was not recognized; that depended 
upon further improvements of design and per- 
formance, and money was not available for the 
necessary research. Progress in aviation was 
slow during this decade. Aviation medicine 
kept pace with it. The decade is marked by only 
a few highlights which should be remembered. 
Figure 1-3.—EK-J9. 
4 Chapter I. —THE BEGINNINGS OF AVIATION MEDICINE 
By 1926 the gradual increase in civilian fly- 
ing reached a point where the need of some 
control was necessary. Airplanes, even then, 
were no respecters of state boundaries. Con- 
trol, to be effective, must be federal. The 
Bureau of Air Commerce was formed in the 
Department of Commerce. It was to pass 
through a series of changes to become the Civil 
Aeronautics Administration of the present, but 
included a medical section from the beginning. 
Dr. D. A. Myers, an Army flight surgeon, had 
begun his studies on the physiology of instru- 
ment flying, which was to constitute one of the 
outstanding contributions to the technical ad- 
vancement of aviation. Then, in 1927, Charles 
A. Lindbergh made his historic flight, and sud- 
denly the whole country was air-minded. In 
the same year Pan-American Airways started 
its far-flung development. 
By 1929 there were enough physicians asso- 
ciated with aviation, civil and military, to estab- 
lish the Aero Medical Association. A year later 
this organization started publishing the Jour- 
nal of Aviation Medicine. A glance at the litera- 
ture of aviation medicine indicates that the few 
items which appeared in this decade were the 
results of observations or studies made during 
World War I, Two important trends of develop- 
ment started during this period. Following the 
lead of Longacre at the Army School for Flight 
Surgeons, flight surgeons in the Army Air 
Corps and in the Navy began to experiment 
with the study of personality as a means of im- 
proving selection of prospective aviators. Mash- 
burn, at the same school, developed a reaction- 
time apparatus. The former trend led to in- 
tensive studies in the field of pencil and paper 
psychological tests for selecting candidates for 
training. Mashburn’s invention was followed 
by developments in the field of psychomotor 
tests (apparatus tests) for the same purpose. 
Both types of tests were to be used by the Army 
and Navy during World War II, with enormous 
savings of time, effort, and cost. 
Aviation medicine appears to have received 
its first official recognition in the Navy in 1921, 
when five medical officers were ordered to the 
Army School for Flight Surgeons. One of these, 
Lieutenant Victor S. Armstrong, was ordered 
to the Naval Medical School at Washington to 
organize courses in aviation medicine. However, 
the Navy continued to send most of its pros- 
pective flight surgeons to the Army School until 
1938. After completing the course of formal in- 
struction at the Army School these medical offi- 
cers were usually sent to Pensacola for a period 
of flight training and indoctrination. 
The decade before World War II saw swift 
developments in the field of aviation medicine. 
To recount them adequately is beyond the scope 
of this book. It will be possible to indicate 
only the more significant. 
General Armstrong has tersely outlined the 
developments in aviation to which aviation 
medicine made a large contribution: “From 
1930 on, the developmental work of the military 
services, and the demand for larger, faster 
commercial planes, resulted in an increase in 
size, weight, speed, and maneuverability of air- 
craft to a remarkable degree. By 1939 aircraft 
engines were developing three times the horse- 
power that they had had only a few years 
previously. Operating speeds had changed from 
100 to 200 miles per hour and military aircraft 
were attaining speeds in excess of 375 miles 
per hour. Commercial airlines were carrying 
thousands of tons of mail, freight, and express, 
and their passenger lists had passed the million 
mark in 1937 ”2 
It now became evident that consideration of 
the human element in further developments of 
aircraft performance would require a lot of 
study. Planes were being built that were too 
much for the human being to handle. Cock- 
pits were becoming too complex. Ceilings of 
operational altitude were such that better oxy- 
gen supplies and better protection from cold 
were essential. Accelerative forces were of 
such magnitude that thorough study was im- 
perative. The problems of adapting man to his 
newest machine and of adapting the machine 
to man were legion. Research laboratories were 
required. 
The first of these to be established in this 
new era was the Army Aero Medical Research 
Laboratory at Wright Field, Dayton, Ohio 
(1934). This laboratory has a splendid record 
of achievement. In 1939 the Navy established 
the Naval School of Aviation Medicine and Re- 
search Center at Pensacola, Florida. Two years 
later the Army Air Forces activated a research 
5 AVIATION MEDICINE PRACTICE 
section at its School of Aviation Medicine at 
Randolph Field, Texas. 
for the Navy at the Naval Air Station, Pensa- 
cola, Florida, in close cooperation with the 
Training Command and the Naval School of 
Aviation Medicine. 
Much of the results of all this will appear in 
subsequent chapters, as will a good deal of what 
was learned by research during the Second 
World War. Most of the work done after the 
beginning of that war was classified and is only 
now being made public. It is generally appre- 
ciated that aviation medicine saw vast develop- 
ments in that period, but the history of the 
period has not been written: we are too close 
to it. 
Note:—Appreciation is expressed for the assistance 
of Dr. Dean Brimhall, Director of Research of the 
Civil Aeronautics Administration, for making avail- 
able some of the original sources referred to in this 
chapter. 
BIBLIOGRAPHY 
1. Wilmer, W. H. Aviation Medicine in the A.E.F. 
Washington, Government Printing Office, 1920, 
2. Armstrong, H. G. Principles and Practices of 
Aviation Medicine. Baltimore, Williams and Wilkins, 
1943, Second Edition. 
3. Birley, J. L. The Principles of Medical Science 
as Applied to Military Aviation. A lecture delivered 
before the Royal College of Physicians. Lancet, 29 
May 1920. 
4. Seibert, E. G. Medical Studies in Aviation. 
Washington Medical Annals. 18:46-49, 1919. 
5. Jones, I. H. Flying Vistas. Philadelphia, Lippin- 
cott, 1937. 
6. Air Service Medical. Washington, Government 
Printing Office, 1919. 
Concurrently with these developments in the 
Army and Navy there evolved an increasing in- 
terest in civilian institutions. In 1938 the Mayo 
Clinic at Rochester, Minnesota, arranged to 
conduct annual physical examinations for pilots 
of some of the airlines. This activity developed 
into extensive researches, which culminated in 
the construction of a special research labora- 
tory in 1942. In Germany, all medical students 
were receiving training in aviation medicine 
by 1938. In 1939 George Washington Univer- 
sity established a graduate course in aviation 
medicine and the University of Cincinnati of- 
fered courses in the subject to undergraduate 
medical students. 
With the advent of World War II an increas- 
ing number of medical schools began teaching 
in the field of aviation medicine, and many 
civilian medical research laboratories turned 
their attention and efforts to the study of prob- 
lems in this field. Two committees of the Na- 
tional Research Council played important roles 
during this period: the committee on aviation 
medicine exerted considerable influence by 
stimulating research in civilian laboratories. 
The committee on selection and training of 
aircraft pilots actively directed an enormous 
amount of research in the fields delineated by 
its title. Some of this work was done at various 
universities but a good deal of it was done 
6 CHAPTER 2 
THE PROBLEM OF 
REDUCED BAROMETRIC PRESSURES* 
The physiological effects of reduced baromet- 
ric pressure, and the methods and means by 
which flying personnel are provided with a 
normal or near normal environment at high 
altitude, are briefly discussed in this chapter 
under the following subject headings: 
1. The physics of the atmosphere. 
2. Anoxia. 
3. The expansion of body gases at altitude. 
a. Intestinal tract, middle ear, and para- 
nasal sinuses. 
b. Aeroembolism. 
4. Oxygen equipment in aviation. 
5. Temperature variants in aviation as a 
problem. 
6. Noxious gases in aviation. 
7. Pressurized equipment and explosive de- 
compression. 
THE PHYSICS OF THE ATMOSPHERE 
No adequate understanding of the function 
of the human body can be made without an 
understanding of its environment. This is par- 
ticularly true in regard to an adequate under- 
standing of the bodily reactions in flight. 
The lower regions of the envelope of gases 
surrounding the earth make up the environ- 
ment of all mankind; however, there is a spe- 
cial state of this environment for those who 
fly in the upper reaches of the atmosphere. It 
is for this reason that we shall discuss the .at- 
mosphere of the earth with respect to the 
physics of the air in relation to human physi- 
ology. We shall concern ourselves with atmos- 
pheric composition, pressures, temperature, and 
density at sea level and at various altitudes. 
The earth is surrounded by an envelope of 
a mixture of gases and water vapor, which is 
held close to it by the force of gravity. The 
depth of the mixture of the gases is quite vari- 
able, but it is generally considered to be, 
roughly, 100 miles. This layer of gases con- 
tains about 78 percent of nitrogen and 21 per- 
cent of oxygen, and the remaining one percent 
contains traces of carbon dioxide, hydrogen, 
helium, neon, argon, krypton, and xenon. We 
are primarily concerned with three components 
of the air exclusive of water vapor, namely, 
oxygen, nitrogen, and carbon dioxide. Each is 
important for a different reason. As you well 
know, oxygen is essential for the combustion 
of body fuels (foodstuffs) and the release of 
body energy. Nitrogen has no particular value 
for living processes, but is important because, 
as an inert gas comprising almost 80 percent 
of the atmosphere, it figures prominently in 
aeroembolism. The role of carbon dioxide is 
well known to you. It is insignificant in per- 
centage of the atmosphere, but comprises about 
5 percent of the expired breath. A definite 
amount of carbon dioxide is necessary in the 
blood for control of breathing and heart ac- 
tion, but too great a concentration in an air 
sample is incompatible with life. 
The composition of the atmosphere has been 
evaluated by the collection of air samples by 
various means, including pilot balloons and 
high altitude aircraft flights, at altitudes rang- 
ing from sea level to 50 miles above. More re- 
cently the use of rocket missies for investigat- 
ing the upper atmosphere has given us more 
extensive information. The lower portion of 
the atmosphere, being more easily analyzed, 
displays a constant percentage composition of 
* Prepared by Cdr C. F. Cell, (MC). USN 
7 AVIATION MEDICINE PRACTICE 
gases. Water vapor of the atmosphere varies 
in the cloud areas, but averages about 1.2 per- 
cent. The percentage of water vapor gradually 
decreases until the air above 35,000 feet is 
practically dry. This is evidenced by the lack 
of clouds in the stratosphere. 
Briefly, we recall that there is a relationship 
between the volume, temperature, pressure, and 
density of a gas. To examine the atmosphere 
in respect to its pressure, temperature, density, 
and so on, it is important to review the Gas 
Laws, which are the physical laws to which 
gases conform in their behavior. Since air is 
a mixture of gases, its behavior will conform 
to the gas laws. Take a gas-filled cylinder with 
a tight-fitting piston; the greater the pressure 
exerted on the piston, the smaller the volume— 
and if heat is applied the gas will expand and 
occupy a greater volume. Of course, when pres- 
sure is reduced the volume is increased, and 
when the piston is cooled the volume is de- 
creased. 
In more technical language, we state the gas 
laws as follows: 
1. When the temperature remains constant, 
volume of a gas varies inversely as the pres- 
sure; that is, the greater the pressure the 
smaller the volume and, conversely, the less the 
pressure the greater the volume (PV-P‘V* (1) ) 
is the form in which this law is stated by the 
physicist. 
2. When the pressure remains constant, the 
volume of a gas varies directly as the tempera- 
ture ; that is, the warmer the larger the volume, 
or conversely, the colder the smaller the volume. 
(Physicists combine these as the gas law: 
PV = P'V'. 
T T 
3. Since the atmosphere is a mixture of 
gases (02N2C02NeKr, etc.), another gas law, 
Dalton’s Law, is relevant. It is the law of partial 
pressures, and states: The pressure of a mix- 
ture of gases in a given space is equal to the 
sum of the pressures which each gas of a mix- 
ture would exert by itself if confined in that 
same space. In other words, each gas in a 
mixture of gases exerts a pressure proportional 
to the percentage of the whole which it occu- 
pies. 
4. Another characteristic of gases which is 
important, especially in understanding the 
physics of the air in regard to physiology, is 
density. Density of a gas is the weight of a 
standard unit of volume of gas, and can be 
visualized as the number of particles (mole- 
cules) per unit volume. The greater the density 
the greater the number of molecules per unit 
of volume. The density of air (dry) is 1.293 
kg. per cu. meter. (A kilogram is equal to 2.2 
pounds; a meter is roughly a yard.) This 
measurement must be made under standard 
conditions, 15° C. and 760 mm. of mercury 
pressure. 
Bearing in mind the gas laws, and the fact 
that air is a mixture of gases, we will examine 
the atmosphere. Since air has density (weight) 
it exerts a pressure. In order to measure this 
pressure we employ a barometer. 
A simple barometer is made by filling a glass 
tube, which is sealed at one end, with mer- 
cury, and then inverting the tube in an open 
dish of mercury, so that the open end of the 
tube is below the surface of the mercury in the 
dish. The column of mercury in the tube will 
fall to a height dependent upon the air pres- 
sure. At sea level (standard conditions) the 
column will be 29.92 inches, or 760 mm. high. 
In other words, the atmospheric pressure is 
great enough to support a column of mercury 
760 mm. high. As a matter of fact, the weight 
of a column of air 1 inch square, from sea 
level to the uppermost reaches of the atmos- 
phere, is about 15 (14.7) pounds. The weight 
of 14.7 pounds per square inch is designated 
as one atmosphere. 
Let us return to our mercury barometer 
(there are other types, too) and start studying 
atmospheric pressure. If we begin a trip start- 
ing at sea level and climb up to a mountain 
peak, we notice that after we have climbed up 
1.000 ft. the column of mercury has dropped 
(gradually) from 760 mm. to 732.9 mm. At 
5.000 ft. above sea level the column is only 
632.3 mm. At 10,000 ft. the barometric pres- 
sure has dropped to 522.6 mm. We see clearly 
that as the altitude increases the atmospheric 
pressure decreases. 
This relationship has a significant and strik- 
ing aspect; namely, at 18,000 ft. the pressure 
has been reduced to 380 mm. (1/2 atmos- 
phere) ; at 34,000 ft., to 190 mm. (1/4 atmos- 
phere), and at 42,000 ft. to 128 mm. (1/6 
8 Chapter 2. —THE PROBLEM OF REDUCED BAROMETRIC PRESSURES 
atmosphere), so that 5/6 of the atmospheric 
pressure (read density) is concentrated in the 
lowest 8 miles of the 100-mile atmosphere. With 
the decrease in barometric pressure as the alti- 
tude increases there is a corresponding decrease 
in partial pressure of oxygen. Eventually, the 
partial pressure of oxygen gets so small that 
sufficient oxygen necessary for life is not avail- 
able. 
This is true because the partial pressure of 
each component of a mixture of gases is the 
product of the percentage composition times 
barometric pressure, and while at sea level 
(760 mm. Hg.) the partial pressure of oxygen 
in atmosphere is 157 mm. (or an equivalent 
oxygen percentage of 20.93), at 18,000 ft. (380 
mm. Hg.), the partial pressure of oxygen is 
79.3 mm. (or an equivalent oxygen percentage 
of 10.45). Therefore, the passage through the 
lungs, into the blood, of the required amount 
of oxygen essential for living tissue is deter- 
mined by the partial pressure of oxygen in the 
atmosphere, and cannot take place above cer- 
tain altitudes. So, in order to maintain suffi- 
cient oxygen pressure, the percentage of oxy- 
gen in the inspired air must be increased 
(P 02 = % 02 P Air), until finally 100% 
oxygen must be used at high altitudes. 
The table shows the relationship between al- 
titude, barometric pressure, oxygen pressure, 
and oxygen percentage equivalent. 
approximate relationship is true until 35,000 to 
36,000 ft. is reached, whereafter the tempera- 
ture remains rather constant, varying between 
—55° to—65° C. The constant temperature 
zone is called the stratosphere, and this region 
of the atmosphere is free from vapor (and, con- 
sequently, icing problems). The extreme cold 
of high altitude has a direct bearing on physio- 
logic function and will be discussed later. 
Below is listed information concerning vary- 
ing altitudes: 
Altitude Data 
380.000. .. .Maximum rocket flight—normal trajectory. 
360.000. .. .Lower limits of the aurora borealis and 
australis. 
300.000. .. .“Shooting Stars”. 
270.000. .. .Stratopause—lower limit of ionosphere. 
250.000. .. .Noctilucent clouds—upper limit of propa- 
gation of sound in air, since molecules are 
so rare and far apart. 
132.000. ... Sounding balloon flight. 
106.000. .. .Maximum ozone concentration. 
72.000. .. .Record balloon ascent by Captains Ander- 
son and Stevens. 
63.000. .. .Total atmospheric pressure 47 millimeters 
of mercury standard vaporization of fluids 
takes place. 
34.000. .. .Upper limit of normal oxygen saturation 
of blood breathing 100 percent oxygen. 
32.000. .. .Tropopause—average. 
Gasoline boils at —54° C. 
30.000. ... Sky appears purple. 
29.000. .. .Peak of Mt. Everest. 
18.000. .. .Highest human community. 
10.000. Level at which human begins to show 
signs of oxygen lack, breathing ambient air. 
ANOXIA 
Anoxia may be defined simply as a condition 
of oxygen deficiency in the human body. You 
are all familiar with the classical classification 
of the etiology of anoxia outlined as follows: 
1. Anoxic anoxia. 
2. Anemic anoxia. 
3. Stagnant anoxia. 
4. Histotoxic anoxia. 
A more recently advanced classification has 
been promulgated by workers in this field, to 
point out more clearly the etiological factors 
responsible for anoxia. This classification is 
shown as follows: 
1. Environmental anoxia. 
2. Pulmonary anoxia. 
3. Circulatory anoxia. 
4. Histotoxic anoxia. 
Altitude 
(Feet) 
Barometric 
Pressure 
(mm. Hg.) 
Oxygen 
Pressure 
(mm. Hg.) 
02 Percent 
Equivalent 
0 
760 
159.0 
20.96 
3,281 
670 
140.4 
18.40 
6,562 
593 
124.5 
16.40 
9,842 
524 
109.8 
14.50 
10,300 
506 
105.9 
13.00 
16,404 
410 
85.9 
11.30 
18,000 
380 
79.5 
10.00 
22,966 
320 
67.0 
8.80 
28,000 
253 
53.0 
6.90 
34,000 
187 
39.0 
5.16 
40,000 
149 
32.0 
4.20 
42,000 
128 
26.7 
3.52 
50,000 
90 
18.8 
2.40 
The study of the structure of the atmos- 
phere reveals an interesting relationship be- 
tween the altitude and the air temperature. 
Roughly, there is a decrease in temperature of 
2 C° for every 1,000-foot rise is altitude. This 
9 AVIATION MEDICINE PRACTICE 
Both anoxic anoxia of the old classification 
and environmental anoxia of the new are de- 
scriptive of the etiology of the anoxia existing 
under conditions of decreased atmospheric 
pressure. There is simply not enough oxygen 
concentration in the environmental atmosphere 
to sufficiently oxygenate the arterial blood, re- 
sulting in an incomplete oxygen saturation of 
the hemoglobin. 
The reduction of the arterial tension of oxy- 
gen is more serious than the lack of oxygen 
saturation. The velocity of oxidative processes 
has been determined by experimental methods 
to be proportional to the partial pressure of 
oxygen. Also, the increased respirations in- 
duced by this lowered oxygen pressure wash 
out the carbon dioxide of the arterial blood and, 
because of this fact, much reduce the dissocia- 
tion of oxyhemoglobin. In fact, the tissues of 
the body are hampered in three ways in this 
type of anoxia: The rate of oxidation is dim- 
inished because of the lowered partial pressure 
of oxygen in the blood; there is less oxygen 
in the blood than normal; the low carbon di- 
oxide pressure hampers the dissociation of oxy- 
hemoglobin. This is the type of anoxia in which 
we are most interested in aviation, because it 
is this type which our flight personnel will have 
to combat and which we are attempting to help 
them overcome. 
A further classification of anoxia of the an- 
oxic or environmental type may be shown as 
follows: 
Fulminating anoxia.—This is rapidly induced 
by sudden ascents to extreme altitudes without 
oxygen, as in explosive decompression, or in 
breathing high concentrations of inert gases, as 
sometimes happens in our dirigible crashes 
when personnel are caught in high concentra- 
tions of escaping helium gas. Unconsciousness 
may develop in 45 to 90 seconds. This type 
of anoxia resembles asphyxia, but asphyxia is 
not anoxia. 
Acute anoxia.—The difference between this 
type and the above is that the acute anoxia is 
not developed as quickly and is not as severe. 
This is the type of anoxia which you see every 
day in the low-pressure chamber when the sub- 
jects are over 10,000 feet without oxygen. 
While every organ in the body is presumably 
affected in this type of anoxia, the central 
nervous system, the respiratory, and the circu- 
latory systems appear to be affected the most. 
The nature of the effect of this type of anoxia 
will be studied in detail later. 
Chronic anoxia.—This is a condition which 
results from long exposure to high altitudes, 
and even in the acclimatized individual there 
is a dyspnea on exertion. The symptomotology 
of this condition may be stated briefly as prin- 
cipally fatigue. Fatigue develops much faster 
than at sea level and recovery is much slower. 
This condition may also produce degenerative 
changes in some organs. Chronic anoxia is 
rarely seen in aviation because of the infre- 
quency of exposure to predisposing factors and 
universal use of oxygen equipment. 
The effect of anoxia on the blood has been 
studied for many years, and by many different 
investigators, and from this mass of work the 
following conclusions may be drawn. In acute 
anoxia, such as we are dealing with, there is 
some evidence that the number of red blood 
cells is increased rather rapidly in most sub- 
jects—in the matter of an hour or so—and 
probably as a result of contraction of the 
spleen forcing a larger number of the cells into 
the blood stream. 
The effect of anoxia on the heart and cir- 
culation in acute anoxia results in the follow- 
ing changes in the blood vascular system. The 
pulse rate increases, as does the contraction of 
the heart, until the percentage composition of 
oxygen in the alveolar air falls to below 9 per- 
cent. After this critical level the rate may 
remain stationary or decrease, but the minute 
volume output of the heart rapidly falls until 
that time when the anoxia affects the heart 
muscle, when the rate falls rapidly and a cir- 
culatory collapse occurs. 
There is no real evidence that the blood 
pressure changes to a significant degree. In 
cardiac failure one explanation is that the in- 
tramuscular pressure is responsible for the 
maintenance of venous pressure and, conse- 
quently, the venous return to the right side of 
the heart. In the circulatory collapse, accord- 
ing to this theory, the intramuscular pressure 
falls first, followed by the failure of the venous 
return and consequent deficient filling of the 
heart and decrease in the amount of blood the 
heart is able to put into circulation. This is 
10 Chapter 2. —THE PROBLEM OF REDUCED BAROMETRIC PRESSURES 
then followed by a fall in blood pressure, and 
the fast, thready pulse which we are so ac- 
customed to seeing in shock. The pallor and 
sweating are a result of the contraction of the 
peripheral arterioles in an attempt to return 
the peripheral blood to the circulation. 
The respiratory system is profoundly affected 
by lowered partial pressure of oxygen. There 
is a fall in the alveolar carbon dioxide pressure, 
which is due to the increased rate and depth of 
the respiratory movements. The increased rate 
and depth of respiratory excursions washes the 
carbon dioxide out of the alveolar air. This 
results in a fall of 4.2 mm. Hg. of carbon di- 
oxide pressure for each fall of 100 mm. Hg. of 
barometric pressure. (This is disputed by some 
workers.) 
In acute anoxia there is an increase in the 
rate, the depth, and the minute volume of the 
respiration. The respiratory center is evidently 
one of the most sensitive areas to the lowered 
oxygen partial pressure. It is believed by some 
workers that with the decrease in oxygen the 
respiratory center becomes more sensitive to 
the carbon dioxide; which would explain the 
increased rate and depth of respiration. After 
anoxia has progressed to the point where the 
cells of the respiratory center have a markedly 
reduced excitability, respiration may cease. 
Other effects on the respiratory system in acute 
anoxia are a slight depression of the respira- 
tion, while the body recovers from the loss of 
carbon dioxide and while the bicarbonate is 
being reformed in the blood. Some subjects, 
when in the stage of acute anoxia, show a 
change in the pattern of respiration, a periodic 
breathing which resembles the well-known 
Cheyne-Stokes Syndrome. The vital capacity 
is decreased approximately 10 percent at an 
altitude of 15,000 ft. This is probably due to 
the dilatation of the alveolar blood vessels. 
Another system which alters its function dur- 
ing anoxia is the central nervous system. Ner- 
vous tissue is the least capable of withstanding 
oxygen want. In anoxic anoxia the blood ves- 
sels which supply the brain dilate early, but 
because of the lowered oxygen pressure the 
brain has a deficient oxygen supply. At a simu- 
lated altitude of 28,000 ft. experimental studies 
have shown cortical cell changes. Some of 
these changes may be irrevocable. Studies of 
the survival of nervous tissue completely de- 
prived of oxygen, even for a matter of minutes, 
show the pyramidal cells of the cerebral cortex 
are most sensitive, the cerebellar cells next, 
followed by the medullary centers and spinal 
cord, in that order. 
The spinal fluid pressure is increased, as is 
the intracranial pressure. The mechanism for 
producing this pressure is not known, but may 
be due to the increased permeability of the 
capillary walls. 
The entire nervous system is affected ir 
anoxia: the finer judgments and discrimina- 
tions are lost first, followed by a train of events, 
such as increased reaction time, loss of initia- 
tive, and slowness of neuromuscular coordina- 
tion. The after-effects of anoxia are headache, 
fatigue, and slow recovery of finer judgment 
sense. The other organs of the body are also 
affected, but the changes just examined become 
so profound that death would result before 
secondary changes. 
The type of anoxic anoxia which is most 
common in aviation is, of course, that which is 
associated with altitude. The decreasing atmos- 
pheric pressure, with resultant decreasing par- 
tial pressure of oxygen in the inspired air, re- 
sults in a lowered oxygen tension in the ar- 
terial blood. Obviously the degree of anoxia 
is directly related with the degree of lowered 
oxygen tension; which in turn is related to the 
altitude. At an altitude of 10,000 ft. there is 
a moderate or mild degree of anoxia which has 
no telltale effects for the first 4 or 5 hours. 
There are, however, definite subclinical effects 
and the finer, or higher, brain functions are 
dulled. With increase in altitude there is a 
more marked anoxia of such a degree that from 
12 to 15 percent of healthy adult personnel will 
faint or become unconscious within a half-hour 
at 18,000 ft. 
As far as aviation personnel is concerned, 
anoxia, even though it be of low grade and not 
severe enough to cause unconsciousness, is a 
very important condition. Low-grade anoxia 
will affect the nervous system, causing complete 
lack of critical judgment, a lack of motor co- 
ordination, and a false feeling of well-being. 
Overcoming the effects of anoxia forms the 
basis of a very valuable practice in aviation 
medicine, namely, the utilization and training 
11 AVIATION MEDICINE PRACTICE 
Figure 2-1.—Demonstration of anoxia in a lew pressure chamber at the Naval School of Aviation Medicine. The sub- 
jects are in an anoxic state at 18,000 feet. The subject to the left is apathetic. Center subject has fair control 
of his faculties. Subject on the right can no longer complete the co-ordination test. 
in the use of accessory oxygen equipment at 
altitudes over 10,000 ft. The natural lowered 
partial pressure of oxygen is increased artifi- 
cially by the use of such oxygen equipment. 
Thus, by the use of accessory oxygen equip- 
ment, aviation personnel can go from sea level 
to high altitudes day in and day out without 
any deleterious effects of anoxia. 
The importance of anoxia in aviation is so 
great that it is worth our while to reiterate 
salient points in the above discussion. Aviators 
are required to use accessory oxygen equipment 
at all times when flying at or over 10,000 feet 
above sea level, except for short emergency 
periods. Anoxia becomes progressively more 
profound as we ascend above 10,000 feet, 
and at 15,000 feet the blood oxygen saturation 
drops off to as low as 77 percent, and rarely 
exceeds 87 percent. Within this range one finds 
considerable handicap in the performance cf 
any physical or mental activity. Headache, 
slight dizziness, a slight feeling of nausea, 
sluggishness, and a general feeling of heaviness 
may be present; vision is slightly dimmed, and 
a feeling of confusion may exist. The individual 
is partially cyanotic; that is, the nails, lips, and 
12 Chapter 2. —THE PROBLEM OF REDUCED BAROMETRIC PRESSURES 
Figure 2-2.—Progressive anoxia at 18,000 feet. Demonstration in a low pressure chamber at the Nayal School of 
Aviation Medicine. The subject no longer writes his name as instructed, but merely scribbles on the pad. 
ear lobes may range from a light blue to a deep 
purple. As is true in all degrees of anoxia, 
judgment is impaired. 
Above 15,000 feet symptoms of anoxia persist 
and may be intensified; the vision is further 
dimmed and the cyanosis is increased. The 
general feeling may be altered from that of 
weakness and sluggishness to a feeling of well- 
being and gaiety much akin to that associated 
with certain stages of intoxication. Progres- 
sive increase in anoxia results, of course, in 
severe taxing of the body with an increasingly 
degree of malfunction, weakness, stupor, coma 
and death. 
An important condition associated with pro- 
longed flying at 9,000 to 10,000 feet is the 
chronic low-grade anoxia. Flying personnel 
who experience long missions at an altitude of 
between 8,000 and 10,000 feet find themselves 
extremely fatigued, irritable, suffering from in- 
somnia, loss of appetite, and a general insidious 
weakness. This picture does not present itself 
13 AVIATION MEDICINE PRACTICE 
Figure 2-3.—Demonstration of anoxia at 30,000 feet in a low pressure chamber at the Naval School of Aviation Medi- 
cine. Subject is increasingly dull and no longer recognizes the playing cards as he turns them ever. 
14 Chapter 2. —THE PROBLEM OF REDUCED BAROMETRIC PRESSURES 
Figure 2-4.—Subject in low pressure chamber at the Naval School of Aviation Medicine wearing aviator's positive 
pressure oxygen breathing equipment. Type 13 mask, positive pressure regulator and bail-out bottle. 
15 AVIATION MEDICINE PRACTICE 
when personnel use oxygen on prolonged mod- 
erate altitude flights, since by using oxygen the 
accumulated effects of this low-grade, undetect- 
able anoxia are prevented. 
The most efficient method of increasing the 
altitude to which one may safely ascend is 
through the use of supplemental oxygen in the 
inspired air. This oxygen replaces a portion 
of the unnecessary nitrogen, thus increasing 
the oxygen percentage of the air inspired. 
Using one hundred percent of oxygen one is 
able to maintain a normal 96 percent oxygen 
saturation- up to 34,000 feet. Beyond this alti- 
tude, total barometric pressure is so low that, 
regardless of the amount of oxygen in the in- 
spired air, the partial pressure necessary to 
drive sufficient oxygen from the alveoli into 
the blood and maintain normal saturation is 
too small. At 42,000 feet, breathing pure oxy- 
gen, a man is approximately as well off as when 
he is at 18,000 feet breathing ambient air. 
The recent introduction of pressure breath- 
ing equipment (figure 2-4) has increased the 
ceiling of the aviator to even greater heights. 
For many years most physiologists believed 
that under no circumstances must positive pres- 
sure be applied to the inspired air. It was be- 
lieved that damage to the alveoli would inevit- 
ably result. Through actual experimentation in 
recent years by those engaged in aviation phys- 
iological research, it has been demonstrated 
that the average healthy young male adult can 
withstand positive pressure (to the extent of 
10 to 12 inches of water pressure) for an in- 
definite period. As a result of these findings, 
positive pressure breathing equipment has been 
devised which permits an increased oxygen 
flow into the mask, and at the same time in- 
creases the resistance to the flow of expired air 
from the mask. 
This system results in an increase in the oxy- 
gen pressure in the mask, which is transmitted 
through the respiratory passages to the alveoli, 
bringing about an increase in the oxygen trans- 
mission through the alveoli and a consequent 
increase in oxygen saturation of the arterial 
blood. Positive pressure oxygen equipment, 
properly adjusted, permits an individual to 
maintain an arterial oxygen saturation of ap- 
proximately 87 percent at 43,000 feet, which 
is sufficient to maintain normal body functions. 
Above 43,000 feet even with 100 percent oxygen 
and pressure breathing, one rapidly becomes 
anoxic, due to an insufficient oxygen pressure 
in the inspired air. We may safely say, then, 
that the accessory oxygen equipment that is 
now standard in aviation, the absolute safe 
operational ceiling is 43,000 feet. The solution 
to further increased ceiling is the use of pres- 
sure cabins, cockpits, or suits. 
EXPANSION OF BODY GASES 
Gases in the body are present in free and 
dissolved states. Free gases are those present 
in such body cavities as the gastrointestinal 
tract, the paranasal sinuses, and the middle ear. 
The problem of the expansion of free gases in 
the paranasal sinuses and the middle ear is 
covered in the the chapter on aviation otorhi- 
nolaryngology. The expansion of dissolved 
gases in the body at altitude will be discussed 
under the subject heading of aeroembolism. 
The gas found in the intestinal tract is 
largely that which results from the swallowing 
of air; however, some of it is produced by the 
decomposition of ingested food. The variable 
amount of gas present in the gastrointestinal 
tract is always maintained at a pressure ap- 
proximately equivalent to that of the atmos- 
phere surrounding the body. Intestinal gases, 
like all other gases, behave according to the gas 
laws. Therefore, as the individual ascends in 
the atmosphere, the volume of his intestinal 
gas will increase. It has been stated by Arm- 
strong1 that, because they are saturated with 
water vapor, the gases in the intestinal tract 
do not expand, (with ascent), in exact pro- 
portion to the decrease of barometric pressure; 
however, we can safely assume the change in 
relative volume at various altitudes as conform- 
ing to the following table: 
Altitude 
Relative volume of gas 
0 ft. 
1 volume 
18.000 ft. 
2 volumes. 
28,000 ft. 
3 volumes. 
33,000 ft. 
4 volumes. 
38,000 ft. 
5 volumes. 
42,000 ft. 
6 volumes. 
The degree of difficulty encountered by the 
expansion of gases in the gastro intestinal tract 
16 Chapter 2. —THE PROBLEM OF REDUCED BAROMETRIC PRESSURES 
depends upon the amount of gas present and 
the rate of ascent. 
If the ascent does not exceed 300 feet per 
minute, there will be only a feeling of moderate 
abdominal distention at 12,000 to 16,000 feet, 
with associated sensations of the movement of 
gas. Belching and the passage of flatus will 
begin and tends to continue as the altitude in- 
creases. Slow ascent rarely causes incapacitat- 
ing abdominal discomfort, inasmuch as the 
expanded gases can be passed through the tract 
and eliminated. With rapid ascents of 2,000 
feet per minute, or more, the gas expands rap- 
idly and tends to remain localized in the in- 
testinal loops—thus increasing abdominal dis- 
tention—and abdominal cramps of varying 
severity may be experienced. The abdominal 
distention may also be great enough to cause 
upward pressure on the diaphragm and embar- 
rass respiration; it may be of such severity as 
to distract the man from his task or incapaci- 
tate him. A primary type of shock, caused by 
pain stimuli from abdominal distention, has 
been observed in the operation of low-pressure 
chambers. 
A major factor determining the amount of 
gas in the intestinal tract is the quality and 
quantity of food ingested. The following is a 
list of “Diet Don’ts” for flying personnel, par- 
ticularly before engaging in high altitude 
flights: 
1. Don’t gulp food or fluid. 
2. Don’t eat excessively. 
3. Don’t eat gas-forming foods, such as 
beans, cabbage, raw apples, cucumbers, greasy 
meats, and spice. 
4. Don’t drink carbonated beverages, such 
as coca colas, gingerale, etc., or whipped drinks, 
as malted milks, milk shakes, etc. 
In mild cases, passage of gas, or descent 
will ordinarily relieve the distress immediately. 
In severe cases, it is not unusual for the cramps 
to last for 24 hours after descent to sea level 
pressure. Vague, undefined gastro-intestinal 
complaints, (with the attendant abdominal dis- 
tention), have been described as a result of re- 
peated ascents. 
AEROEMBOLISM 
The tissues of the body contain a quantity 
of dissolved gas, held either in a physiochemical 
combination with certain elements or in a pure 
physical state. There are three main dissolved 
gases in the human body: oxygen, carbon di- 
oxide, and nitrogen. Oxygen and carbon dioxide 
are found to be held both in physical and chemi- 
cal combinations, with the greatest amount 
being bound chemically. Nitrogen, being an 
inert gas, is held in solution in the body purely 
by physical pressure. Since nitrogen consti- 
tutes approximately 80 percent of the gas dis- 
solved in the body tissues, and since the amount 
varies with changes in the gaseous tension of 
the environmental air, this gas is most im- 
portant in the problem of dissolved gases in 
the body when large changes in atmospheric 
pressure occur. 
In discussing the cause of this condition it is 
helpful to use an analogy. Almost everyone is 
acquainted with the machine that makes the 
common soda water in soda fountains. It 
consists essentially of a cylinder with piston, 
ordinary water, and a tank of compressed 
carbon dioxide. Water is put in the bottom of 
the cylinder and some of the carbon dioxide 
is allowed to flow into the space above the 
water. The piston is then depressed, and with 
the increase in pressure the carbon dioxide dis- 
solves in the water. As long as this pressure 
is maintained, the carbon dioxide will stay in 
solution. However, if the pressure is decreased, 
either by lifting the piston or by letting the 
soda water flow into the outside air, the carbon 
dioxide comes out of solution. This release 
of pressure is what accounts for the formation 
of bubbles, and the foaming up of carbonated 
drinks, when the bottle cap is removed. Now, 
how does this apply to the human body? 
The human being lives constantly in an at- 
mosphere made up of 80 percent nitrogen and 
20 percent oxygen, at a total atmospheric pres- 
sure of about 15 pounds per square inch. Using 
our example above, we may compare the human 
body with the water in the bottom of the 
cylinder, and replace the carbon dioxide with 
the nitrogen and oxygen of the atmosphere. 
The “piston” (atmosphere) is set to exert 15 
pounds of pressure per square inch. Under this 
pressure a certain amount of nitrogen and oxy- 
gen is dissolved in the human tissues, in a 
manner similar to the solution of carbon dioxide 
in water. Since the body uses the oxygen in 
17 AVIATION MEDICINE PRACTICE 
metabolic processes there is little of this gas 
existing in the free and uncombined form. 
Insofar as the body is concerned, nitrogen is 
an inert gas and exists in the dissolved, un- 
combined form. As the body is taken to alti- 
tudes where the absolute pressure of the at- 
mosphere is decreased or, as in our analogy, the 
piston is raised, the nitrogen comes out of 
solution from the body tissues and fluids in the 
form of nitrogen bubbles. (Thus, at sea level 
pressure, the tissues of the body are always 
saturated with atmospheric nitrogen.) It is of 
interest that nitrogen is more soluble in fats 
and oils than in water and, likewise, in the 
body the fats dissolve five to six times as much 
nitrogen per unit of mass as does the blood 
itself. 
The following is the sequence of events in 
aeroembolism. During ascent in aircraft, or 
in any other situation in which the atmospheric 
pressure is decreased, the partial pressure of 
the body nitrogen is greater than the partial 
pressure of the alveolar nitrogen. The nitrogen 
from the blood diffuses into the alveoli of the 
lungs; the nitrogen of the tissues enters the 
blood stream, and thence into the lung. Thus, 
the body tends to rid itself of its excess (ex- 
panded) nitrogen. If the ascent is slow, and 
the nitrogen in the body can be eliminated 
through the lungs as fast as it comes out of 
solution, no unusual symptoms occur. If, how- 
ever, the pressure is decreased rapidly to at 
least one-half the original pressure, the nitro- 
gen gas will come out of solution with such 
relative rapidity that bubbles will form in the 
tissues, blood, and body fluids. The most likely 
site for bubble formation is body tissue, which 
has high fat content and meagre capillary 
circulation. When bubbles become large enough 
they block off capillaries, which causes a de- 
creased local blood supply. This blocking of 
blood circulation interferes with the normal 
functioning of the local parts, and provokes 
various symptoms. 
The symptoms of aeroembolism are conven- 
iently grouped according to the affected site, as 
follows: 
1. Skin and mucous membranes. 
2. Bones and muscles. 
3. Respiratory system. 
4. Semicircular canals. 
5. Central nervous system. 
The skin and mucous membrane symptoms 
are popularly known as “The itch". These 
symptoms may be classed as paraesthesias, and 
presumably are caused by collections of nitro- 
gen bubbles beneath the skin which irritate the 
sensory nerve endings. These symptoms mani- 
fest themselves in various ways. There may be 
a sandy sensation between the eyelids and the 
eyes. Frequently small bubbles may be seen 
beneath the conjunctiva. There may be sensa- 
tions of cooling or drying of the eyes. A 
generalized itching of the skin may occur, but 
it is more common for one area, (usually near 
a large, subcutaneous deposit of fat, as around 
the waist or on the buttocks) to be affected. 
Scratching is only of temporary relief, since 
the nitrogen bubbles are pushed from one area 
to another. The sensation of ants crawling over 
the body is not uncommon. The sensations of 
excessive sweating when in reality the skin 
is perfectly dry, and of hot and cold flashes, 
also fall in the general group of paraesthesias 
in aeroembolism. 
In some individuals, bubbles of varying sizes 
may be felt or seen beneath the skin and 
mucous membranes, particularly beneath the 
palmar skin of the fingers and beneath the 
ocular conjunctiva. In most cases the symptoms 
disappear immediately upon reaching lower al- 
titudes (increased external pressure). A small 
percentage of cases retain subcutaneous indura- 
tion and erythema for several days. None of 
these symptoms is incapacitating, but they are 
annoying. The occurrence of these dermal 
symptoms indicates the onset of aeroembolism, 
and should warn of the possibility of the de- 
velopment of more severe symptoms. 
Symptoms of the joints and muscles are 
commonly referred to as “the bends". Some 
observers believe the pain in the bones and 
muscles is due to the blocking of capillaries 
supplying the area involved, while others be- 
lieve it is due to the gas (nitrogen) pressure 
on or under the periosteum or the insertion of 
tendons about the joint. While movable joints 
are most commonly affected, pain is frequently 
felt in the region of the biceps and the poster- 
ior thigh muscles. The pain has been grouped 
into four arbitrary types, as follows: 
18 Chapter 2. —THE PROBLEM OF REDUCED BAROMETRIC PRESSURES 
Type 1. An aching in one or more areas, 
which is noticeable but not severe or incapaci- 
tating. 
Type 2. Pain is more severe than type 1, 
and of such a degree that the subject restricts 
his movements. Although this pain is not in- 
capacitating it definitely lowers a man’s 
efficiency. 
Type 3. Pain is more severe than type 2. 
The person is unable to move the member 
affected; he becomes pale, clammy, and if not 
relieved will become unconscious. It is definitely 
incapacitating. 
Type 4. Pain appears with dramatic sud- 
deness, and is very apt to render a man un- 
conscious in a very short time, unless he is 
given immediate relief. 
The bone and muscle symptoms are the most 
common causes of incapacity from aeroembo- 
lism. It is obvious that a pilot or crew member 
who is unable to move his leg or arm is a se- 
rious handicap to any mission. Descent to low 
altitude (greater pressure) effects immediate 
relief in most instances. Although there may 
be some residual effects after recompression 
they are not common. 
The involvement of the lungs in aeroembo- 
lism, popularly known as “the chokes”, is due 
to the collection of nitrogen bubbles in the cir- 
culation of the lungs. These bubbles irritate 
the mucous membranes of the respiratory tract 
and cause burning, substernal pain, an un- 
productive and difficult cough, and a sensation 
of choking. The “chokes” have also been de- 
scribed as “like mixing a bromoseltzer in the 
lungs.” The symptoms increase the individual’s 
apprehension, and may lead to collapse. It is 
definitely incapacitating and relief must be pro- 
vided as soon as possible to prevent serious re- 
sults. Fortunately, the “chokes” are much less 
common than the two groups of symptoms 
described above. Immediate relief without 
residual effect is gotten by descent. 
A condition, popularly known among deep 
sea divers as “the staggers”, may occur in 
aviators. The individual is completely confused 
in regard to position and movement, and be- 
haves, accordingly, much like an intoxicated 
person. This condition is very incapacitating 
and the symptoms may persist for days, but 
fortunately its occurrence is rare in aviation. 
Divers’ “paralysis” is probably due to the 
blocking of cerebral or spinal capillaries, with 
a resultant ischemia to a certain area of the 
brain or spinal cord. Some believe it may be 
due to the direct pressure upon the nerve roots 
of nitrogen bubbles in the spinal fluid. It will 
result in paralysis of that part of the body 
controlled by the part of the brain or cord 
affected. Nitrogen bubbles have frequently 
been demonstrated in the spinal fluid at altitude 
pressures equivalent to that found at 18,000 ft. 
Since the spinal fluid has no direct connection 
with the circulating blood it is probable that 
the nitrogen is not rapidly eliminated. This 
has led some investigators to believe that most 
of the symptoms are due to pressure (from 
these bubbles) on the central nervous system. 
Fortunately, divers’ paralysis is extremely rare 
in aviation. 
In the early days of high altitude bombing in 
the last war, a fairly large percentage of the 
bombers had to return to these bases without 
completing their mission, because personnel 
developed incapacitating symptoms of aeroem- 
bolism. There were three methods open to 
correct this situation: the service could em- 
ploy men for high altitude flying who were 
resistant to the effects of low atmospheric 
pressures (bend resistant) ; the physico-chemi- 
cal state of the body of those who were suscep- 
tible to aeroembolism could be altered to render 
them less susceptible; or, the environment of 
the individual could be controlled so that he 
would not be exposed to low pressures, even 
though flying at high altitudes. 
To aid in the selection of bend-resistant 
personnel, low pressure chambers were oper- 
ated for the classification of individuals accord- 
ing to their ability to withstand the effects of 
low atmospheric pressures, with particular ref- 
erence to the development of the symptoms 
of aeroembolism. Composite test data revealed 
that the younger the individual the less suscep- 
tible he is to the bends. Men in the older age 
groups, who have their valuable experience, 
need not, however, be eliminated from high 
altitude flying (except fighter craft), since by 
altering the physico-chemical state of the body 
a person can become more resistant to bends. 
By breathing 100 percent oxygen, the partial 
pressure of alveolar nitrogen is greatly reduced, 
19 AVIATION MEDICINE PRACTICE 
with a resultant diffusion of nitrogen from the 
blood and tissues and a reduction of the nitro- 
gen stores of the body. This is the principle 
of the process of denitrogenation, or, as it is 
sometimes called 'preoxygenation. According to 
the best available evidence, the elimination of 
about 50 percent of the body nitrogen before 
ascent to high altitude gives most people pro- 
tection from serious or incapacitating symp- 
toms of aeroembolism. Fifty percent of the 
body nitrogen can be removed by breathing 100 
percent oxygen for one hour. 
Since denitrogenation also occurs during 
ascent to high altitudes, and when 100 percent 
oxygen is breathed from the ground on up, 
the degree of nitrogen removal is greatly in- 
creased. 
Denitrogenation, however, is practical in only 
certain types of combat flying, namely, sched- 
uled missions. Bombing and observation plane 
personnel who are scheduled to fly at a certain 
time can begin breathing oxygen long enough 
before that time to insure sufficient denitro- 
genation. Fighter pilots, however, who may 
have to fly at any time, and who must climb 
at maximum rates, find denitrogenation im- 
practical, since it would entail their breathing 
oxygen for long hours while at the ready. 
Therefore, for fighter pilots the first and third 
alternatives only are applicable, that is, choice 
of personnel or alteration of environment. 
By maintaining the body within an atmos- 
pheric pressure more nearly that at sea level, 
even though the plane may be flying in a very 
high altitude, the development of aeroembolism 
can be prevented. That, of course, is the prin- 
ciple applied to the use of the pressure suit or 
the pressurized cabin plane. However, neither 
method is sufficiently developed at present to be 
practical for large scale combat flying. 
Although it is known that nitrogen bubbles 
form in the tissues, and in the spinal fluid at 
18,000 ft., it is rare to encounter any symptoms 
considered incapacitating below 30,000 ft. Prac- 
tically, then, so far as aviation is concerned, 
aeroembolism is a disease that occurs only 
above 30,000 ft. 
The probabilities of developing symptoms de- 
pend upon the rate of climb to the altitude and 
the length of time at that altitude. (Thus, a 
person might be able to tolerate 35,000 ft. for 
an hour, and yet become incapacitated with 
bends after 1 hour and 5 minutes. Also, an 
individual might be able to tolerate 35,000 ft. 
for several hours and yet develop incapacitating 
symptoms shortly after reaching 40,000 feet.) 
They further depend upon the amount of mus- 
cular movement, and the degree of protection 
from cold. Too much movement, and chilling 
both abet the onset of the bends. The general 
physical condition, with special regard to 
fatigue, alcohol, and food, is also a factor. 
OXYGEN EQUIPMENT IN AVIATION 
The development of oxygen equipment in 
aviation has kept pace with the constant im- 
provement of design in modern aircraft. The 
picture in the past has been one of continuously 
increasing efficiency and ceiling in aircraft, 
with a concurrent intensification of physiologi- 
cal difficulties requiring further improvement 
in oxygen equipment. The lack of physiological 
data necessary for the development of aviators’ 
oxygen equipment in the earlier days proved 
a major difficulty to flight surgeons and others 
engaged in aeromedical work. It is only in 
recent years that sufficient knowledge has been 
accumulated of the requirements of man at 
altitude, and that fairly satisfactory accessory 
oxygen equipment has been developed. 
The first oxygen equipment used at altitude 
was that taken along by Tissandier, Croce, and 
Sivel in their historic balloon flight. This con- 
sisted of a container of oxygen with a tube and 
mouthpiece attached. The deficiency of this 
equipment was quite apparent for Tissandier’s 
companions succumbed to anoxia. This tragedy 
of insufficient knowledge and unsatisfactory 
oxygen equipment has recurred many times in 
aviation since then. 
The earliest standard oxygen equipment used 
by the Navy consisted of a high-pressure 
cylinder containing oxygen at 1,800 lbs. per 
square inch, with a reduction valve (that re- 
duced the high pressure to 50 lbs. p.s.i.) leading 
to a pipestem through a rubber tube. This type 
of oxygen supply was very wasteful and, in 
general, unsatisfactory. Inasmuch as only a 
very small fraction of the oxygen was used in 
actual respiration, and because the oxygen 
20 Chapter 2. —THE PROBLEM OF REDUCED BAROMETRIC PRESSURES 
flowed constantly during the expiratory as well 
as the inspiratory phase of respiration, the 
oxygen was depleted rapidly at altitude. The 
pipestem itself was messy and the method pro- 
moted undue salivation. Earlier aviators re- 
ferred to the pipestem as the “slobber tube.” 
Later, in an effort to render the oxygen 
system more economical and sanitary, a face 
mask was devised (replacing the pipestem), 
and a reservoir breathing bag was introduced 
for economy. This rebreather conserved the 
oxygen breathed out from the upper respira- 
tory dead air space and so created greater 
economy. Until better equipment was developed 
it served aviation during the early part of 
World War II as an oxygen-administering 
device. 
Another modification of the constant flow 
principle has been made by using a reservoir 
system composed of a series of check and relief 
valves. By this method, oxygen can be trapped 
in a reservoir during the expiratory phase of 
respiration, and then can be used as a source 
of supply during inspiration, resulting in 
greater economy. 
The constant flow system of oxygen supply 
is more economical at increased altitudes, and 
so the rate of flow of such a system must be 
calibrated with that in mind. This is an appli- 
cation of Boyle’s Law. As pressure drops with 
increasing altitude, the oxygen released occu- 
pies a greater space because of the decrease in 
atmospheric pressure. The increase in volume 
of the gas, with a drop in ambient pressure, 
alters considerably the minute volume respira- 
tory requirements. Thus it is seen that a res- 
piratory pattern at altitude, compared to a 
similar pattern at sea level, will actually receive 
an increasingly reduced quantity of oxygen (al- 
though the sea level volume requirements will 
be constantly met), since the oxygen expands 
when released at ambient pressures. 
As the economy of oxygen became more and 
more important, it was necessary to find new 
methods of administering oxygen. This was 
necessary because of the weight and space oc- 
cupied in aircraft by oxygen equipment. Both 
of these factors were and still are critical in 
aircraft design. Two types of apparatus were 
designed to increase the factors of economy. 
One was called the rebreather. This device is 
a closed circuit oxygen system similar to that 
used in a basal metabolism machine, and prac- 
tically the only oxygen used by the wearer of 
this device is that which he actually consumes 
in his body. The chief difficulty with such a 
device (which proved to be its downfall in 
aviation) was the danger of air entering into 
the system, and the accumulation of carbon 
dioxide within the rebreather. Although this 
device offers the greatest economy, the dangers 
in its use were such that its military application 
was obviated. 
The other alternative in increasing the econ- 
omy of oxygen supply systems for aviators was 
to make a device which would administer oxy- 
gen only during the inspiratory effort, and 
only in sufficient quantity to keep the individual 
normally supplied with oxygen. This meant the 
development of a demand type of system which 
caused the oxygen to flow during inspiration 
only. Since the demand-type system furnishes 
100 percent oxygen at all altitudes, there was 
still considerable wastage of oxygen. 
To correct this waste factor a device was in- 
corporated in the demand oxygen regulator 
permitting air to be sucked in and mixed with 
the oxygen in varying amounts, depending 
upon the altitude. This meant the development 
of an automatic control for diminishing the air 
dilution and increasing the oxygen percentage 
as altitude was gained, and a reserve procedure 
as altitude was lost. Such a device was devel- 
oped and used by the Army Air Forces and 
Navy aviation during the greater part of World 
War II. This device is still being used, but has 
been modified several times to improve it func- 
tionally, decrease its weight, and increase its 
reliability. 
The standard aviators’ oxygen breathing 
equipment used in the Navy at present is a 
system utilizing a diluter-demand regulator at 
ambient pressures, and a system that will, 
when necessary, deliver oxygen under positive 
pressure. 
The diluter-demand system as now used in the 
Navy (figure 2-5) consists of a high-pressure 
oxygen cylinder supply, connected to a diluter 
demand regulator that has a reduction valve as 
one of its integral parts. The regulator is 
designed for use in high altitude flight. It 
automatically mixes varying quantities of air 
21 AVIATION MEDICINE PRACTICE 
Figure 2-5.—Diluter-demand regulator, oxygen flow indicator and pressure gauge, with type 14 mask attached to quick 
release disconnect. 
22 Chapter 2. —THE PROBLEM OF REDUCED BAROMETRIC PRESSURES 
assembly consisting of an oxygen cylinder 
(either 295 cubic inches or 96 cubic inches), 
a diluter-demand regulator and a carrier to 
unite and support the components. The advan- 
tages of this system are: 
1. Its flexibility. The oxygen may be readily 
provided, when needed, for personnel aboard an 
aircraft without a permanently installed oxy- 
gen system, or for extra passengers in planes 
with limited oxygen provisions. 
2. Its weight-saving feature, since practi- 
cally all of the oxygen equipment may be re- 
moved when flights to oxygen altitudes are not 
contemplated. 
As has been previously stated, it is necessary 
to breathe oxygen under pressure if altitudes of 
43,000 feet are to be reached and if the flier 
is to be normally supplied with oxygen. Pres- 
sure-breathing modifications were incorporated 
in the basic demand regulator, as well as in the 
oxygen mask: they included the construction of 
a constant flow attachment in the regulator, 
for use above 34,000 feet, and a variable re- 
sistant expiratory valve in the mask. Modifica- 
tions are still being made in the present day 
pressure-breathing oxygen equipment. Even 
with the use of pressurized cabins and cockpits, 
it is necessary to equip aircraft with oxygen 
equipment, to be used as a safety device should 
pressurization suddenly be lost at high alti- 
tudes, and to permit lower pressurization. 
The positive pressure demand oxygen system 
used in the Navy consists of the following 
articles, (figure 2-9) ; namely, 
1. Type 13 oxygen mask. 
Figure 2-6.—Schematic diagram of a diluter-demand 
oxygen regulator. 
and oxygen, the ratio depending on the altitude, 
and delivers the quantity demanded upon in- 
halation. The mixing device may be cut out 
and 100 percent of oxygen delivered on inhala- 
tion, or the entire valve may be by-passed by an 
emergency by-pass and 100 percent of oxygen 
delivered at a continuous rate. The diluter- 
demand type delivers oxygen at the ambient air 
pressure; therefore, above 30,000 feet, 100 per- 
cent oxygen. 
The standard Navy mask used with this type 
of equipment is the type 14 oxygen mask. 
In certain passenger, cargo, bomber, and 
patrol airplanes, there is a definite need for an 
individualized oxygen system utilizing the 
standard diluter-demand oxygen regulator, and 
permitting rapid installation and removal 
where flights to oxygen levels are made only 
occasionally. There is available a compact 
23 AVIATION MEDICINE PRACTICE 
Figure 2-7.—Type 14 oxygen mask for use with standard dilufer-demand aviator's oxygen equipment, 
2. The positive pressure demand oxygen 
regulator with the attached bail-out interlock. 
3. The high pressure oxygen reducer. 
4. The bail-out assembly. 
The type 13 oxygen mask (figure 2-10) differs 
from the type 14 oxygen mask (now in current 
use in the Navy) in its method of suspension 
and also by having oxygen inlet check valves 
and a compensated exhalation valve. 
The two inlet check valves are small rubber 
flapper valves placed over each of the oxygen 
inlet ports. These valves function in such a 
manner that upon exhalation they are closed, 
thus shutting off the flow of oxygen into the 
mask from the regulator. 
The compensated exhalation valve is a valve 
24 Chapter 2. —THE PROBLEM OF REDUCED BAROMETRIC PRESSURES 
which permits exhalation from the mask. This 
valve is so designed that, in ordinary demand 
use, upon exhalation the valve opens, allowing 
the gases to escape from the mask through the 
exhalation port, as in the ordinary demand 
oxygen masks. When positive pressure is being 
used this valve, through a communication with 
the oxygen inlet tube, requires the wearer to 
exert (during exhalation) a slightly greater 
amount of pressure within the mask than the 
Regulator Setting 
Thousands of Feet 
Pressure 
Inches of Water 
35 
1 
40.5 
2 
41 
4 
41.5 
6 
42.5 
8 
43 
10 
These settings should be used at the altitudes 
Figure 2-8.—Standard Navy Aviator's portable oxygen equipment, 205 eu. inch and 96 eu. inch oxygen bottles, 
positive pressure being delivered to the mask 
by the regulator. In this manner the pressure 
in the mask is kept fairly constant both in 
inhalation and upon exhalation. 
The positive pressure demand oxygen regula- 
tor (figure 2-9) is a chest-worn type of regula- 
tor and acts as any other demand regulator if 
the pressure setting on the dial is maintained at 
the off position. It will be noted that on the 
control knob of the regulator there is a scale 
which gives pressure settings for certain alti- 
tudes. These regulator settings deliver pres- 
sures to the mask and lungs as follows: 
indicated, and if the pilot does not feel properly 
protected with this pressure setting he may in- 
crease the setting to the next higher setting. 
This regulator is suspended from the neck by 
an adjustable strap, and this strap should be 
so adjusted that the smaller strap at the bottom 
of the regulator may be placed around the 
cross-chest strap of the parachute harness. In 
this manner the regulator is kept from swing- 
ing around the body, on movement. It should 
be remembered that when the dial reads in the 
off position the regulator functions as a normal 
demand oxygen regulator. 
25 AVIATION MEDICINE PRACTICE 
Figure 2-9.—Navy positive pressure oxygen breathing equipment for high altitude use. Equipment consists of the type 13 
oxygen mask, positive pressure regulator, bail-out bottle and test valve for the bail-out bottle. 
26 Chapter 2. —THE PROBLEM OF REDUCED BAROMETRIC PRESSURES 
Figure 2-10.—Type 13 oxygen mask for use with positive pressure oxygen systems for aviators. 
Attached to the bottom of the regulator is 
the “bail-out” interlock assembly. This inter- 
lock permits disconnection of the regulator 
from the oxygen supply of the plane; upon 
such disconnection the “bail-out” cylinder auto- 
matically provides oxygen, without necessity 
for any other action on the part of the pilot. 
In other words, by merely disconnecting from 
the airplane supply the flow is continued auto- 
matically from the “bail-out” cylinder. 
The “bail-out” bottle assembly (figure 2-9) 
consists of a 30.5 cu.in. bottle containing oxy- 
gen at 1,800 p.s.i., a reducer and a high pres- 
sure gauge, and also a quick disconnect fitting. 
The entire assembly described is held in a con- 
tainer which permits carrying of the assembly 
on the thigh. 
Because there are hazards in the use of oxy- 
gen equipment, certain precautions must be 
taken to avoid its faulty operation. It is neces- 
sary that the oxygen be dry, for if it were 
moist condensation might take place in the fine 
orifices of the oxygen regulator; and since the 
upper atmosphere is cold, freezing might take 
27 AVIATION MEDICINE PRACTICE 
Figure 2-11.—Navy high pressure oxygen bottles for use In aircraft oxygen systems. Bottles are S04 cu. inch, 205 eu. 
inch and 96 cu. inch capacity. 
place with a cessation of oxygen flow through 
the regulator. There is also considerable con- 
densation of moisture from the expired air 
which collects in the oxygen mask. This con- 
densation, at low temperature, might cause the 
masks to freeze and thereby close the inlet ori- 
fices, stopping the oxygen flow from the regula- 
tor into the mask. The expiratory valve might 
also freeze, preventing exhalation of air from 
the mask. 
The mask must also be properly fitted to the 
individual face, to avoid the danger of inboard 
28 Chapter 2. —THE PROBLEM OF REDUCED BAROMETRIC PRESSURES 
leakage of outside air into the mask; this would 
dilute the oxygen concentration of the inspired 
air. Such inboard mask leakages are not im- 
portant until an altitude of 30,000 feet has 
been reached. Since the total atmospheric pres- 
sure, and hence the partial pressure of oxygen, 
becomes so low at altitudes in excess of 30,000 
feet, any dilution with outside air would prove 
dangerous. Oxygen regulators must be care- 
fully checked, at frequent intervals, to insure 
their delivering the proper concentrations of 
oxygen at all altitudes. Care must also be exer- 
cised in the upkeep of the mask. The mask 
should always be kept clean, and should be re- 
placed when it has lost its original shape and 
proper fit. 
We have spoken only of one type of oxygen 
source being carried in aircraft, that of gaseous 
oxygen under high pressures in metal cylinders 
(figure 2-11). The standard Navy high-pressure 
cylinders are shatter-proof, as demonstrated 
throughout the War. The Air Force uses low- 
pressure containers of the magnitude of 400 to 
500 pounds p.s.i. in shatter-proof bottles. These 
have the advantage of lightness, but are con- 
siderably greater in volume. There is another 
source of oxygen, for use in aircraft, which 
permits both economy and a decrease in space 
and weight of the oxygen source. This is oxy- 
gen in liquid form, which can be readily con- 
verted into gaseous oxygen in an airborne con- 
verter and then conveyed through the usual 
oxygen systems to the regulators. Since one 
liter of liquid oxygen, when converted, will 
furnish 800 liters of gaseous oxygen, consider- 
able space and weight may be saved by using 
it. 
The development of liquid oxygen has not 
yet reached the stage where it is practical for 
use in all aircraft. Its tendency to “flash off” 
while stored in a converter causes considerable 
loss of oxygen, whether the system is in use or 
not. In its present stage of development it is 
most suitable for the multiengine type of air- 
craft. If the handling of the liquid oxygen can 
be timed so that it is placed in the aircraft 
converter just before the take-off, then one 
could take advantage of its space, weight, and 
duration economy. 
TEMPERATURE VARIANTS IN 
AVIATION AS A PROBLEM 
The temperature range to which a man may 
be subjected, when flying at various altitudes 
and in different climates, may extend from 140° 
to minus 70° F. Since the production of heat 
and the regulation of body temperature are 
essential for normal living, environmental tem- 
perature becomes of great concern in aviation. 
As stated earlier in this chapter, there is a 
decrease in temperature of 2° C. for every 
1,000 foot rise in altitude until the 35,000 foot 
level is reached, whereafter the temperature 
remains rather constant, varying between—55° 
to —65° C. The problem of cold, therefore, 
becomes a real one when flying at extreme alti- 
tudes. The loss of heat to the human body 
occurs through the physical means of radiation, 
convection, and conduction, and a small amount 
through respiration. The heat loss rate is fre- 
quently accelerated by wind blasts from open 
hatches or ports in the aircraft. The proper 
use of clothing is man’s main method for con- 
trolling heat loss. Because of the above-men- 
tioned factors and because of the wide range 
of temperatures encountered in aviation, ade- 
quate clothing for flying personnel is an im- 
portant consideration. There are two types 
of clothing worn by aviation personnel. One is 
the unheated, heavy, bulky type, which has 
both good and bad points. It requires no source 
of heat energy other than that produced by the 
body itself. If a man is forced down in cold 
climates, he continues to have adequate protec- 
tion. On the other hand the excessive weight 
of such clothing, when worn on the ground be- 
fore flight, is apt to cause perspiration, which 
may increase the sensation of cold at high 
altitudes. Because of its bulk, movement is 
restricted and flying efficiency is lowered. 
The other type of clothing is electrically 
heated. This clothing consists of a light leather 
or cloth coverall, with electrical heating ele- 
ments in the lining. For heat production, this 
clothing requires an external source of energy, 
which comes from the electrical system of the 
aircraft. It is light and therefore does not 
restrict movement in the air or cause preflight 
overheating. The fault of this type of clothing 
29 AVIATION MEDICINE PRACTICE 
Figure 2-12.—Subjects receiving instruction in the handling of oxygen equipment during a chill run in a lew pressure 
chamber. Navy standard aviator's cold weather shearling clothing is being worn. 
lies in the possibility that power failure will 
eliminate the source of energy for heating it. 
Too, should the aircraft be forced down in a 
cold climate, the individual would be inade- 
quately protected for survival. 
Cold has certain physiological and psycho- 
logical effects upon the individual. The drop in 
environmental temperature brings about an 
increase in metabolism, muscular tone, and 
muscular activity in the form of shivering. 
The early chilly sensations, as the exposure to 
cold becomes more severe, change to a definite 
sensation of discomfort as the compensating 
mechanisms prove inadequate. This sense of dis- 
comfort results in a decrease in touch sensitiv- 
ity, in muscular reaction, and in coordination. 
The muscles assume a state of tonic contrac- 
tion, which hampers the free movement of the 
extremities. Peripheral circulation decreases in 
the extremities because of vasospasm, and with 
severe vascular changes one may encounter 
tissue anoxia, resulting in tissue destruction. 
The lower temperature increases the oxygen 
consumption. This factor, together with the 
diminished oxygen supply, increases the tend- 
ency for tissue destruction. Anoxic failure may 
result from the establishment of a vicious cycle 
wherein the body reaches higher and higher 
altitudes and demands more and more oxygen, 
and at the same time enters an environment 
which has a diminishing partial pressure of 
oxygen. 
30 Chapter 2. —THE PROBLEM OF REDUCED BAROMETRIC PRESSURES 
A flier’s emotional state is also affected by 
cold. Muscular incoordination, which limits his 
ability to control his aircraft properly and the 
psychological reaction to physical discomfort, 
result in a loss of morale. With the deteriora- 
tion of physiological responses of the body, 
panic, indifference, and finally stupor may 
result. 
Frostbite.—Actual destruction of tissues, as 
seen in cases of frostbite, have in the past been 
common among aviation personnel. It is neces- 
sary to keep the extremities warm and pro- 
tected from the cold wind blasts to avoid 
ischemia, that results from vasospasm. In- 
doctrination to the hazards of low temperature 
and frostbite, together with first aid proce- 
dures, is necessary for all flying personnel. 
The environmental temperature, especially 
that at high altitudes, must be taken into ac- 
count in the use of oxygen equipment. Caution 
must be exercised and constant checking car- 
ried out to avoid freezing of equipment, particu- 
larly since expired breath is always vapor- 
charged. 
The problem of extremely high temperatures 
has so far been fairly well controlled only at 
the lower altitudes. In a cockpit the pilot 
is quite well protected from external ambient 
temperature, but with a large canopy he be- 
comes subjected to increased radiant heat. 
Where suitable cooling methods were not avail- 
able, cockpit temperatures as high as 150 de- 
grees F. have been reported, which resulted in 
the blistering of the pilot’s hands when at- 
tempts were made to operate the controls. 
Cooling systems involving the rapid expansion 
of compressed air have been installed to control 
this rise in temperature due to radiant heat. 
These systems have their drawbacks, especially 
in regions where high humidity prevails. Here 
the expanding air may condense the vaporized 
water and deliver it to the cockpit as a small 
snowstorm, with a consequent reduction in visi- 
bility. 
The protective element of the atmosphere in 
absorbing radiant energy decreases markedly 
as greater altitudes are reached. In a closed 
cockpit this may result in considerable increase 
of heat in the plane. Skin friction produced by 
the higher speeds reached by present day air- 
craft is another source of heat. Aircraft en- 
gineers estimate that the skin friction tempera- 
tures generated by newer aircraft will be in 
excess of the melting point of all known 
plastics. Temporarily, this will necessitate a 
return to glass for canopies and windshields, 
constituting a step backward in the matter 
of pilot safety in the case of an accident. The 
present temperature problem is, as discussed 
in this chapter, a twofold one; protection from 
ambient cold at high altitudes and protection 
from radiant and frictional heat. 
NOXIOUS GASES IN AVIATION 
The noxious gases that are exhausted from 
an operating internal combustion engine create 
an important problem in aviation medicine. The 
most important and deadly constituent of en- 
gine exhaust gases is carbon monoxide. Other 
gases and particles in exhaust vapors are 
present in such small quantities and are so 
much less toxic than carbon monoxide, that 
they are of little practical importance. Exhaust 
gases contain carbon monoxide, carbon dioxide, 
methane, butylene, nitrogen, oxygen, hydrogen, 
water, and various aldehydes including acrolein, 
methyl, ethyl aldehydes, and paraformaldehyde. 
Carbon monoxide varies from 1 percent to 7 
percent in exhaust gases, with an average of 
3 percent. The amount varies with the octane 
rating of the fuel, the fuel air ratio, the throttle 
setting, and the altitude. 
Since, as stated above, carbon monoxide is 
the most deadly constituent of exhaust gases, 
the major portion of this discussion will be 
on the physiological effects of this gas. The 
hazard of carbon monoxide contamination is 
much greater in the single-engine plane than in 
the multiengine plane. This is due to location 
of the engine in the single-engine plane directly 
in front of the fuselage, where the propeller 
blast forces the exhaust gases under and about 
the cockpit. Earlier single-engine planes with- 
out exhaust collector rings were completely en- 
veloped in a cocoon of exhaust gases, as demon- 
strated when a smoke-producing oil was in- 
jected into the carburetion system. With the 
advent of exhaust collector rings the exhaust 
gases were deflected to the sides and below the 
fuselage. There is a constant danger of con- 
tamination, however, in single-engine planes AVIATION MEDICINE PRACTICE 
should the sealing of the cockpit be unsatis- 
factory. The cockpit air is generally at a 
slightly negative pressure to that of the air 
surrounding the plane. Consequently, exhaust 
gases will seep into the cockpit and remain 
there if the cockpit is closed, but incompletely 
sealed. A major source of cockpit contamina- 
tion in the past was from exhaust gases seeping 
through the tail-wheel opening, thence through 
the fuselage and into the cockpit through cracks 
around the fire wall in back of the pilot. Proper 
sealing of the single-engine cockpit eliminates 
the danger of exhaust contamination. 
In the multiengine plane, exhaust contamina- 
tion remains a danger because of the possible 
entry through wing passages, ventilating air 
scoops, and other design features. Exhaust 
cabin heaters are also a possible source of 
contamination if leakage occurs. The danger of 
exhaust contamination is less in pressurized 
cabins provided the carbon monoxide is not 
recirculated by the ventilating system. 
The toxic action of carbon monoxide is 
essentially through its effect on the blood, 
where it produces a deficiency of oxygen in the 
body. Unlike most poisons, carbon monoxide in 
lesser concentrations does not have a direct 
effect on the cells of the body, but in high con- 
centrations it has a toxic effect on the respira- 
tory enzymes of the cells. In the concentration 
generally encountered the effect is primarily on 
the red blood cells, actually interfering with the 
transportation of oxygen from the lungs to the 
tissues. If elimination is soon enough and the 
concentration not too great, permanent damage 
does not result. The hemoglobin molecule takes 
up carbon monoxide in the same way that it 
does oxygen, forming carboxyhemoglobin. At 
body temperature its affinity for carbon monox- 
ide is 210 times greater than oxygen. To make 
the situation more serious, the presence of 
carboxyhemoglobin tends to make the remain- 
ing hemoglobin bind to its oxygen more ten- 
aciously, so that it does not give it up to the 
tissues readily. 
The variables that determine the quantity 
of carbon monoxide taken up by the blood are: 
the concentration of the carbon monoxide, the 
duration of exposure, and the degree of activity 
of the individual. Obviously, the first two need 
no explanation. There is a more rapid absorp- 
tion of carbon monoxide, with an increased 
respiratory and circulatory rate, from increased 
activity. 
The initial effects of carbon monoxide poison- 
ing are produced by the developing anoxia. 
These are insidious and consist primarily of 
inattention, reduced concentration, slight mus- 
cular incoordination, and sleepiness. While 
these symptoms are not permanently injurious 
to health, they are dangerous to flying person- 
nel and may result in serious accidents. Head- 
ache is the most prominent symptom up to 30 
percent concentration, and beyond 30 percent 
concentration the impairment of behavior is 
generally quite extreme. 
Symptoms: 
Percent COHb: 
0-10—No subjective symptoms. Visual im- 
pairment by objective tests. 
10-20—Tightness across forehead, slight head- 
ache, dilatation of cutaneous blood vessels. 
20-30—Headache with throbbing in temples. 
30-40—Severe headache, weakness, dizziness, 
dimness of vision, nausea and vomiting, col- 
lapse. 
40-50—Same as preceding, but more severe. 
50-60—Loss of consciousness, irregular res- 
piration, rapid pulse, coma, with intermittent 
convulsions. 
60-80—Coma, convulsions, depressed heart ac- 
tion, respiratory failure, and death. 
Under normal conditions the time required 
to reduce the carbon monoxide in the blood is a 
matter of hours. In a man at rest, the average 
time for the percent of carboxyhemoglobin to 
fall one-half its value is 4 hours. Breathing 
pure oxygen reduces the time from 4 hours to 
40 minutes. Combining 5 percent of carbon 
dioxide with the oxygen produces an even more 
rapid elimination of carbon monoxide because 
of its stimulation to respiration. 
Rate of carbon monoxide elimination at sea 
level. 
30 to 25 percent 
1 
hour 
25 to 20 percent 
20 to 15 percent 
2 
hours 
15 to 10 percent 
10 to 5 percent 
3-5 
hours 
30 to 5 percent 
Flight crews who suspect the presence of 
carbon monoxide or any exhaust gases should 
32 Chapter 2. —THE PROBLEM OF REDUCED BAROMETRIC PRESSURES 
breathe 100 percent oxygen by turning off the 
diluter-demand feature in their oxygen equip- 
ment. 
The maximum allowable limits of carbon 
monoxide in aircraft has varied in the Navy 
from .002 percent to .01 percent, depending 
upon the wartime exigencies. Most physiolo- 
gists agree that the maximum should never ex- 
ceed .0025 percent. Since carbon monoxide does 
nothing but harm to the body, 0 percent is 
the ideal maximum. 
Other harmful noxious gases present in avia- 
tion are: 
1. The vapors from oil after contact with 
heated parts of the engine. These may cause 
irritation to the eyes and respiratory tract and 
result in headache, nausea, and vomiting. 
2. Hydraulic fluids sprayed from breaks in 
lines may cause similar symptoms, 
3. Gasoline vapors absorbed through the 
lungs may effect the nervous system in a man- 
ner similar to alcohol, 
4. The exhaust gases from jet assisted take- 
off units contain carbon monoxide and a fairly 
large percentage of hydrochloric acid. 
The elimination of noxious gases as a danger- 
ous factor in aviation may be outlined as fol- 
lows : 
1. Aircraft designed so that exhaust gases 
do not enter the cockpit or cabin. 
2. A system of regular inspections for breaks 
in firewalls, exhaust heaters, gasoline heaters, 
etc. 
3. The training of flight personnel to realize 
the possibilities of exhaust contamination, and 
the instruction of flight personnel to put on 
their oxygen equipment, with the diluter off, 
immediately upon suspecting such contamina- 
tion. 
PRESSURIZED EQUIPMENT AND 
EXPLOSIVE DECOMPRESSION 
In present-day and future aircraft design 
the intention is to attain altitudes in excess 
of 43,000 feet. If human beings are to fly in 
aircraft at such altitudes, they will need addi- 
tional protection from decompression. The na- 
ture of the protection to be afforded centers 
around the application of increased air pres- 
sure in the immediate environment of the 
human being. Devices for such protection are 
pressurization of the cabin or cockpit in which 
the individual flies or a pressurized suit. 
By the use of such devices, it is possible to 
maintain pressures higher than the ambient 
atmospheric pressures found above 43,000 feet. 
If the cabin, cockpit, or suit is pressurized to 
the extent that the environmental pressure 
about the human being is equal to an altitude 
of less than 10,000 feet, extra oxygen is not 
necessary. If the pressures are less than that 
corresponding to an altitude of 10,000 feet and 
range from 10,000 to 43,000 feet, then extra 
oxygen must be supplied and precautions taken 
against the occurrence of decompression illness. 
In the construction of an aircraft the instal- 
lation of a positive pressure cabin or cockpit 
entails added weight to the aircraft and numer- 
ous technical difficulties in design and con- 
struction. This added weight may modify the 
performance of aircraft both in its duration of 
flight and performance during flight. The seal 
for the cabin or cockpit must be such that the 
pressurizing equipment will be able to maintain 
given pressure and ventilate such spaces at 
a proper rate. There is always the danger of 
a large leak, produced by damage to the seal 
of the compartment, which makes it impossible 
for the pressure to be maintained. A sudden 
loss of pressure results in a change of baromet- 
ric pressure to the individual which is spoken 
of as explosive decompression. Such a rapid 
decompression may result in serious symptoms 
if it covers a fairly wide range of pressure. 
The dangers of explosive decompression in- 
volve the areas of the body in which there are 
large quantities of air. These areas are the 
intestinal tract, the lungs, the sinuses, and the 
middle ear cavity. Since the middle ear and the 
sinus cavities have free access to open air, 
little if any injury would result in these areas. 
If the glottis is open and the individual is 
breathing in the expiratory phase of respira- 
tion, the expanding lung air as a result of 
sudden decompression would vent itself easily 
to the outside. However, in the inspiratory 
phase of respiration, or with the glottis closed, 
serious damage might result to the parenchyma 
of the lung by the sudden expansion of the 
intrapulmonary air. The sudden expansion of 
intestinal gas might be painful and produce 
33 AVIATION MEDICINE PRACTICE 
a shock-like reaction if the individual was un- 
able to permit the escape of the expanding 
gas. There might also be a sudden thrust 
against the diaphragm, pushing it upward 
(simulating a sudden violent expiratory effort). 
Since the expansion of the air in the lungs 
would simulate a sudden violent inspiratory 
effort, these two conflicting events would bring 
about apnea. If one is suffering from lack of 
oxygen during such an explosive decompression, 
the superimposed apnea would increase the 
anoxia. Actually the hazards of explosive de- 
compression are not great, and in experiments 
with human beings as well as with animals, 
explosive decompression from sea level or a low 
altitude to a pressure altitude of 50,000 and 60.- 
000 feet has been well tolerated as long as 100 
percent oxygen under pressure is furnished to 
the individual. 
If aviators are to be safeguarded against 
anoxia as a result of explosive decompression, 
aircraft should have available for the use of 
occupants pressure-breathing oxygen equip- 
ment or pressure suits in the event of such 
decompression. Such devices would safeguard 
the individual and bring about a greater chance 
of survival at altitudes in excess of 43,000 feet, 
should cabin or cockpit pressure be lost. 
To maintain the pressure in pressurized cab- 
ins, and at the same time to provide fresh air 
for ventilation, the usual procedure is to pump 
air into the cabin continuously and allow the 
excess to escape through a valve. This valve is 
set to open only when the internal pressure— 
or when the difference between internal and 
external pressure — reaches a predetermined 
level. The amount of air pumped per minute 
then depends on the requirements for ventila- 
tion. 
In a closed space, such as exists under these 
circumstances, it is important that the condi- 
tioning of the air be adequate for physiological 
efficiency. If a system such as that described 
above, (in which air is continually pumped in 
and allowed to escape), is used the volume of 
air needed per minute depends mainly on the 
quantity required for maintaining proper hu- 
midity. This requirement is greatly in excess 
of the ventilation needed to compensate for the 
rate at which oxygen is used up, or to wash out 
carbon dioxide, cabin and body odors, and so 
forth. The inlets for air to the pumps must 
be carefully placed to avoid contamination with 
carbon monoxide from engine exhaust gas. 
QUESTIONS 
The following review questions on problems of re- 
duced barometric pressures should be helpful: 
1. What are the physical characteristics of the at- 
mosphere that limit flying to relatively low altitudes ? 
2. Explain Boyle’s Law. Dalton’s Law. 
3. Outline the symptomatology encountered in the 
relative stages of anoxia at 10,000, 15,000, 25,000 feet. 
4. What are the limits of positive pressure measured 
in inches of water which may be applied to the lungs 
of the average young adult and how much added ceiling 
will this pressure give him? 
5. Explain the problem of free gas expansion in the 
body at altitude. 
6. How may disability due to free gas expansion be 
avoided ? 
7. Above what altitude is aeroembolism a major 
physiological factor? 
8. Explain preoxygenation for aeroembolism pro- 
phylaxis. 
9. Explain the principle of the diluter-demand oxy- 
gen regulator, 
10. Why does anoxia become progressive even when 
100 percent oxygen is used above 34,000 feet ? 
11. What is the temperature in the stratosphere 
and above ? What is the rate of progressive decrease 
in temperature ascending above sea level ? 
12. What are the two types of cold weather clothing 
used in naval aviation ? 
13. Explain why carbon monoxide is a danger in 
aviation ? 
14. What is the desired maximum allowable limit 
in carbon monoxide concentration in aircraft? 
15. Describe a pressure cabin. 
16. What is the major danger to personnel in ex- 
plosive decompression to 50,000 feet? 
BIBLIOGRAPHY 
1. Principles and Practice of Aviation Medicine. 
Armstrong. 
2. Human Factors in Air Transport Design. McFar- 
land. 
3. Anoxia; Its Effect on the Body. VanLiere. 
4. Compendium of Aviation Medicine. Ruff and 
Strughold. 
5. Naval aircraft oxygen equipment handbooks and 
publications. 
34 CHAPTER 3 
THE PROBLEM OF ACCELERATION * 
The term acceleration as applied to aviation 
medicine requires the consideration of several 
factors, including the kind of acceleration, its 
magnitude, duration, and direction. The kinds 
of acceleration are linear, radial, and angular. 
Linear accelerations of greatest concern to 
aviation medicine are of very short duration 
and high magnitude, as evidenced in aircraft 
crashes. 
Radial accelerations are encountered in the 
turning and maneuvering of aircraft or in the 
tumbling of ejection seats or capsules upon re- 
lease from the aircraft. Radial accelerations 
are of lesser magnitude generally, of longer 
duration, and are of interest principally be- 
cause of the effect of the resultant forces on 
the fluid elements of the body. In this connec- 
tion, the position of the pilot’s body is very 
important and the terms positive, negative, and 
transverse are used respectively to designate 
whether the force is acting from head to foot, 
from foot to head, or at right angles to the 
long axis of the body. 
Angular accelerations are of low degree and 
long duration and involve rotation about the 
long axis of the body, with resultant stimula- 
tion of the vestibular system; thus, they may 
confuse and disorient the pilot. 
To understand the physiological effects of 
acceleration, and thereby the accelerative 
stresses developed in aviation, a brief review 
•of the physics of acceleration is of value, 
ft 
Velocity (V) = —1. As long as V is uni- 
sec. 
form no apparent changes are developed within 
the body. This is best demonstrated by the fact 
that as a part of the earth we, as individuals, 
travel through space around the sun at about 
18 miles per second. In so doing we experience 
no particular sensations referable to such trav- 
el. Acceleration, by definition, is a change in 
velocity. Since velocity, however, is a vector 
quantity, this change may be one either of 
magnitude, or speed, or direction. For a body 
in constant motion, acceleration either in speed 
or direction requires the application of a force 
to the body. In its simplest form this force 
may be defined as F — mx <x, where F = 
force in pounds, m = mass of the object in 
pounds and oc = the acceleration imparted to 
the object in feet per second per second. 
When the earth’s gravity force is the force 
used, the mass and weight of objects are 
W W 
numerically equal; for F = — where — = 
weight at 1 g or under a force equal to the 
pull of gravity. If a force produces an accelera- 
tion twice that of gravity or 2 G, this becomes 
W 
F = — x 2g. Thus F = 2W or the force 
9 
effectively doubles the weight of the object. 
More specifically, the force doubles the effective 
weight of the object. This relationship is the 
basis for the chosen unit of acceleration force, 
which is 1 g or the force of gravity. If a 
known acceleration is divided by 32.2 ft/sec2, 
the acceleration of gravity, F = mg where g 
is the force in terms of gravity. Although it is 
of a constant mass, the object will have an 
effective weight proportional to the g, i.e. 10JF 
for 10 g. 
Changes of velocity in regard to speed are 
defined as linear accelerations and may be 
either increases or decreases. Common ex- 
amples of this type of acceleration seen in 
aviation are take-off, landing (both accentuated 
on aircraft carriers by catapults and arresting 
cables), the opening of a parachute, the con- 
tact of a parachuter with the ground, crashes, 
* Prepared by F. R. Stauffer, LT (MC). USN 
35 AVIATION MEDICINE PRACTICE 
and, more recently with high speed planes, mid- 
air engine failure. 
The type of physiological change incident to 
such an acceleration is common to almost every- 
one. In low magnitude they are reproduced 
by stops and starts in elevators or jumps from 
small heights. In greater magnitude they are 
met in impacts following falls from greater 
heights and the common tragedy of automo- 
bile collisions. If it is appreciated that all body 
tissues and structures are held together by 
varying cohesive and adhesive forces, the ef- 
fects of such accelerations may be easily under-; 
stood. As long as the force producing the ac- 
celeration is applied uniformly to all parts of 
the body, no detrimental action occurs. 
This is best seen in an aviator’s free fall 
following bail-out from an airplane and prior 
to his parachute’s opening. Here, under the 
force of gravity producing an acceleration of 
32 feet per second per second, he experiences 
no changes referable to such acceleration. 
When, however, an accelerating force is ap- 
plied unevenly, certain stresses are immediately 
imparted to the body. These, if great enough, 
may exceed the normal intertissue tensions and 
result in the lacerations, contusions, torn mus- 
cles and ligaments, and even fractures which so 
frequently are seen in falls and collisions. The 
unevenness of application may be shown by the 
example of a simple fall. That part of the body 
striking the ground first will begin to decelerate 
while the rest of the body continues to fall. 
This results in extensive compression of the 
tissues striking first. 
To cite another case, restraining shoulder 
straps, during a crash, will decelerate a pilot’s 
thorax, with some chest compression, while the 
undecelerated head continues forward. This 
will strain the ligaments and vertebrae in the 
cervical area. The same pilot, also, if his head 
strikes some irregular structure within the 
cockpit, will experience localized deceleration of 
the head, with a possible compression fracture 
or even a penetrating wound of the skull. 
Since the normal tissue tensions are fairly 
high, fairly high accelerative or decelerative 
(slowing) forces are necessary to effect body 
changes. The time necessary for these forces 
to act to accomplish their results is, however, 
short, because the body changes, once produced, 
tend to be permanent until medical repair is 
instituted. These crash injuries are, therefore, 
most commonly associated with high forces, 40 
g or more, acting for a short time (small frac- 
tions of a second). 
Protection against this kind of g force may 
be obtained in several ways. It has been cal- 
y 2 y 2 
culated that g = 32 2 x 2d ~ w^ere anc* 
V2 are the initial and final velocities and d is 
the distance covered during the acceleration. 
In crashes, for example, where V2 = O, this 
V2 
reduces to G — Consequently, if d can 
0£i,s-i X LjCjL 
be increased, a given V will produce less g. 
An airplane making a belly landing on a flat 
field, for example, will produce less g than one 
crashing into the side of a building. More 
immediate in pilot protection are shoulder 
straps and seat belts. With some give these 
may allow the pilot himself to decelerate within 
the cockpit. 
Since d is inversely proportional to g, 
doubling d will halve the g force. Thus, 
shoulder straps decelerating the pilot more than 
2" will allow him to take twice as much g 
force as would straps decelerating him in 1". 
Similarly, people falling into shrubbery or soft 
compressible dirt, by decelerating over a 
greater distance, can survive, uninjured, falls 
from greater heights than people landing on 
concrete, where d is practically zero, d may 
also be expressed as t or time of deceleration. 
The greater the distance, the greater the time. 
Protection may also be provided by altering 
the force distribution on the body. In crashes 
this is especially true. Since the g force is 
constant for a given velocity, it follows that 
the effective weight will also be constant. If 
the weight of the object can be supported over 
a greater area, the force per unit surface will 
be decreased. Thus a single force applied as 
pounds/sq. in. may be distributed over 50 sq. 
ins. as 1 pound/sq. in. More specifically, 
shoulder straps restraining a body with pos- 
sible fracturing of the clavicles can be replaced 
by a vest, where the impact is distributed 
throughout all the ribs with a resultant greater 
total force tolerance. In this respect forces 
up to 100 g have been sustained without 
serious injury during falls where the individual 
36 Chapter 3. —THE PROBLEM OF ACCELERATION 
landed flat on his back and thus distributed the 
force simultaneously over a large area of his 
body. 
Finally, protection may be obtained by dis- 
sipation of the force outside of the body. This 
may be done by the absorption of force during 
the collapse of structures in the airplane an- 
terior to the pilot, such as the propeller, engine, 
and the forepart of the cockpit. More directly, 
protection may be afforded by the inclusion of 
energy-absorbing materials in such wearing 
gear as crash-helmets. Crash helmets, in addi- 
tion, distribute the force from local areas to 
a greater portion of the head surface. Within 
the body, even, force may be absorbed by the 
compression of soft tissues or the bending of 
joints, with less damage than is sustained by 
those less energy-absorbing structures such as 
rigid bones. 
Thus it may be seen that the problems of 
linear acceleration in aviation are but an ex- 
tension of similar problems in civilian life. 
Of a more divergent nature are the problems 
of acceleration involving a change of direction, 
with or without changes of speed. For conven- 
ience these changes of direction have been 
termed radial accelerations, because the centri- 
petal force causing the acceleration may be 
measured fairly easily by its counterpart, 
my2 y2 
centrifugal force. Here F = —where 
K K 
equals the radial acceleration and R is the 
radius of the circle involved in the curved path. 
Such forces may be experienced in aviation 
during normal banking turns, in pulling out of 
dives, and in various aerobatic maneuvers such 
as spins and loops. As in linear acceleration, 
the force in terms of g can be calculated for 
a constant mass by merely dividing the ac- 
V2 
celeration of gravity or g = p. Although 
32.2 K 
in aviation V is usually hundreds of miles per 
hour and R is usually in thousands of feet, a 
reduction of both of these would give com- 
parable g forces. 
Such a reduction has been produced on a 
practical scale in the construction of Human 
Centrifuges. These machines, capable of up to 
100 r.p.m. and with radii of 20 feet, are thus 
able to simulate the radial acceleration forces 
found under most conditions of aircraft man- 
euvering. By accurate control of V and R, 
therefore, animals and humans may be in- 
tensely studied under laboratory conditions to 
determine the physiological effects of such 
forces and the safe limits to which the body 
may be so stressed. One such machine is at the 
School of Aviation Medicine and Research, Naval 
Air Station, Pensacola, Florida, (figure 3-1.) 
This type of force tends, at present, to have 
much lower g forces than the common injurious 
linear accelerations. Thus, the tearing of tis- 
sues and the fracturing of bones, common in 
crashes, are rarely encountered. The low forces 
of radial acceleration are, however, sustained 
for considerable lengths of time, often several 
seconds. Such a sustained force can result, 
eventually, in overcoming the inertia which 
tends to prevent certain nonfixed tissues and 
organs from altering their normal body rela- 
tionships. 
Of primary importance in this respect are 
the body fluids, blood, lymph, and cerebrospinal 
fluid. These fluids are normally contained in 
tubular structures which are seldom filled to 
capacity. The walls of the tubes, furthermore, 
are elastic and porous arid so may stretch and 
leak. Physiological balance is normally main- 
tained by an equilibrium of intra—and extra- 
vascular forces, a predominant factor of which 
is intravascular hydrostatic pressure. Within 
the blood vessels the internal hydrostatic pres- 
sure at any point is made up of two factors, 
residual pressure from the heartbeat and hy- 
drostatic pressure resulting from the weight 
of the column of fluid above the point. It is 
this last which is most altered by radial ac- 
celeration. Since effective weight is altered 
proportionally to g, this portion of the intra- 
vascular hydrostatic pressure at any point will 
vary as the multiple of the weight of the fluid 
column above it. For example, at 13 g the 
effective weight of blood or any water fluid 
will approximate that of mercury at 1 g. 
Perhaps the simplest consideration of the 
physiological effects on the fluid systems may 
be seen in the results following a change from 
the horizontal to the erect position. The im- 
mediate result of such a postural change is 
a pooling of blood in the dependent areas as 
the vessels there expand to hold more fluid. 
This pooling occurs on the venous side even 
37 AVIATION MEDICINE PRACTICE 
more than on the arterial side and results, 
consequently, in a decreased venous return to 
the heart. 
The cardiac output, therefore, falls and with 
it the arterial pressure in such sensitive areas 
as the carotid sinus and aortic arch. Reflexes 
are then initiated resulting in widespread vaso- 
constriction in areas below the heart. This 
tends to decrease the pooling tendencies and 
thus insures a more adequate return of blood 
to the heart. This is accomplished not so much 
by increasing the rate of flow through the 
lower areas but by decreasing the amount of 
blood that can descend and the average distance 
it can descend. Thus, less work is required to 
raise it back to heart level. Venous return is 
normally augmented by skeletal muscles acting 
as pumps on the venous system. In a quiet, 
erect individual the lack of the muscular pumps 
gradually allows pooling to occur in spite of any 
widespread vasoconstriction, so that blood pres- 
sure eventually falls and syncope, from cere- 
bral anoxia, may occur. But in the average in- 
dividual, under average conditions, the vasocon- 
striction and muscular activity supply the heart 
with a sufficient return of blood so that it can 
then pump an adequate supply against gravity 
the short distance upward to the head. 
This last follows, obviously, from the fact that 
in man the erect position is so well tolerated. 
Under radial acceleration, then, these 
changes are merely intensified. The greater 
effective weight of the blood produces a greater 
tendency to pool and a greater obstruction to 
Figure 3-1.—Human Centrifuge at the School of Aviation Medicine and Research, Pensacola, Florida, showing center 
column, revolving platform with observer's seat at the center and subject's seat at the end of the centrifuge arm. 
38 Chapter 3. —THE PROBLEM OF ACCELERATION 
venous return. In addition, raising the heavier 
blood to the head becomes a greater load on the 
heart even when adequate blood is present. It 
follows, then, that if the radial g is raised 
sufficiently high the reflexes involved will be- 
come inadequate. Pressure studies on the cen- 
trifuge have offered conclusive proof of this. 
Blood vessels below the heart, away from the 
center during centrifugation, have shown a 
linear increase in pressure directly proportional 
to g. Conversely, vessels above the heart have 
shown linear decreases in pressure directly pro- 
portional to g. Eventually, such a decreasing 
pressure in the head must reach a subfunctional 
level. 
Vision is the first sense to be distributed or 
to fail. Since the intraocular pressure is nor- 
mally about 28 mm. Hg, it is therefore to be 
expected that when the cranial blood pressure 
has fallen to this level the vessels supplying 
the retinae would be collapsed. Moreover, those 
vessels extending to the periphery of the ret- 
inae would be subject to intraocular pressure 
over a greater length and thus collapse more 
readily. Peripheral vision, therefore, should 
and does fail first. On the centrifuge (figure 
3-2) the subject has three lights to observe, a 
central one and two in the peripheral visual 
field. These lights are easily turned out by 
buttons under the right and left hand. If the 
lights are turned on at random intervals and 
if the subject is instructed to turn them off 
when seen, it is apparent that a 0-level can 
be reached where he leaves the peripheral 
Figure 3-2.—Close up of subject's seat on the Human Centrifuge. Note: 111 the conventional wheel-type of control with 
buttons at thumb level to turn out control panel lights; 121 control panel with 3 lights at eye level above the 
accelerometer; 131 Standard G-valve for suit pressure on railing at extreme left rear of subjet; (41 absence of 
foot pedals to eliminate tensing and bracing of legs; 151 miscellaneous wiring for the lead off of ECG, respiration 
(via thermocouple in the mouthl, ear opacity and ear pulse (via photo-cell unitl, suit pressures and acceleration. 
39 AVIATION MEDICINE PRACTICE 
lights on and still turns out the center lights. 
He is in a condition, then, of peripheral lights 
lost or PLL. At a slightly higher gf-level the 
central retinal arteries will collapse also and 
the subject will leave all of the lights on. His 
condition then is one of center light lost 
(CLL), or black-out {BO). At this point he 
still has an effective supply of blood to the rest 
of the brain, enhanced by a negative intra- 
cranial cavity spinal fluid pressure. 
It must be remembered that spinal fluid is 
also subjected to a dependent pooling force. But 
the rigid character of the cranial cavity pre- 
vents the general collapse of all intracranial 
vessels and spaces, so that fluid is maintained 
in these areas at pressures below atmospheric. 
This has been well demonstrated by movies of 
cranial vessels seen through watertight leucite 
windows in the skulls of monkeys subjected to 
such centrifuge studies. 
At black-out level the ringing of a bell, which 
the subject turns off in a manner similar to the 
lights, serves as further evidence that the sub- 
ject’s only failing is one of sight, that he still 
has adequate circulation for hearing, motor 
control, and consciousness in general. Higher 
gf-levels still will, obviously, eliminate even this 
last bit of circulation to the head. Unconscious- 
ness then ensues. The bell is left ringing, the 
hands drop from the wheel, and the head 
slumps forward on the chest. 
Ordinarily, experimental centrifuge runs on 
humans last from 10 to 15 seconds. This time 
interval is quite sufficient to establish the end- 
points desired, yet insufficient to cause perma- 
nent cerebral damage from temporary anoxia. 
Subjects who have had thousands of such 
centrifuge runs over a period of five years 
have spent “hours” blacked-out and “minutes” 
unconscious. They show no clinical evidence of 
any changes attributable to these experimental 
procedures. 
Since the essential stresses involved are of a 
nature of decreased venous return from the 
areas below the heart and of a decreased supply 
of blood to areas above the heart, it is under- 
standable that the duration of the g stress 
is important. Compensation for a low g force 
might and does fail when the force is sustained, 
while a higher g force may be well tolerated for 
a shorter time. Many people will faint on a 
tilt table when held quietly erect for twenty 
minutes. On the other hand, snap acrobatic 
maneuvers producing 8 to 10 g are well 
tolerated as the g is sustained for a second 
or less. The range for black-out threshold in 
average adult males during 15-second centri- 
fuge runs is 2.5 to 7.5 g, with the mean between 
U.O to U-5 g. 
One might ask how frequently are these 
levels approached in aircraft. Planes have 
recently crossed the continent averaging 600 
m.p.h. At this speed a turn with a radius 
of 2 miles would impose a centrifugal force 
of 9.5 g on the aircraft and all its occupants. 
Even a turn with 5-mile radius will produce 
3.5 g. Now this level frequently produces vis- 
ual dimming or PLL if maintained for approxi- 
mately 10 seconds. At 600 mph 15 seconds 
would be necessary to complete a 180° turn at 
this speed! 
Still other physiological changes of a cir- 
culatory nature may occur under radial ac- 
celeration, In the capillaries, for instance, the 
intra-extravascular fluid balance is maintained 
by four primary factors. Intravascular hydro- 
static pressure (HPV) and the collodial osmot- 
ic pressure of the tissues (COPt) act to move 
fluid outward. They are opposed by the hydro- 
static pressure of the tissue spaces (HPt) and 
the colloidal osmotic pressure of the blood, 
largely from plasma proteins (COPv). Nor- 
mally HP ranges from 35 mm. Hg. in the 
arterial end of the capillary to 15 mm. Hg. 
in the venous end. COPv remains fairly con- 
stant at about 25 mm. Hg. Under g, however, 
this balance is greatly upset by the transmis- 
sion of increased hydrostatic pressure from 
both arteries and veins to the capillary bed. 
The result is a greatly increased outward 
filtration of fluid and a consequent concentra- 
tion of the blood. By increasing the blood’s 
viscosity this concentration further impairs the 
venous return. Systemic (arterial) plasma pro- 
tein concentrations have shown increases of 
5 to 10 percent in young goats after only 30 
seconds of 5 g stresses. Such increased filtra- 
tion is also accompanied by extensive extra- 
vasations of plasma protein, which not only 
makes the 5 to 10 percent concentrations in- 
creases more significant but also decreases the 
ease of returning the fluid to the blood when 
40 Chapter 3. —THE PROBLEM OF ACCELERATION 
Figure 3-3.—The Standard U. S. Navy 1-2 anti-blackout suit partly inflated Inote abdomen). Note also the air source 
is attached by means of a quick disconnect on the left. Also pictured is a standard G-valve and oil Alter to 
demonstrate, statically, the method by wh’.ch the suit Alls under simulated G. This suit can be worn in place 
of the conventional coverall and is light weight and porous for skin ventilation. It may be worn under cold weather 
gear without discomfort or impairment. 
41 AVIATION MEDICINE PRACTICE 
the stress is terminated. Consequently, edema 
is a common finding in those body areas where 
tissue pressure cannot rise to counteract the 
filtration tendencies. This is characteristic of 
skin and mucous membranes, and more so of 
subcutaneous areas. In muscles, on the other 
hand, and similar tissues with inelastic and 
watertight membranes, a small extravasation 
of fluid produces a marked rise in tissue pres- 
sure, thereby restoring the vascular balance. 
This protects the involved vessels against 
further fluid loss or greater dilatation. 
The usual return of filtered fluid to the blood, 
especially when high in protein, is via the 
lymphatic system. These vessels, however, are 
subject to the same g forces, and flow in them 
is prevented by the same increase in hydro- 
static pressure as occurs in the arteries and 
veins. In particularly poorly protected blood 
vessels, or under higher g forces, the intra- 
vascular pressures may rise so much that they 
not only increase filtration and the loss of 
plasma protein, but they may even cause extra- 
vasation of formed blood elements, petechiae, 
and finally frank hemorrhage. Petechiae, for 
example, are frequently observed in humans 
after only 10 seconds at 6, 7 or 8 g. 
In addition to fluid readjustments under 
radial acceleration, both of a translocation 
within the vascular tree and a rebalance be- 
tween intra—and extravascular areas, other 
pertinent changes may be noted. These involve 
primarily an increase in the effective weight 
of some areas beyond the limits of the skeletal 
muscles involved to move them. Below black- 
out threshold there appears to be little impair- 
ment of hand, finger, and foot movement as 
regards operating controls efficiently. There 
is, however, a definite sensation of being pushed 
into the seat. At about 3 to 4 g raising the 
arms above the head and, more importantly, 
standing up from the seat (e.g., to escape 
from an uncontrolled aircraft), become quite 
difficult if not impossible. Finally, a few inci- 
dences of ruptured intervertebral discs have 
been reported following severe pull-outs from 
dives in aircraft. The in these cases, 
however, was undetermined. 
The means of protecting an individual 
against this type of force is therefore impor- 
tant. Several have been devised. The original 
clues toward the solution of this problem were 
obtained from pilots who learned, by trial and 
error, ways to diminish their black-outs. More 
recently centrifuge tests have demonstrated 
various factors affecting one’s black-out thres- 
hold. Tensing of muscles, especially of the ab- 
domen seemed to help the most; but it was also 
found that a full stomach, apprehension, and 
good physical condition also increased one’s 
g tolerance. The common denominator of these 
protections is fairly apparent. They aid the 
leg and abdominal blood vessels by either actual 
external pressure or by increasing vasocon- 
striction and blood pressure. They, therefore, 
act to prevent the dilatation of the vessels, 
pooling, and filtration. In addition, the in- 
creased pressure aids in supplying blood to the 
head. 
Such an understanding has led to the develop- 
ment of the present standard antiblackout suit. 
This suit is simply a tight-fitting garment with 
five air bladders (one over each calf, one over 
each thigh, and one over the abdomen) incor- 
porated in the cloth over those soft tissue areas 
most prone to allow pooling. The bladders are 
attached by means of a #-valve to operate 
automatically and fill with increasing pressure 
for increasing g. The principal of the valve is 
simply an application of Hooke’s Law that a 
spring will be stretched proportionately to the 
weight applied. Since the effect of g is to in- 
crease the weight, a plunger can be so attached 
to a spring that under 1 g it covers the air 
pressure inlet. Under increasing g the plunger 
then progressively uncovers more of the pres- 
sure inlet. As is removed, the inflow 
of air is again blocked and properly placed out- 
let valves can provide almost immediate release 
of the air pressure within the bladders. 
The standard valves in use are adjusted to 
activate at 1.75 g. Above this level they de- 
liver either 1 or 1.5 p.s.i. per g depending on 
whether the valve is set on low or high. The 
average protection so afforded is approximately 
0.7-1.0G for low and 1.0-1.5G for high. Not only 
does such a suit act to raise the pilot’s black-out 
level; but by its massaging action at sub-black- 
out levels it benefits venous and lymphatic re- 
turn and acts, thereby, as a significant anti- 
fatigue suit. 
As the importance of the height of the hydro- 
42 Chapter 3. —THE PROBLEM OF ACCELERATION 
Figure 3-4.—The Standard U. 5. Navy 1-3 anti-blackout suit. This is a cut down model of the 1-2 suit. It may be worn 
over the underwear and under or over conventional uniforms. It incorporates the air bladder systems of the 1-2 
in a form which can be worn with many other clothing arrangements. As pictured it is partly inflated. 
43 AVIATION MEDICINE PRACTICE 
static column was realized, another approach 
to the black-out problem developed. Venous re- 
turn could be aided by decreasing the vertical 
distance between the heart and the stressed 
area. Practically, this may be accomplished 
by raising the feet and knees, crouching or tilt- 
ing the seat backward. Crouching also was 
beneficial in decreasing the heart to head dis- 
tance although vision was then impaired. The 
limiting changes in this regard are, naturally, 
based on the assumption of a prone or supine 
position. These positions, while good hydro- 
statically, offer considerable difficulty in the 
operation of controls, introduce a problem of 
vision, and greatly increase the dangers during 
crashes. 
The problem of escape from uncontrolled and 
spinning aircraft is increased in high speed 
planes by acceleratory forces. As skeletal 
muscle capacity is surpassed, automatic es- 
cape mechanisms must be employed. The at- 
tack on this problem is of two forms. \ For 
intermediate velocity aircraft, ejection seats 
seem promising. In this manner seat and 
pilot under transient forces of 15 to 20 lin- 
ear g can be thrown clear of the aircraft. 
After reaching terminal velocity the pilot 
may then free himself from the seat or, with an 
appropriate parachute, ride the seat to the 
ground. 
For higher speed planes, wind blast, and 
tumbling (see below) seat ejection becomes un- 
satisfactory, Here a segment of the plane, a 
pod, or capsule containing pilot and seat must 
first be disengaged from the rest of the aircraft. 
The final solution has by no means been 
reached. 
Since radial g acts predominantly by pool- 
ing blood away from the center of curvature, 
it is evident that the gross position of the body 
can significantly alter the physiological effects 
produced. Radial g has, therefore, been sub- 
divided into various types depending on which 
area of the body is subjected to pooling. The 
position so far discussed wherein pooling is 
toward the abdomen and legs produces what 
has been termed positive radial g (+0). By 
the opposite criterion, positions which result 
in the pooling of blood toward the head end 
of the animal or man impose a force of nega- 
tive radial g(—g). There may also be trans- 
verse g, either prone with pooling anteriorly or 
supine with pooling toward the back. Finally 
there is lateral g with pooling from right to 
left or vice versa. 
From a circulatory standpoint the mechanics 
in each case are similar to those of -f g. Be- 
cause of the anatomical symmetry of the body, 
however, vastly different physiological disrup- 
tions may occur. The blood vessels stressed in 
negative g, for example, are normally subjected 
to little stress in an erect position. They are, 
therefore, less protected and more apt to suffer 
extensive filtration and hemorrhage. Thus it 
is that 30 seconds* of —3g can produce exten- 
sive edema in the soft tissues of the face, head, 
and neck of goats, profuse hemorrhages sub- 
mucosally in the larynx, mouth, nose, and 
sinuses and subconjunctivally in the eye. The 
larynx under —5g for 30 seconds can become 
Figure 3-5.—The Standard G-valve, at 1 G. Under this 
condition pressure from the left normally escapes 
through an exhaust at the lower right. As G lowers 
the central column on the spring, part of the pressure 
escapes via the upper right tube to the suit. After 
G is removed, this suit pressure then escapes via the 
small opening at the upper left which was closed 
during G. 
44 Chapter 3. —THE PROBLEM OF ACCELERATION 
se edematous and hemorrhagic that the airway 
is occluded and asphyxiation results. 
Intracranially, however, the cerebrospinal 
fluid protecting the blood vessels experiences 
the same hydrostatic pressure increases as do 
the blood vessels. Here, then, very little, if 
any, disruption of fluid balance occurs. Occas- 
sional hemorrhages which have been found 
within the cranium under negative g have 
been localized largely in the circle of Willis. 
They are attributed more to a tearing of the 
vessels which are stretched longitudinally, than 
to an increase of the intravascular pressure be- 
yond the limits of the vessels. The stretch is a 
result of the brain’s gravitation toward the 
upper part of the cranial cavity through the 
less dense cerebro-spinal fluid. 
As would be expected under negative g, the 
pressor reflexes are reversed. The increased 
pressures in areas such as the carotid sinus 
reflexly slow the heart, further aggravating 
the poor cerebral circulation. Humans at —Sg 
for 10 to 15 seconds have shown by ecg a 
bradycardia of 4 to 6 beats per minute. Rab- 
bits and goats at —5g have shown temporary 
cardiac arrest during 30-second centrifuge 
runs. Respiration is also markedly impaired 
under negative g. The increased effective 
weight of the abdomen is thrown onto the 
diaphragm making adequate inspiration that 
much more difficult. 
While in -\-g it seems possible to pool all 
the blood below the heart, under —g it appears 
that the cephalad loop of circulation cannot 
hold the entire blood volume. This results in a 
residual venous column of blood acting on the 
right heart. Enough pressure may be thus 
produced to precipitate cardiac failure in ex- 
perimental animals subjected to prolonged —g. 
This cardiac threat is also present under +g 
when anti-blackout protection is sufficient to 
prevent the pooling of all the blood below the 
heart. Consequently, this danger becomes a 
limiting factor in the amount of protection pos- 
sible or advisable. Negative g, through head 
and neck congestion, produces, in addition, 
marked discomfort which at levels above —3g 
approaches an unbearable intensity. Finally, 
there has been noted a certain mental confusion 
from this stress, for reasons at present not 
understood. 
In tumbling, an increasing problem follow- 
ing escape, be it by bailout, seat ejection, or 
capsule release, it is possible to produce high 
alternating positive and negative G. Upon 
leaving the aircraft the pilot becomes subjected 
to an extensive decelerative force which inten- 
sifies as the velocity of the aircraft is increased. 
As he tumbles, this force is directed alternately 
to opposite ends of his body. The forces in- 
volved, the physiological effects, and toleration 
limits are, as yet, unknown quantities. 
Transverse and lateral g, because the hydro- 
static columns are so small, do not produce 
circulatory difficulties which are critical. In 
these positions the limiting factor appears to 
be respiration. When the weight of the thoracic 
cage exceeds the ability of the intercostal and 
allied muscles to produce inspiration, effective 
respiration ceases. This limit averages 12 to 
14 g. 
Another form of acceleration of importance 
is angular acceleration. When the point of ro- 
tation is within the pilot, even small forces 
of g (under 2) may, by affecting the semicir- 
cular canals, initiate reflex eye movements. 
This produces a marked disorientation in the 
pilot and makes reliance upon instruments even 
more imperative, especially at night when ac- 
curate external visual orientation is impaired. 
THE PROBLEM OF VIBRATION 
Vibration, in a physical sense, has many of 
the attributes of acceleration. Reduced to sim- 
plicity it is a series of alternating linear ac- 
celerations with the greatest change in ac- 
celeration occurring at the end of each vibra- 
tory wave, when velocity is actually zero. The 
physiological effects, however, are not deter- 
mined, primarily, by the amount of accelera- 
tion, which is usually small, since the time in- 
terval is so short. Instead, the physiological 
changes are usually dependent upon the ampli- 
tude of the swing, measured in inches, and the 
frequency of these swings, measured as cycles 
per second (cps). 
If the logarithms of these two parameters are 
compared, the threshold for perception and the 
limit of human tolerance are essentially paral- 
lel. In the high amplitude ranges, both percep- 
tion and tolerance show an inverse linear re- 
lationship to frequency. The physiological sen- 
45 AVIATION MEDICINE PRACTICE 
sory receptors of vibration are quite diverse. 
Certain organs are stimulated by high ampli- 
tude, low frequency vibrations, while others 
respond to low amplitude, high frequency vi- 
brations. There is, however, considerable sen- 
sory overlap. 
One of the commonest forms of vibration 
is the high amplitude, low frequency form 
which produces motion sickness, well demon- 
strated in children’s swings and in the tossing 
of ships. In aircraft, air currents produce a 
similar effect termed air sickness. A major 
difference' in this form, however, is that the 
irregularity of the air currents make the vi- 
bration less regular. Such a gross vibration 
causes alternating mesenteric stretches and 
otolithic stimuli sufficient to account for the 
symptoms of which nausea is a predominant 
one. This discomfort has a lower threshold in 
the air than other forms of motion sickness 
because of the added effects of hypoxia (from 
altitude) and transient cerebral hypemias from 
the radial g of air maneuvers. Because of its 
irregularity, it is also associated with a buffet- 
ing character. By increasing the tendency to 
fatigue this aggravates the general discomfort 
of the individual. Myotactic stretch reflexes 
and skin vibratory sense organs may play a 
minor role. 
These sensory elements usually are more 
affected, however, by lower amplitude and 
higher frequency vibrations such as result 
from the engines and are transmitted through 
the body of the aircraft. When present they 
add in the development of a fatigue state. The 
subsonic vibratory range, with the exception 
of motion sickness, has so far yielded little 
evidence of significant physiological impair- 
ment. There is some suggestion that certain 
vibrations, transmitted to the body via skin 
and bone, may block the normal nerve trans- 
mission of vibratory sensations, primarily by 
stimulating the nerves for such transmission 
afferent to the sensory end organs. In general, 
however, much more research is necessary be- 
fore the final analysis can be made as to the 
physiological detriment of such vibrations. 
As the vibrations reach the sonic range the 
organ of Corti in the internal ear becomes the 
primary receptor of the body. The overlap of 
low sounds in auditory and tactile perception 
has been well established. It is this overlap in 
the low auditory frequency range which may 
play a prominent part in the production of the 
fatigue so characteristic of this type of vibra- 
tion. Loud sounds have a similar fatiguing 
effect and the auditory component in fatigue 
may possibly be more important than the tactile 
vibratory one. 
In the audible vibratory range the amplitude 
of vibration, which is measured predominantly 
as decibels, becomes the limiting tolerance fac- 
tor. Discomfort at about 120 decibels (lx 102 
— lx 106 inches) becomes unbearable and 
takes a form of intense pain in the ears, prob- 
ably from the extensive vibration of the sound 
conducting organs, ear drum, ossicles, and 
endolymphatic fluid. Hemorrhages have been 
found in these areas following painfully loud 
noises. At levels of noise loudness only slightly 
below tolerance limits, temporary deafness may 
result from prolonged exposure. In some cases 
this deafness may become permanent, especially 
in the higher frequency ranges. Extraneous 
noise has one further detrimental characteristic 
for the aviator: it interferes with communica- 
tions and thereby decreases the safety of both 
the pilot and the plane. 
The part of suprasonic vibrations in the phy- 
siological picture is still poorly understood. 
Data so far available is largely of a spotted 
nature over the amplitude vs. cps. tolerance 
curve. The following examples serve as indi- 
cations of the known dangers of such vibra- 
tions : 
1. 10,000 cps. of 1 x 102 in. amplitude kill 
isolated cells, 
2. 300,000 cps. of 1 x 105 in. amplitude 
rupture cellular organisms and fragment their 
cellular components, kill small fish and frogs, 
temporarily immobilize mice but do not affect 
bacteria. 
3. 340,000 cps. of 1 x 105 in amplitude 
produce cardiac rhythm abnormalities in frogs 
and turtles. 
4. 835,000 cps. of unmeasurable but minute 
amplitudes cause varying vulnerability of nerve 
tissue cells and bizarre neurological lesions in 
cats, dogs, and monkeys. 
Consequently, the effect of jet and allied en- 
gines with suprasonic vibratory frequencies up- 
on the human body can at present only be 
46 Chapter 3. —THE PROBLEM OF ACCELERATION 
hypothecated. No detrimental effects in humans 
have been attributed unimpeachably to these 
vibrations up to the present time, but this may 
well be simply a result of inadequate testing 
procedures. 
The attack on the problem of vibration is 
likewise incomplete. Various dampening ma- 
terials can be incorporated to decrease the 
amplitude of many vibrations, especially in 
the noise range. Within the cockpit, the pilot 
appears fairly well protected, also—by mater- 
ials capable of attenuating high frequency, low 
amplitude vibrations—from the high-speed en- 
gines. The greatest possible danger in this field 
appears to be to the maintenance crew outside 
the plane, subject as it is to the vibrations in 
the air currents from the exhaust tubes. 
THE PROBLEM OF FATIGUE 
Fatigue as an entity is the sum total of 
factors, both physiological and psychological, 
tending to decrease the work performance of 
the individual as a result of previous work. In 
general, these factors have been discussed at 
length under their various headings, as fatigue 
is only one of their effects. It seems desirable 
at this point, however, to list these factors 
briefly as regards the particular part they 
play in the fatigue picture. 
Prolonged muscular exertion has long been 
recognized as a primary factor in fatigue. 
Muscular work by aviators is often extensive 
although a great amount of it may be relatively 
unconscious. The ever present threat of injury 
and death produces a mental apprehension, sub- 
conscious or not, which is reflected in a state 
of constant increased muscular tenseness. This 
tenseness is increased consciously during man- 
euvers and unconsciously during travel through 
rough air, which requires the continuous brac- 
ing of the body to counteract the buffeting of 
the airplane. When the pilot is cold, shivering 
is superimposed on all the other muscular work. 
Since the combat of such fatigue is largely 
a circulatory and respiratory problem of sup- 
plying oxygen to the working tissues, anything 
impairing this supply will increase the fatigue. 
Anoxia from reduced barometric pressure, es- 
pecially in a chronic low-grade form, may be- 
come quite significant at altitudes where oxy- 
gen equipment is not utilized. Radial accelera- 
tion during flights involving extensive ma- 
neuvers may produce many periods of de- 
creased cranial circulation. More important, 
from the fatigue standpoint, is the decreased 
circulatory efficiency from the repeated in- 
creased filtration in the stressed capillaries of 
the legs and abdomen. For both situations, how- 
ever, the antiblackout suit has proved quite 
efficient as an antifatigue suit. 
Others factors act to produce fatigue by de- 
creasing the body reserves. Dehydration from 
excessive sweating during prolonged flights in 
the tropics, or during exposure to excessive 
radiant heat, is an example of this type. Hunger 
from missions requiring many hours in the air 
is another. These may best be combatted by 
adequate stores of food, drink, and salts in 
the aircraft to replenish the pilot as they are 
needed. Proper cockpit ventilation will also 
aid against excessive temperatures and humid- 
ity. 
Beside the definite physiological factors pres- 
ent, several psychological factors may develop. 
Situations involving discomfort may more truly 
involve both. These include buffeting, cold, 
heat, hunger, eyestrain (from poor lighting, 
glare, etc.), poor fitting and uncomfortable 
clothing and equipment, noise, and vibration. 
More psychological but still a form of discom- 
fort, although mental, is the constant threat 
of death and injury, a factor which during com- 
bat missions, especially, may become quite pro- 
nounced and lead to the symptom complex of 
aviator’s fatigue, a form of combat or war 
fatigue. 
Boredom is a most critical factor in the pro- 
duction of mental fatigue. This was well il- 
lustrated by the wartime greater incidence of 
fatigue on the return trips from combat mis- 
sion, At this time the pilot and crew were no 
longer keyed-up in anticipation of the coming 
fight or danger. This fatigue type may be 
combatted to a slight degree by many minor 
actions, such as eating an apple or candy bar, 
dripking fruit juice, or singing. More phar- 
macologically it can be dealt with by such 
drugs as caffeine (hot coffee) and benzedrine, 
which have the capacity to stimulate the corti- 
cal cells of the brain and reduce the sensations 
of fatigue. 
47 AVIATION MEDICINE PRACTICE 
The sum total of the means of combatting 
fatigue are, however, in the last analysis, 
merely the application of all the means of 
combatting the various factors leading to the 
production of fatigue. Since physiological re- 
serve is so important, it is in this field that 
health, conditioning, and training have some 
of their greatest practical applications in avia- 
tion. 
QUESTIONS 
The following review questions should be helpful in 
connection with the preceding text: 
1. What are the physical differences between linear 
and radial acceleration ? Give common examples of each 
in aviation. 
2. What are the force vs time relationships com- 
monly seen in linear acceleration ? In radial accelera- 
tion ? 
3. Explain the fundamental differences in the effects 
on the human body of linear acceleration as compared 
to radial acceleration. 
4. Explain blackout. 
5. Describe the physiological forces involved in pool- 
ing and filtration of blood under radial acceleration. 
6. Explain the difference in circulatory and respira- 
tory physiology of positive and negative radial accelera- 
tion. 
7. What determines the physiological limit of linear 
acceleration ? Of positive, negative, and transverse 
radial acceleration ? 
8. Explain the difference in physiological effects of 
negative radial acceleration upon the face and the con- 
tents of the cranial cavity. 
9. What are the protective devices used against 
acceleration and how do they afford protection ? 
10. What are the sensory receptors for vibration and 
over what vibratory ranges of amplitude and frequency 
are they sensitive ? 
11. What are the detrimental physiological effects of 
vibration ? 
12. What protection is possible against vibration ? 
13. What factors contribute to the state of fatigue 
of an aviator? 
14. What are the means of avoiding or diminishing 
the fatigue of aviators? 
BIBLIOGRAPHY 
1. H. G. Armstrong, Principles and Practice of Avia- 
tion Medicine, 2nd Ed., The Williams and Wilkins Co. 
(Baltimore, 1943). 
2. Britton, S. W., E. L. Corey and G. S. Stewart, 
Effects of high acceleratory forces and their alleviation. 
Am. J. Physiol. 146:33-51 (1946). 
3. Britton, S. W., V. A. Pertzoff, C. R. French and 
R. F. Kline, Circulatory and cerebral changes and pro- 
tective aids during exposure to acceleratory forces. Am. 
J. Physiol. 150:7-26 (1947). 
4. Burt, A. S., Annotated bibliography on the phys- 
iological effects of acceleration in aircraft. School of 
Aviation Medicine, U. S. Naval Air Station, Pensacola, 
Florida, 1945. 
5. Gamble, J. L., R. S. Shaw, 0. Gauer and J. P. 
Henry, Physiological changes during negative accelera- 
tion. U.S.A.F., Air Material Command, Dayton, Ohio, 
MCREXD 695-74L, 25 July 1948. 
6. G Sense, Office of the Chief of Naval Operations, 
U. S. Navy, December, 1943. 
7. Ham, G. C., Effects of centrifugal acceleration on 
living organisms. War Medicine 3: 30-56 (1943). 
8. S. Lippert, Comprehensive graph for the collec- 
tion of noise and vibration data. J. Am. Med. 19:279- 
286, 1948. 
9. Lombard, C. F., How much force can the body 
withstand? Aviation Week 50:20 (1948), 
10. R. A. McFarland, Human Factors in Air Trans- 
port Design, McGraw-Hill Book Company, Inc. (New 
York, 1946). 
11. P. M. Morse, Vibration and Sound, 2nd Ed., 
McGraw-Hill Book Company, Inc. (New York, 1948). 
12. Orientation, School of Aviation Medicine and 
Research, U. S. Naval Air Station, Pensacola, Florida, 
1947. 
13. Physiology of Flight, AAF Manual No. 25-2, 
Headquarters, AAF, Washington, D. C., 15 March 1945. 
14. Rushmer, R. F., E. L. Beckman and D. Lee, 
Protection of the cerebral circulation by the cerebro- 
spinal fluid under the influence of radial acceleration. 
Am. J. Physiol. 151:355-365 (1947). 
15. Anti-Blackorit Suits, Aviation Training Division, 
Office of the Chief of Naval Operations, U. S. Navy, 
NavAer 00-80V-67. 
16. C. J. Wiggers, Aviation Physiology, chapters 28- 
29, Physiology in Health and Disease, Uth Ed., Lea and 
Febiger (Philadelphia, 1944). 
17. Wood, E. H., E. H. Lambert, E. J. Baldes and 
C. F. Code, Effects of acceleration in relation to avia- 
tion. Federation Proc., 5:327-344 (1946). 
48 CHAPTER 4 
OPHTHALMOLOGY IN AVIATION MEDICINE * 
Editor’s Note.—Recent changes in the Manual of the Medical 
Department have not been included in this chapter. Other changes 
will be made from time to time. Reference should always be 
made to a currently corrected copy of the Manual of the Medical 
Department, U. S. Navy for existing physical standards and pro- 
cedures. 
INTRODUCTION 
Probably the most important function of the 
flight surgeon, as far as ophthalmology is con- 
cerned, is the conduction of that portion of the 
flight physical examination related to the eyes. 
It is essential that any pathology be detected 
which might interfere with the proper per- 
formance of flight. It is also desirable to pre- 
dict any condition which might become worse. 
It is undesirable both from the point of view 
of the Government and of the individual for a 
candidate to spend many months in expensive 
training only to find that he has developed a 
defect which will preclude his designation as 
a naval aviator. The technique of the flight 
physical examination will therefore be dis- 
cussed. We will also endeavor to explain why 
certain physical standards are set for the quali- 
fication of the candidate for flight training. 
It is quite obvious, even to medical students, 
that the more profound the knowledge of anat- 
omy and physiology, the more interesting and 
understandable becomes the pathology. The 
limitations of time and space will permit only a 
brief discussion of these basic sciences. The 
reader is urged, if time is available, to scan 
through The Anatomy of the Eye and Orbit 
by Wolff and to study the excellent anatomical 
transparencies presented in McHugh. The dis- 
cussion on muscles will be much more inter- 
esting if you have the anatomy well in mind. 
Of course a good flight surgeon will be able 
to offer the maximum amount of clinical care 
in regard to common complaints, which are no 
different in aviators than other people. The 
more problems the flight surgeon can handle 
within his own squadron the more confidence 
he will share with his airmen. The daily visits 
involved in handling minor complaints gives 
the flight surgeon close and invaluable con- 
tact with the personnel of his squadron. 
“Diseases of the Eye” by May, has a wealth 
of material packed into not too many pages. 
The author is a master of word efficiency. You 
probably have read it in your medical school 
days. Try to read it again—even the fine print 
on anatomy and physiology at the beginning of 
each chapter. It will help you understand how 
to handle minor eye conditions and make you 
confident as to when to call for assistance. 
The experienced medical officer knows when a 
consultation is desirable and should never hesi- 
tate to call for one if circumstances so indicate. 
Such measures will not destroy the confidence 
of your squadron in your professional ability. 
Your efforts will be conducive to gaining con- 
fidence and good will. 
VISUAL ACUITY 
An accurate testing of visual acuity is more 
valuable than any other single test in the ex- 
amination of the eye. We all consider that 
20/20 means vision is normal. That is gener- 
ally true but why do some people read 20/15? 
Failure in visual acuity is the most common 
cause for failure of flight physical exams. The 
subject is worthy of considerable thought. 
To take visual acuity a patient is placed pref- 
erably 20 feet from a group of test letters. 
The smallest letters read correctly, without 
hesitation, indicates the visual acuity. A few 
letters missed on a line may be ignored if the 
* Prepared by John T. Smith, Capt. (MC) USN and George W. 
Rand (MSC) USN. 
49 AVIATION MEDICINE PRACTICE 
candidate reads an equal number of letters cor- 
rectly on the next smallest line. Visual acuity 
is recorded as a fraction but it is not really 
10 , • , • i ... 20 
a fraction. which is also written as 
is not 50 percent of normal vision; it is 80 per- 
the range of physiological nystagmoid move- 
ment for a given individual. This complicated 
physiological phenomena can be summarized in 
a single statement for the normal eye: when 
the visual lines of any two points make an 
angle of 1 minute or more at the nodal point of 
the eye they are distinguished as two points on 
the retina, (figure 4-1.) 
Figure 4-1.—The greater the distance from the nodal 
point the farther apart must two points be to sub- 
tend a 1 minute angle at the nodal point. INI 
cent of normal vision. The recording of visual 
acuity is nothing but a shorthand way of say- 
ing, “The person was placed 20 feet from the 
vision chart and read only the size letter that 
a normal person could read at 20 feet.” 
Distance of patient from letters. 
Distance for normal eye for the size letter used. 
The manner in which these letters are pre- 
pared is of interest in understanding the physi- 
ology of vision. 
One essential factor in normal visual acuity 
is the resolving power of the retina. Funda- 
mentally, the resolving power of a retina is the 
ability to distinguish two points as such at a 
given distance. To accomplish this the image of 
each point must fall on the retina in such a 
manner as to be separated by at least the width 
of a single cone cell ending. This ability de- 
pends upon several factors, only two of which 
are the actual width of a person’s cones and 
Figure 4-3.—Each letter subtends a S' angle at the nodal 
point INI. Each point of separation of the letter 
subtends a T angle. 
For the preparation of test letters the amount 
of separation of two points whose visual lines 
subtend a 5' angle at the nodal point is fig- 
ured for any particular test distance. A square 
is outlined using this measurement as any one 
side. The square is then subdivided into 25 
smaller squares. These smaller squares are used 
as a guide in the preparation of test letters. It 
is obvious that such letters will possess por- 
tions that subtend a 1' angle on the retina and 
the separation must be recognized in disting- 
uishing the characteristics of any particular let- 
ter. (figure 4-3.) 
The most common method of recording vision 
in the United States is the Snellen system 
which entails a vision test card which has let- 
ters of various sizes. Each letter, however, has 
distinguishing separation spaces which sub- 
tend the 1' angle for the particular distance 
which the letter represents; that is, 200 feet, 
100 feet, 70 feet, 60 feet, etc., down to 10 feet. 
(The patient remains at 20-foot distance 
throughout the test.) The other system, called 
the Grow system, used on Navy forms for many 
years, entails a card which bears many lines of 
letters, all the same size, and of such size that 
the distinguishing separation spaces subtend 
the 1' angle for 20 feet. In using this type card, 
the patient must be moved closer or farther 
from the chart to obtain a recording. 
Figure 4-2.—The entire box subtends a S' angle for any 
distance. Each small box subtends a V angle. 
50 Chapter 4. — OPHTHALMOLOGY IN AVIATION MEDICINE 
Figure 4-4.—Myopic eye or long eye at rest, focuses dis- 
tant objects in front of the retina. 
Figure 4-5.—The hyperopic eye or short eye. At rest, 
distant objects come to a focus behind the retina. 
The Snellen system entails keeping the pa- 
tient at a constant 20 feet throughout the test 
and changing the size of the letters. The Grow 
system entails keeping the size of the letters 
constant and changing the distance of the pa- 
tient. Visual acuity, therefore, is a shorthand 
expression which is written like a fraction. 
Numerator Distance of patient 
Denominator Size of letters. 
The faculty of normal resolving power is only 
one factor necessary for normal visual acuity. 
Resolving power is of no avail if the eye is so 
defective in focusing as to produce a blurred 
image on the retina. A profound discussion of 
the subject of refraction is beyond the scope 
of this paper. The flight surgeon should know 
that myopia is the most common reason for 
failure of a candidate to pass the original ex- 
amination for flight training. Myopia also takes 
its toll of candidates during flight training. 
Astigmatism is also a bugaboo for candidates. 
However, astigmatism is not usually progres- 
sive. Once a candidate enters the training pro- 
gram astigmatism seldom is a cause for dis- 
qualification. 
Most cases of myopia are caused by the fact 
that the eye is too long for its refractive power. 
At complete rest such an eye would focus a 
distant object (test letters at 20 feet) in front 
of the retina, (figure 4-4). No amount of effort 
can change this situation for what is needed 
is not effort but relaxation. This individual is 
trying to relax his ciliary muscle and make his 
lens flatten out more. He is trying to drop the 
image back to the retina. Candidates for avia- 
tion often fall into the hands of charlatans who 
claim they can train a myope to read normally. 
It is true that many honest scientists are try- 
ing experiments which they hope might cause 
the myope to flatten out his lens at rest. But 
so far all these experiments have failed. None 
of these honest workers make any promise to 
cure myopia or to “get the candidate by the 
exam.” 
But the reader may say to himself “I hap- 
pen to know of a fellow who failed his examina- 
tion because of myopia and then took this or 
that training and exercise and then passed the 
examination.” It is not possible to go into de- 
tail here about such cases. However, all these 
stories, if fully investigated, prove false. To 
the present date no cure for myopia is known. 
Correction by glasses or contact lenses—yes! 
However, it has not proven economical to the 
present writing, to invest $75,000 in training a 
candidate who needs glasses or contact lenses 
to see clearly. 
All babies are born hyperopic or far-sighted. 
Their eyes are too short to focus even a distant 
image on the retina. When the lens is com- 
pletely relaxed a distant image is focused be- 
hind the retina, (figure 4-5.) They see clearly 
only by accommodating the lens. 
As the child grows, his eye grows longer. If 
the growth stops short (hyperopia) or at just 
the right length (emmetropia) the individual 
goes on through life able to see clearly for 
distance, provided, of course, that his resolving 
power is normal. If the eyeballs grow too long 
they become myopic. This occurs early in some 
individuals. Most myopias however, become 
manifest between the ages of 16 and 23 years. 
This is the age when candidates present them- 
selves for flight training. Often candidates slip 
through the aviation physical examination and 
start their training. The lengthening of the eye 
ball continues. Too many candidates who start 
flight training fail to complete their training 
because the final lengthening of the eye ball 
occurs while they are still in training. Since 
almost 20 percent of Americans become myopic 
51 AVIATION MEDICINE PRACTICE 
by the age of 23, this defect is a very great 
problem in the selection of candidates for fly- 
ing. We could avoid this loss if we permitted 
only moderate hyperopes to start training. This, 
however, would so limit our field of selection 
that many fine candidates would be lost. Up 
to the present time it has been deemed im- 
practical to so limit the field of selection. 
But there is a long range reason for limita- 
tions even among hyperopes. The modern avi- 
ator does much of his flying by instruments. He 
must read charts and navigate. All this requires 
close work, Hyperopes fail in close work much 
earlier in life than emmetropes. The higher the 
hyperopia the earlier the failure. An aviator 
who requires bifocal lenses is not qualified for 
unrestricted flying. Therefore, a high hyperope 
might have 5 years cut off his period of use- 
fulness as an unrestricted flyer. 
The true refractive nature of an eye can only 
be determined by doing a cycloplegic refraction. 
All fully qualified flight surgeons are able to do 
this type of examination. 
For the many medical officers who cannot re- 
fract, but who must conduct preliminary physi- 
cal exams at isolated or distant ships or sta- 
tions, a careful visual acuity test must take 
the place of a cycloplegic refraction. 
The task of taking visual acuity should not be 
delegated to persons of doubtful ability or re- 
liability. The instructions in the Manual of the 
Medical Department are important enough to 
justify summarization here: 
1. Use standard Snellen letters provided by 
any reliable manufacturer. 
2. Have patient seated 20 feet from chart. 
3. Provide equivalent of a 200-watt light 
thrown on the chart from 4 feet distance. 
4. Do not give the candidate a chance to 
memorize your eye charts. Change them fre- 
quently. 
5. Test the right eye first. 
6. Reading without hesitation means read- 
ing the 10 letters in 5 seconds. 
Medical officers will spare candidates severe 
disappointment if they will arrange for a cyclo- 
plegic refraction of all candidates who have 
doubtful visual acuity. Candidates for flight 
training must read 20/20 without mistake or 
hesitation. 
It would be wise, if there is the slightest hesi- 
tation in reading 20/20 for the medical officer 
to put a plus 0.25 dropter sphere in front of the 
candidate’s eye. If this blurs the 20/20 line, a 
refraction under cycloplegic should be done if at 
all possible. 
Once a flyer has his wings he is allowed to 
continue unlimited flying as long as his visual 
acuity is 15/20 or better, unaided by glasses. 
This is not an inconsistent standard. We want 
to induct into training only candidates whose 
vision is excellent. Once an aviator is fully 
trained and experienced he is able to compen- 
sate for a slight loss of visual efficiency. 
For those who are familiar with the cyclo- 
plegic refraction—the acceptable limits of re- 
fractive error are as follows: 
1. Not more than 0.50 diopter of myopia in 
any meridian. 
2. Not more than 0.50 diopter of astigmatism 
in any meridian. 
3. Not more than 2.00 diopters of hyperopia 
in any meridian. 
In conclusion, a test of visual acuity is truly 
a test of a complicated mechanism. If we as- 
sume that the optic tracts and radiations are 
all normal, the visual acuity is determined by: 
1. Resolving power. 
2. Ability to focus an image clearly. 
3. The clarity of the media of the eye. 
The term 20/15 indicates better than average 
vision. It is useful to refractionists who wish, 
of course, to correct refractive errors in such 
a way as to provide the patient with the best 
vision that his visual system is capable of at- 
taining. To the flight surgeon, it has little 
known significance. Perhaps someone should 
run a series of tests comparing the capabilities 
of aviators who have 20/15 vision with those 
who have a mere 20/20 vision. 
There are several possibilities to explain 
20/15 vision. They are listed as follows: 
1. The persons cone cells are smaller. 
2. The persons media are clearer. 
3. The persons psychological processes are 
sharper. 
It is generally accepted that the rare cases 
of apparent improvement obtained from visual 
training courses to improve visual acuity are 
52 Chapter 4. — OPHTHALMOLOGY IN AVIATION MEDICINE 
attributed to the third factor. The individual 
gazes at test letters daily until he has learned 
that a certain type blurr on his retina is an 
“E,” another is “H.” The best results of this 
type training are attained with persons whose 
vision is very low; (i.e. 20/100 to 20/60) and 
whose intelligence and power of observation is 
very high. It is rare to raise a patient from 
20/25 to 20/20. Even if this is accomplished 
and the candidate “slips through” the flight 
physical, he will never complete the training 
program. The very myopia which caused the 
need for training exercises will increase dur- 
ing training. It is estimated that 98 percent of 
those persons who “jam” their way into flight 
training by such methods become more myopic 
during the training course and at some time 
or other must be dropped from the program. 
Test visual acuity carefully: 
REVIEW QUESTIONS 
20 
1. What does the expression — mean when written 
out in full ? 
15 
2. What does mean when written out in full ? 
3. About how much loss of visual efficiency does 
20/40 indicate? 
4. What is the normal minimum visual angle? 
5. Where does the image of a distant object fall in 
relation to the retina of a myopic eye? 
6. What can a myope do, through his own effort, to 
improve his distant vision? 
7. What is the most common cause for failure to 
pass the visual acuity test for flight training? 
8. At what age does myopia usually stop its progres- 
sion ? Give a reason. 
9. Why is a high hyperope undesirable in aviation ? 
10. What factor or condition of the eyeball itself can 
cause lowered visual acuity? 
ACCOMMODATION 
Accommodation should be an interesting sub- 
ject to all Americans for eight out of every ten, 
if they live long enough, will some day be em- 
barrassed by the inadequacy of their accom- 
modative power. 
When a person who sees clearly in the dis- 
tance (reads 20/20 on the eye chart) shifts his 
gaze to some near object, a momentary blur oc- 
curs due to the fact that the image of the ob- 
ject looked upon falls behind the retina. This 
momentary blur sets up a stimulus which causes 
the ciliary muscle to contract and the focus is 
brought forward just enough to put the image 
on the retina. 
It is obvious that the myope with long eyes 
requires less dioptic power to accomplish this 
focus of near objects than the emmetrope. The 
hyperope, on the other hand, needs much more 
power than the emmetrope. 
Let us set aside the many theories for ex- 
plaining accommodation and accept the fact that 
an increase in needed dioptic power is accom- 
plished by contraction of the ciliary muscle and 
a resulting bulging of the crystaline lens. 
Furthermore, the amount of dioptic power 
which a person is able to produce by contraction 
of the ciliary muscle is fairly uniform for nor- 
mal eyes of a given age. This is true regardless 
of whether an individual is a myope, emmetrope 
or hyperope. It is also accepted that the ability 
to produce such dioptic power decreases with 
age. Persons may succeed by fair means or foul 
to hold back the effects of age on their out- 
ward appearance but the loss of accommodation 
which accompanies age is normally as certain 
as the daily rise of the sun. 
Accommodative power is determined by em- 
ploying a card which bears the smallest size 
print that the patient is capable of reading. 
The card is held very close to the eye and slowly 
moved away until the patient is just able to 
read. The distance of this point from the eye 
permits, by calculation, an expression of the 
dioptic power produced. 
Dioptic power is the reciprocal of the focal 
length expressed in meters. If a person with 
no refractive error (an emmetrope) reads very 
fine print at 10 cm. it is assumed that his own 
lens has bulged sufficiently to produce the same 
effect as a lens of 10 cm. focal length. Since 
10 cm. is 1/10 meter, the power of lens neces- 
sary in this case would be the reciprocal of 
1/10 or 10 diopters. 
A special rule called the Prince rule is pro- 
vided for aviation physical exams. The calcula- 
tion has been done by the manufacturer and 
the examiner can read off his finding in terms 
of diopters. The tip of the rule is placed 11.5 
mm. in front of the cornea. A card of fine print 
is placed close to the eye and gradually moved 
away until the print is legible. 
53 AVIATION MEDICINE PRACTICE 
A reading which is much lower than the 
average for the age of the particular person is 
due to: 
1. A very high hyperopia (over 2 diopters). 
2. The presence of pathology such as irido- 
cyclitis, glaucoma, diabetes, or toxemias. 
3. Paralyzing drugs such as homatropine 
which might have been used by a candidate 
bluffing his way past the examination. (It flat- 
tens the lens and often improves a myopic con- 
dition.) 
Any of these situations would be undesirable 
in a naval aviator. With this in mind the stand- 
ards for qualifications require that the accom- 
modation reading for each eye must be within 
3 diopters of the average for the age of the 
examinee. 
The following is a table of average accommo- 
dation at various ages. 
5. If a person 18 years old was hyperopic to the 
extent of 1 dioptic, how much accommodation should 
be shown on a test rule ? 
6. If a 45-year-old person is myopic to the extent 
of 3 diopters, how much accommodation should be shown 
on a test rule ? 
7. How much accommodation is required for a per- 
son to be qualified for flight training? 
8. Why is adequate accommodation necessary for an 
aviator ? 
9. Name a few causes of inadequate accommodation. 
10. How much accommodation must an emmetrope 
produce in his lens system in order to read clearly at 
33-1/3 cm.? 
PHORIAS AND THE PHOROMETER 
When a person fixes his eyes on an object or 
changes his gaze from one object to another 
a series of rapid events occur. One eye becomes 
the fixing eye. (This fixing eye is usually con- 
stant for most people. A small percentage of 
persons alternate the eye which is chosen for 
the fix.) As soon as the assigned eye fixes, 
it has taken such a position as to put the 
macula, the nodal point of that eye, and the 
object fixed upon, in one line. The other eye, 
unless it by chance is already fixed, receives 
the image of the object on a part of the retina 
off the macula. The result is either blurred vi- 
sion or a momentary diplopia. Either one of 
these conditions causes a stimulation of the 
fusion center with a resulting motor response 
to shift the nonfixing eye so that it too has 
the object, the nodal point and the macula in 
line. 
These events occur so rapidly that neither 
the person fixing or an observer can readily 
detect the movement. That portion of the brain 
which reacts to the stimulus of blurring or 
diplopia is called the fusion center. Physiolo- 
gists do not know where it is located, but 
the facts indicate that such a center exists. 
When the fix has once been accomplished it 
is held by the normal human as long as he 
desires. Some eyes have a neuromuscular bal- 
ance which might be compared to a well bal- 
anced window and sash weight—the fix re- 
mains, by muscular balance, with little effort. 
Such a person is said to be orthophoric or 
demonstrates orthophoria. The eyes of most 
individuals, however, have a tendency to turn 
or drift up, down, in, or out. This tendency to 
drift is usually due to over tonicity of one or 
Age 
Diopters 
Age 
Diopters 
18 
11.9 
25 
10.2 
19 
11.7 
30 
8.9 
20 
11.5 
35 
7.3 
21 
11.2 
40 
5.9 
22 
10.9 
45 
3.7 
23 
10.6 
50 
2.0 
24 
10.4 
70 
0.5 
Most people must bring average newspaper 
print to 33 cm. from the eye in order to read 
the print clearly. This means the eye must de- 
velop 3 diopters of accommodation over and 
above their distant correction. A glance at the 
table will make it obvious that somewhere be- 
tween 45 and 50 years of age 3 diopters can 
no longer be produced and in most cases glasses 
must be worn for reading clearly. This stage, 
at which reading glasses are needed, comes 
on much earlier for hyperopes and later for 
myopes. 
REVIEW QUESTIONS 
1. Briefly, how is accommodation accomplished in 
the human eye ? 
2. What is the total dioptic power of accommodation 
which the average 18-year-old eye is able to produce? 
3. What is the total dioptic power of accommodation 
which the average 45-year-old eye is able to produce? 
4. In testing accommodation, do you move the card 
toward the eye or away from it? 
54 Chapter 4. — OPHTHALMOLOGY IN AVIATION MEDICINE 
two muscles or undertonicity of their antogo- 
nists. Although this tendency to drift is present 
in most people, the actual drifting seldom takes 
place. This is explained by the constant balanc- 
ing neuromuscular effort which is stimulated 
by the fusion center. 
Phoria, therefore, is defined as a tendency 
of the eyes to drift off from a fixed object, 
which tendency is fully compensated and, there- 
fore, is only detected by the use of a special 
diagnostic technique. 
It is logical to assume that a person who 
has a tendency to drift, and who maintains for 
long hours a compensating muscle stimulus so 
as to prevent the actual occurrence of drifting, 
will eventually tire. The result will be either a 
breakdown of the fix and a resulting diplopia 
or a psychic strain which will manifest itself 
as headache, vagus discomfort, and a loss of 
efficiency. The degree of discomfort and the 
rapidity of its onset depends on the degree of 
phoria. It is obvious that in seeking candidates 
for aviation certain limits of phoria must be 
avoided. For this reason the flight surgeon 
must acquire the technique and understand 
the use of the phorometer. This instrument is 
generally accepted as the most efficient and ac- 
curate means of measuring phoria. 
Esophoria is the tendency of the eyes to 
turn in. It is due to overaction of the internal 
rectus muscles or underaction of the external 
rectus muscles. That statement does not help 
us much, for it is obvious. The big question 
is why do these muscles overact or underact? 
The answer to that is a little beyond our scope. 
However, here are a few possibilities: 
1. A young man is astigmatic and goes 
through high school not knowing that he needs 
corrective lenses. During his long hours of 
study he brings the book closer to his eyes so 
as to make the blurring caused by astigmatism 
less annoying. This calls for constant converg- 
ence and a resulting increase in strength of the 
internal rectus muscles. He, therefore, may de- 
velop an esophoria for distance. The same 
young man, when his internal rectus muscle 
becomes fatigued and quits, would show an 
exophoria for near. In other words, esophoria 
is a tendency to converge more than the fixing 
point requires. Exophoria is a tendency to fail- 
Figure 4-6. 
ure in producing the amount of convergence 
needed for a definite fixation point. 
Hyperphoria is the tendency of one eye to 
turn up in relation to the opposite eye. 
Esophoria, when not avoided by the fusion 
center, will cause the patient to experience 
homonomous diplopia. Figure 4-6 shows how 
the retinae are stimulated. 
A pair of eyes is trying to focus on A. They 
fail to do so because they have a tendency to 
turn in which, let us say, an exhausted fusion 
center can no longer correct. The image in the 
right eye hits the retina inside the macula. The 
image in the left eye hits inside its macula. 
These points are far from being correspond- 
ing. The final concept of two eyes stimulating 
one brain is diagrammed in figure 4-7. 
Recall that commissural fibers mold the 
maculae of each eye and all other correspond- 
ing points into one psychological concept. 
A little thought will allow you to understand 
why, in an effort to depict physical and psycho- 
logical phenomena in one diagram, some license 
must be granted. Note that the psychological 
projection doubles the physical distance of the 
stimulus off the macula, (figure 4-8.) 
55 AVIATION MEDICINE PRACTICE 
Exophoria, when not corrected by the fusion 
center, produces crossed diplopia (figure 4-9.) 
Figure 4-9.—M = Macula, N = Nodal point, AR = Pro- 
jection for right eye, AL = Projection of left eye, 
A = Point of stimulation. 
Figure 4-7. 
Again recall, the commissural fibres in the 
brain mold corresponding points into one con- 
cept. You work it out for hyperphoria using 
this same logic. 
It has been shown that the fusion center 
of the brain maintains a constant “watch” 
preventing any tendency of the eyes to drift 
off the fix. To determine the presence of any 
such tendency one must weaken or paralyze 
the fusion center. One obvious way to remove 
the effectiveness of the fusion center is to give 
a general anesthetic. While the person is in the 
first stage of a general anesthesia the eyes will 
drift in accordance with this tendency. By this 
observation we could learn the character of the 
phoria but we would have no way of measuring 
the amounts. You might also get the examinee 
drunk. Such a method might be pleasant but 
impractical. 
We are therefore forced to seek some way 
to remove the influence of the fusion center 
without disturbing any other part of the neuro- 
muscular mechanism. This can be done by not 
paralyzing the center but by so “discouraging” 
the center as to make it ineffective. There are 
three quite practical methods of accomplishing 
this. 
1. Change the color of the two retinal im- 
ages; that is, make one red, the other white; 
2. Shorten the exposure time in which the 
two eyes can work together. This is done by 
covering one eye, and by a series of uncover- 
ings, of short intervals, to attempt to catch 
the patient before the correcting “fix” reflex 
is completed. 
3. Change the shape of the image at the two 
retinae. There are many methods of accom- 
plishing this but to save time we will mention 
Figure 4-8.—Homonomous diplopia. 
56 Chapter 4. — OPHTHALMOLOGY IN AVIATION MEDICINE 
only the most practical method: that is, a 
Maddox rod is placed before one eye while the 
examinee looks at a small round, almost point 
source of light about 20 feet away. (The small 
light, often called a muscle light, is a part of 
all modern eye test charts). The Maddox rod 
is nothing more than a very powerful cylinder. 
As a matter of fact, the simplest ones are 
made by snapping a short piece of a glass 
stirring rod into a black blank. 
drift is revealed by subjective response of the 
examinee. The examinee describes to the ex- 
aminer the false protection which is produced 
by the drifting eye. 
Finally, by the use of prisms placed in the 
proper position, the examiner is able to de- 
termine the extent of the drift in diopters. 
Obviously, a drift is as great as the prism di- 
optic power necessary to correct its effect. 
Measurement of phorias.—For actual study 
of this subject the student should have access 
to a modern phonometer such as the one pic- 
tured in the accompanying diagram. If such an 
instrument is not available then an ordinary 
trial frame, a Maddox rod and a series of prisms 
can be utilized by the student to appreciate the 
effect of the phonometer. 
Description of the phorometer.—Most mod- 
ern phonometers are supported on a cross bar 
which in turn is fastened to a floor stand. There 
is usually a gear mechanism provided to move 
the supporting bar back and forth in the hori- 
zontal plane and another to raise and lower the 
upright member which supports the crossbar. 
Usually, before any adjustment can be made 
by either gear mechanism, a thumb screw must 
be released. When adjustment is made so that 
the phorometer is fitted snugly before the face, 
the locks must be tightened to prevent any 
movement during the test. It is especially im- 
portant that the crank for raising and lower- 
ing the vertical member be held in one hand 
while the lock nut is fastened. Failure to take 
this precaution might result in the upright 
member sliding down by its own weight and 
causing a painful blow on the nose of the pa- 
tient. Another precaution for the preservation 
of this very useful instrument is a warning 
to never attempt to move or adjust the moving 
parts of the phorometer without first releasing 
the lock mechanism. Forcefully moving the 
adjustment arms against the hold of the lock 
can strip the gears and do damage to the in- 
strument. 
The basis of the phorometer itself is a heavy 
metal trail frame which is provided with 
grooves to accept three lenses and provision 
for rotating the axis of cylinders. There is also 
a lever for adjustment for the interpupillary 
distance of this frame. In front of each aper- 
Figure 4-10. Simple Maddox rod. 
When a simple Maddox rod is held before 
one eye with the axis of the rod horizontal 
the eye behind the Maddox rod sees a fine line 
vertical in position. The other eye sees the 
small light which is fastened to the wall. In 
other words, the shape of the object is different 
for each eye. The urge to fuse the two is 
greatly decreased. 
It is obvious that the use of all three of these 
methods or a combination of two of the three 
methods does not completely remove the effect 
of the fusion center. However, the fusion cen- 
ter is so discouraged by these methods that 
for all practical purposes it may be considered 
as out of the picture. 
With the controlling influence of the fusion 
center so suspended, the eyes of the examinee 
drift just as they have a tendency to drift. 
The actual determination of the type of the 
57 AVIATION MEDICINE PRACTICE 
Figure 4-11.—PLATE 1. THE PHOROMETER. 
A — Trial frame 
B — Risely prisms on zero position 
C — Thumb screw for adjusting Risely prisms 
D — Multiple Maddox rod 
E —Adjustment fever for Maddox rod 
F — Stephens prism 
G — Adjustment lever for Stephens prism 
H — Adjustment screw to Level Phorometer 
ture of the trial frame, a rotating Risely prism 
is suspended in such a manner that the prism 
mechanism can be put in place before the eye, 
or, when not in use, can be flipped down to the 
side. 
Some knowledge of the working of a Risely 
prism is desirable. It consists of two 15-diopter 
prisms placed in contact and provided with a 
set of gears which are so adjusted that when 
one prism is turned clockwise the other turns 
counterclockwise. A thumb screw is provided 
to facilitate this rotary movement. In one po- 
sition the prisms lie base to base and so pro- 
duce a total of 30 diopters of prism power. 
Turning one prism through 90° would cause 
the other prism to move in opposite direction 
90° and the result is two prisms apex to base. 
The total result of this combination is zero or 
plain thick window glass. By rolling the thumb 
screw on the Risely prism any effect from 
zero to 30-prism diopters can be obtained. 
When the thumb screw of the Risely prism is 
directly vertical and kept in this position the 
rolling of the prisms against each other makes 
possible any amount of base-out or base-in from 
zero to 30 diopters. 
By turning the thumb screw 90° outward to 
the horizontal position, the Risely prisms are so 
placed as to be able to create from 0 to 30 
diopters base-up or base-down. The Risely 
prism is seldom used in this base-up or base- 
down position as will be shown later. It is well 
58 Chapter 4. — OPHTHALMOLOGY IN AVIATION MEDICINE 
Figure 4-12.—Determining the fixing eye. 
59 AVIATION MEDICINE PRACTICE 
to note, however, that by making use of the 
prism on the opposite eye frame, it is possible 
to develop as much as 60 diopters, base-in or 
base-out. 
Students often have difficulty in remember- 
ing which position of the thumb screw pro- 
duces a base-in or base-out effect and which 
position produces base-up and base-down. We 
would call your attention to the fact that when 
the marker of the Risely prism is on 2 you are 
producing 2 prism diopters. When it is on 15 
you are producing 15 prism diopters. If the 
thumb screw is so turned as to produce 30 
prism diopters the bases of the two prisms 
will be in contact with each other. In this situa- 
tion it is quite obvious what “base” position 
you have been producing as you turned the 
thumb screw without disturbing the actual lo- 
cation of the thumb screw. 
Just in front of the Risely prism, and on 
each side, is a Maddox rod. This can be pushed 
up in front of the trial frame and, by making 
use of a tiny handle, the position of the axis 
of the rods can be changed at will. 
The Stephens prisms, the operation of which 
will be described later, under the technique for 
measuring hyperphoria, are so arranged that a 
prism can be thrown up before each eye in a 
single movement of the frame which carries 
them. These prisms are usually used only 
when base-up or base-down effect is desired. 
Technique for using phorometer.—The first 
step is to determine the fixing eye. This is done 
by punching a 1-cm. hole in a large library 
Figure 4-13.—Phonometer is being adjusted. The right hand turns the crank to raise and lower the entire apparatus, 
The left hand guides the head into place. 
60 Chapter 4. — OPHTHALMOLOGY IN AVIATION MEDICINE 
card. The examinee is told to hold the card in 
both hands and to extend his arms fully in 
front. The card is placed in such a position as 
to permit the examinee to sight the small 
muscle light on the wall ahead of him. While 
the card is thus held the examiner covers 
one eye. If the examinee no longer sees a light 
you may assume that the eye chosen for cover 
is the fixing eye or vice versa. 
Next the Risely rotary prism is brought be- 
fore the nonfixing eye. The marker must read 
zero and the thumb screw must be shifted to 
the exact vertical position. With the thumb 
screw in this position the mere rolling of the 
thumb screw will produce prism base-in or 
prism base-out effect, depending upon the di- 
rection of the roll. 
A Maddox rod is now snapped in front of the 
nonfixing eye in such a way as to have the rods 
in the horizontal position. This will cause the 
light entering the nonfixing eye to appear as a 
thin vertical line. (The multiple Maddox rod 
used in most phorometers is nothing more than 
a series of glass rods piled one above the 
other. It has exactly the same effect as a simple 
Maddox rod, but due to its multiple nature, 
exact centering a single rod is spared. In short, 
it is a time saver. If the manufacturer supplies 
a red colored Maddox rod it is obvious that 
only a small card used in covering and cover- 
ing the non fixing eye will permit the use of 
the three practical methods of breaking up the 
effect of the fusion center. 
With the fusion center thus broken, the eyes 
drift. With the Maddox rod in this position we 
are ready to determine the presence or absence 
of any horizontal phoria; that is, esophoria or 
exophoria. 
While the examiner allows the examinee to 
have momentary exposures of the non fixing 
eye, the examinee is requested to report where 
he sees the vertical line in relation to the round 
light. 
it is obvious that the examinee must report 
one of these three possibilities. 
The interpretation of this response must be 
made only after the examiner has taken mental 
note of which eye is behind the Maddox rod. 
In other words, which eye is represented by 
the line? Which by the light? 
If the line is reported to be through the 
Figure 4-15. 
Figure 4-16. 
light no horizontal phoria exists. In such event 
esophoria is zero and exophoria is zero. Such 
a finding is rare. 
If the Maddox rod is before the right eye and 
the patient reports this the examiner concludes 
that esophoria homonomous diplopia is present. 
The short periods of uncovering of the nonfix- 
ing eye are continued while the prism power 
base-out is gradually increased. When the pa- 
tient reports the line to be through the light 
the examination is complete. The Maddox rod 
is flipped out of place and the amount of eso- 
phoria is read off in prism diopters and re- 
corded. 
If the patient reports this, exophoria crossed 
diplopia is present and the Risely prism is 
turned so as to produce a base-in effect. When 
the line is reported as passing through the 
light, the amount of exophoria has been de- 
termined and is read off at the marker on the 
Risely prism. 
Notice that crossed diplopia indicates ex- 
ophoria and an uncrossed or homonomous di- 
plopia indicates esophoria. (figure 4-8 and 4-9.) 
A simple noematic is here suggested by spell- 
ing 
e X ophoria 
The capital X might help to remind you that 
exophoria produces crossed diplopia. If the 
Maddox rod is before the right eye and the ex- 
Figure 4-14. 
61 AVIATION MEDICINE PRACTICE 
Figure 4-17.—Taking lateral phoria measurement. Note the thumb screw of the Risely prism is in vertical position. 
The eye is uncovered only for short Intervals by raising the card. 
Figure 4-19. 
The Maddox rod is now replaced to a position 
in front of the nonfixing eye. The direction 
of the rod is changed so that the axis of the 
rod is vertical. The covering and short ex 
posures of the nonfixing eye is again resumed. 
The examinee now indicates one of these three 
conditions. 
Again remember that your interpretation of 
the examinee’s response depends upon which 
eye is behind the Maddox rod. 
Figure 4-18 
aminee reports the line to the left of the light 
the diplopia is obviously a crossed type. 
No person can have both esophoria and exo 
phoria for the same point of fixation at the 
same time. To report such a situation will dis- 
play either carelessness or ignorance on the 
part of the examiner. 
62 Chapter 4. — OPHTHALMOLOGY IN AVIATION MEDICINE 
Figure 4-20.—Taking Vertical phoria measurement. Only the Stephens prism is being used. The eye is uncovered for 
short Intervals by dropping the card. 
In regard to vertical phorias only three pos- 
sibilities exist: 
1. Right hyperphoria 
2. Orthophoria (no phoria) 
3. Left hyperphoria 
The term hypophoria is hardly ever used in 
ophthalmology. If you consider that a person 
possesses the tendency for his left eye to drift 
down in relation to his right eye you may de- 
scribe the same phenomenon by stating that the 
right eye has a tendency to drift up in relation 
to the left eye. Left /iT/pophoria is the same as 
right fo/perphoria, just as six is the same as 
half dozen. This is a mind twister which stu- 
dents find it hard to appreciate. Think it over. 
It is an accepted ophthalmological fact. 
Now let us return to the response of our 
examinee. The Maddox Rod is now with its 
axis vertical. If the patient sees the line through 
the light you may conclude that no phoria is 
present. This is recorded. 
R. H. (right hyperphoria) = zero 
L. H. (left hyperphoria) = zero 
If the patient reports this 
Figure 4-21. 
Reflect for a moment: the right eye is behind 
the Maddox rod. It is obvious from the above 
response that the line of the Maddox Rod must 
be falling on the retina of the right eye above 
the macula. If this is so then the right eye must 
be turned up in relation to the left eye—hence 
a diagnosis of right hyperphoria. 
63 AVIATION MEDICINE PRACTICE 
Now we must determine how much prism is 
necessary to correct this discrepancy. A prism 
placed base-down before the right eye will ac- 
complish this correction. When you add enough 
base-down prisms before the right eye to move 
the retinal image of the line down to meet the 
right macula the patient will see this. 
prisms are usually 1 prism diopter each and 
are mechanically set so that when one is base- 
down the other is base-up. Therefore, in rotat- 
ing these prisms, one against the other, any 
amount of correction from zero to 2 prism di- 
opters may be accomplished. 
It is obvious that, when you have used the 
Stephen’s prisms to their maximum, and still 
have not measured the full extent of vertical 
phoria present, you will have to augment the 
Stephen’s prism with the Risely prism. Before 
such augmentation is possible you must set 
the Risely prism in such a way that it will pro- 
duce base-down or base-up effect; that is, the 
thumb screw must be horizontal. Furthermore, 
you are cautioned in so augmenting the 
Stephen’s prism that you make sure that the 
Risely prism is producing the proper effect; 
that is, base-up or base-down, according to 
which is needed, and before the proper eye. 
There is one more useful test which is made 
on the phorometer. That is the determination 
of prism divergence. This is simply a measure 
of the amount of prism a person can take in 
the horizontal position without developing di- 
plopia. In short, it is a measure of power or 
limit of divergence of the eyes which can be 
accomplished by any individual. For this test 
we purposely do not try to break fusion. The 
Risely prism is set at zero and placed before 
the non fixing eye with the thumb screw turned 
to the vertical position. The examinee is told 
to look at the small muscle light with both eyes 
and to speak up when he is conscious of a break 
into two lights. The Risely prism is evenly, and 
fairly briskly, rotated to produce a base-in ef- 
fect. When the candidate indicates a break, stop 
your rotation and read off the amount of prism 
power employed. Most candidates notice the 
break very suddenly, at which time the spread 
of the two images becomes so great that the ex- 
aminee will request a retest. He will state he 
thinks he has missed informing you at the ex- 
act time at which the break actually occurred. 
Usually, however, this is an illusion, and the 
first reading is the correct one. More than two 
attempts to get a reading will cause fatigue 
and any subsequent reading without rest will 
be definitely false. 
Why is such a finding of interest in a physi- 
cal examination of aviators? Well, if a candi- 
Figure 4-22. 
The amount of prism employed will indicate 
the extent of the hyperphoria in prism diopters. 
If under the same conditions (that is, Maddox 
rod before the right eye) the patient reports 
the line above the light. 
Figure 4-23. 
Your diagnosis is left hyperphoria and the ex- 
tent will be indicated by the amount of prism 
base-up before the right eye as is necessary to 
correct the discrepancy. The noematic for ver- 
tical phoria is— 
“The lower image indicates hyperphoria of 
the eye which that image represents.” 
At this point we must call your attention to 
the fact that any vertical phoria which is of 
such a character as to be corrected by a 2- 
diopter prism base-down before the right eye 
and no prism before the left eye: such a phoria 
can also be corrected by two diopters base-up 
before the left eye and no prism before the 
right. Furthermore, the proper correction may 
be equally divided before each eye; in this ex- 
ample, one diopter base-down before the right 
eye and one diopter base-up before the left eye. 
Expressed in symbols: 
2 V left = 2 A right = 1 V left with 1 
A right 
This fact is employed in the modern phoro- 
meter in the form of a Stephen’s prism. These 
64 Chapter 4. — OPHTHALMOLOGY IN AVIATION MEDICINE 
Figure 4-24.—Shows the Risely prism in position to augment the Stephens prism. Note the thumb screw of Risely prism 
is horizontal. 
Figure 4-25.—Taking prism divergence. The Risely prism is producing base In effect which Is being steadily increased. 
65 AVIATION MEDICINE PRACTICE 
date is found to have an esophoria it is as- 
sumed that the tendency to drift will be com- 
pensated without symptoms if that person pos- 
sesses sufficient divergence power to offset this 
drift. We will discuss standards later but can 
say now that we require a person who has eso- 
phoria to be balanced by as much prism di- 
opters of divergence power as he has esophoria. 
Notice that up to now we have been dis- 
cussing phorias and prism divergence on a dis- 
tant target. At the present time serious con- 
sideration is being given to the need for run- 
ning these tests at reading distance too. This 
thought is based on the fact that the modern 
aviator must read charts and instruments al- 
most as much as he uses his eyes for distance 
vision. The examination of phoria for near, 
though not at present required, could be done 
by using the exact technique as described 
in the foregoing pages except that the target 
light, instead of being 20 feet away, would be 
the small light of an ophthalmoscope, with 
the head removed, and held at about 15 inches 
from the examinee’s eyes. 
COMMENTS ON PRESENT STANDARDS 
The amount of phoria which a candidate may 
have in order to pass an examination for quali- 
fication for flight training was set by a board 
of prominent ophthalmologists during the first 
World War. They have stood the test of time, 
A recent research project1 revealed the fact 
that of 250 aviators who came back alive from 
extensive combat missions in World War II (a 
good criterion for classifying them as success- 
ful) almost all of them were found to be within 
present standards. This indicates that our pres- 
ent standards are not too rigid. Some claim 
they are not rigid enough. The present stand- 
ards and their applications may be explained 
as follows: 
1. Esophoria: A candidate may have as 
much as 10 diopters of esophoria but if it is 
over 4 diopters he must be able to pass a “red 
lens test.” Furthermore, any candidate who has 
esophoria must have prism divergence power 
of equal amount. That is, if he has an esophoria 
of 5 diopters he must have a prism divergence 
of 5 diopters or better. If the esophoria is under 
4 diopters a red lens test is not required but 
the requirement for equal amounts of prism di- 
vergence still holds. 
2. Exophoria: An exophoria of over 5 di- 
opters disqualifies the candidate. Five diopters 
or less is acceptable. 
3. Hyperphoria: Hyperphoria of more than 
one diopter disqualifies. Hyperphoria of one di- 
opter or less is acceptable. 
4. Prism Divergence: This power must be 
at least two diopters. Under two diopters dis- 
qualifies. However, if the power of divergence 
is greater than 15 diopters the candidate is 
also disqualified. 
Prism convergence is not a part of the avia- 
tion physical examination. The angle of con- 
vergence is used in its place. 
Angle of convergence (power of convergence 
or power of adduction).—The angle is com- 
puted from; 
Near point of convergence (PcB) 
Interpupillary distance (Pd) 
The near point of convergence is represented 
by the symbol PcB (punctum convergens basa- 
lis), meaning the near point of convergence to 
the base line. This measurement is made from 
an imaginary line connecting the centers of 
rotation of the two eyes, situated 13.5 mm. 
behind the anterior surface of the cornea. The 
idea is to determine the greatest amount of 
convergence that can be exerted and still main- 
tain binocular single vision. 
Near point of convergence.—The end of the 
Prince rule, or a modification of same, is 
placed edge up at the side of the nose 111/2 mm. 
in front of the anterior surface of the cornea. 
A white headed pin is held 33 cm. in the median 
line above the edge of the rule, and the exam- 
inee is instructed to look at it intently. If 
both eyes are seen to converge upon the pin, 
it is then carried in the median line along the 
edge of the rule, towards the root of the nose. 
The examinee’s eyes are carefully watched, and 
the instant one is observed to swing outward 
the limit of convergence has been reached. The 
point on the rule opposite the pin is then read 
in millimeters. This test is repeated until a 
fairly constant reading is obtained. Usually 
the first or second try is correct and as the 
1 Imus, Henra A. “Visual Exam of Flyers Returned from 
Combat”, BuMed Research Project X-395, The Journal of Avia- 
tion Medicine, April 1948. 
66 Chapter 4. — OPHTHALMOLOGY IN AVIATION MEDICINE 
trial is repeated the muscles become fatigued 
and the PcB gradually becomes more remote. 
To the reading thus obtained 25 mm. are added, 
(the center of rotation is 13.5 mm. behind the 
cornea and the end of the rule is placed 11.5 
mm. in front of the cornea making a total of 
25 mm.), which gives the distance from the 
near point of convergence to the base line. 
The normal eyes should be able to converge 
to 75 mm. or less. A near point more remote 
than 75 mm. indicates an under action of the 
internal recti. 
Interpupillary distance. — The examiner 
stands with his back to the light, face to face 
with the examinee. The rule is laid across the 
examinee’s nose in line with his pupils, as 
close to the two eyes as possible. The distance 
is measured from the nasal side of one pupil to 
the temporal side of the other. The examiner 
closes his right eye and instructs the examinee 
to fix his eyes upon his open left. With the 
eyes in this position a predetermined mark on 
the rule (preferably zero) is placed in line with 
the nasal border of the examinee’s right pupil. 
The rule must be held steadily in this position 
while the examiner opens his right eye and 
closes his left. The examinee is then instructed 
to look at the open right eye. The point on 
the rule in line with temporal border of the 
examinee’s left pupil is read in millimeters. The 
distance between the two points on the rule is 
the interpupillary distance. 
The following formula is used to compute the 
angle of convergence: angle of convergence 
equals one-half the interpupillary distance 
multiplied by 100, divided by the near point 
of convergence, plus three, thus: 
i/2Pd. X 100 
plus 3 = Angle of convergence 
FcB 
The above formula for determining the angle 
of convergence is purely empirical, and it is 
not accurate from a standpoint of pure mathe- 
matics. It is fairly accurate when PcB and 
Pd are approximately equal. It is suggested 
that the table showing the angles of conver- 
gence with different findings as to Pd and PcB 
be used instead, as this table is computed 
accurately from tables of tangents. 
An angle of convergence of less than 40° is 
undesirable. If associated with exophoria in 
Figure 4-26. 
the upper limits, an agnle of convergence of 
less than 40° will call for a red lens test to be 
run. In short, we figure the angle of conver- 
gence in order to determine whether or not 
a red lens test must be done. For computation 
table see figure 4-27. 
These standards and others are recorded else- 
where in these notes in simpler terms which 
can be noted in a glance. 
In addition to its use in an aviation physical 
examination, the phorometer is a valuable aid in 
physical diagnosis. The presence of a hyper- 
phoria of over 1 diopter may explain the head- 
ache—the cause of which you have been search- 
ing elsewhere. The absence of any abnormal 
phoria eliminates that possibility of explaining 
a headache on that basis. Familiarity with the 
phorometer wll give accurate information in a 
few minutes. Lack of familiarity with its 
principles and markings can cause you to take 
an hour to get that same information. 
Finally, for those who wish to check the eye 
glasses that a patient is wearing or to prescribe 
a change of lens, phorometer readings are of 
considerable importance in deciding upon the 
final prescription. 
REVIEW QUESTIONS 
1. Name three methods used to discourage the fusion 
center. 
2. Which concept does an uncompensated exophoria 
produce—crossed, or homonomous ? 
3. A patient behind a phorometer with the Maddox 
rod before the right eye sees the line above the light. 
What kind of hyperphoria does he have—left, or right? 
67 AVIATION MEDICINE PRACTICE 
Figure 4-27.—Table for computing angle for convergence. 
68 Chapter 4. — OPHTHALMOLOGY IN AVIATION MEDICINE 
4. How would you place a prism to correct esophoria 
—base-in ? Base-out ? 
5. How would you place a prism before the left eye 
to correct left hyperphoria—base-up? Base-down? 
6. What is the limit of hyperphoria for qualifications 
for flying? 
7. What is the limit of esophoria? 
8. If a person has 18 diopters of prism divergence, 
is he qualified? 
9. If a person has esophoria 4 and prism divergence 
of 3, is he qualified? 
10. Before which eye is the Maddox rod placed— 
fixing, or nonfixing? 
11. Why is adequate prism divergence for near nec- 
essary to the modem flyer? 
ASSOCIATED PARALLEL MOVEMENTS 
AND THE RED LENS TEST 
An aviator during flight is constantly scan- 
ning the sky for approaching planes. Therefore, 
normal associated parallel movements are an 
important feature in his physical make-up. 
These movements are grossly checked during a 
physical examination by the simple confronta- 
tion test. The examiner faces the patient and 
watches the candidates eyes while a small test 
stimulus such as the eraser of a pencil is 
moved in the six cardinal directions of gaze. 
1. To left in the horizontal. 
2. To right in the horizontal. 
3. Up and to the right. 
4. Down and to the left. 
5. Up and to the left. 
6. Down and to the right. 
If any overshooting or undershooting is noted 
the patient must be subjected to further test- 
ing of a more accurate nature. If, in checking 
the phorias, the examiner has found the candi- 
date to have a phoria which approaches the 
upper limit for qualification, this same more 
accurate test for associated parallel movements 
is indicated. The confirmatory test chosen for 
this purpose is the so-called “red lens test.” 
In order to fully understand this test a brief 
discussion of the anatomy and physiology of 
the six extrinsic muscles of the eye is almost 
essential. The movements of the eyeball are 
termed as follows: upward rotation or eleva- 
tion, downward rotation or depression, out- 
ward rotation, inward rotation and a twisting- 
movement on the AP axis termed torsion. In 
torsion is defined as an inward rolling of the 
12 o’clock position of the cornea. Ex-torsion 
is the opposite. 
Let us consider the superior rectus muscle in 
detail. The origin of this muscle is the bone 
around the optic foramen. The muscle courses 
forward and outward to insert into the sclera 
of the ball about 7.5 mm. posterior to the 
corneal margin. It is obvious that the main 
function of this muscle is elevation. However, 
in an “eyes front” position the line of the 
muscle action crosses inside or nasal to the 
functional center of rotation of the ball. This 
fact accounts for the assignment, when the ball 
is in the “eyes front” position, of two auxiliary 
actions to this muscle, i.e., inward rotation and 
in-torsion. When the eye is, however, rotated 
outward, the functional center of rotation of 
the ball slips under the line of pull of this 
muscle. With a little thought you will appre- 
ciate that when the functional center of rota- 
tion of the ball is exactly in line with the ori- 
gin and insertion of the muscle, the auxiliary 
actions of the superior rectus muscle are lost 
and it becomes solely an elevator. A little’ more 
thought will give justification to the statement 
that as an eye rotates outward the superior 
rectus muscle gradually loses its power of aux- 
iliary action and gains in mechanical advan- 
tage to accomplish its main action. In other 
words the field of action of the superior rectus 
(the area where the muscle is exerting is main 
action at its best) is up and out. 
In addition to the superior rectus muscle 
there is only one other elevator for the eyeball 
well forward in the lower portion of the boney 
—the inferior oblique. That muscle takes origin 
orbit at a point immediately lateral to the fossa 
of the lacrimal sac. It passes under the eyeball 
backward and outward to wrap partly around 
the ball, passing inside the functional center 
of rotation to insert in the sclera in the pos- 
terior upper-outer quadrant. The main action 
of this muscle is upward rotation or elevation. 
Like the superior rectus, and by the same line 
of reasoning as indicated for the superior rec- 
tus, the inferior oblique muscle has the auxil- 
69 AVIATION MEDICINE PRACTICE 
ACTION OF EXTRINSIC MUSCLES 
Muscle 
Main Action 
Subsidiary Action 
Field of Action 
Superior Rectus 
Inferior Oblique 
Inferior Rectus 
Superior Oblique 
External Rectus 
Medial Rectus 
Elevation 
Elevation 
Depression 
Depression 
External Rotation 
Internal Rotation 
Internal Rotation Intorsion 
External Rotation Extorsion 
Internal Rotation Extorsion 
External Rotation Intorsion 
None 
None 
Up and Out 
Up and In 
Down and Out 
Down and In 
Out 
In 
Note that the external rectus and medial rectus have no auxiliary action. 
liary actions of outward rotation and extorsion. 
As the eyeball is turned inward the auxiiiiary 
actions of the muscle fade in mechanical ad- 
vantage until at a certain point the inferior 
oblique is solely an elevator of the eye. For 
this reason the field of action of the inferior 
oblique is up and in. 
Similar analysis for the remainder of the 
extrinsic muscles will permit you to appreciate 
in your mind the facts presented in the ac- 
companying chart. 
The most useful fact to remember from a 
clinical point of view is the field of action of a 
muscle. It is often difficult for the student to 
appreciate that the resultant of the normal and 
auxiiiiary actions of a muscle is not the field 
of action. In a normal individual no eye move- 
ment is ever the result of the action of a single 
muscle. All six extrinsic muscles contribute to 
any movement of the normal eye. As one muscle 
contracts, other muscles called synergists help 
with the movements. At the same time antag- 
onists relax proportionately. The result is a 
smooth and purposeful movement. There is no 
jerking and cessation of movement is accom- 
plished sharply when the desired direction of 
gaze is reached. It is true, however, that in 
certain extreme directions of gaze one muscle 
carries the load more than others. It is sound 
deductive reasoning to assume that when an 
eye fails to follow in any particular direction 
of gaze, that muscle which is responsible for 
the field in which failure occurs is weak. 
The basis for the explanation of the red lens 
test is the application of this deductive reason- 
ing. The test will reveal: 
i 1. Any failure to maintain associated paral- 
lel movements of the eyes. 
2. What particular muscle is involved. 
3. Is the involved muscle weak or is it over- 
acting ? 
Since there are six extrinsic muscles for each 
eye, there are six fields of action. Test move- 
ments into these fields are called the six cardi- 
nal directions of gaze. If you stand behind your 
patient and imagine the movements of his eyes 
in the six cardinal directions you can readily 
diagram the muscles responsible for each field 
in this manner. 
Figure 4-28. 
Recalling the diagram from this aspect will 
be more useful. It may help in preparing this 
diagram if you will memorize the fact that 
the fiield of action of the oblique muscles is al- 
ways nasal. 
Technique of the test.—Any smooth surface 
such as a blackboard or tangent screen can be 
used. A chalk point or a white pin is used as 
a central point. The patient is seated 75 cm. 
from the surface and the right eye is covered 
by a red lens. This may be done by using a 
trial frame and a red lens from the trial lens 
box, or by improvising a red celluloid monocle 
to be held over the patient’s right eye. The 
patient’s head must be kept motionless. This is 
accomplished by improvising a head rest or by 
having an assistant hold the patient’s head. A 
70 Chapter 4. — OPHTHALMOLOGY IN AVIATION MEDICINE 
Figure 4-29.—Candidate holding improvised red lens before his right eye. He holds his head motionless. Only his eyes 
move and try to follow the stimulus. 
71 AVIATION MEDICINE PRACTICE 
Figure 4-30.—Red Lens Test.—Paralysis of right external rectus. Diplopia increases as stimulus moves out into field 
of that muscle. 
72 Chapter 4. — OPHTHALMOLOGY IN AVIATION MEDICINE 
dimly lighted room makes the test easier. The 
tiny electric light of an ophtlalmoscope, with 
the head removed, acts as an excellent stimulus. 
The stimulus is held at the central point and 
the presence or absence of diplopia is noted. 
The normal person will see a single pink light. 
Diplopia in this primary position usually means 
a tropia exists but it may mean only phoria. The 
stimulus is moved slowly from the central point 
into one of the cardinal directions of gaze. The 
patient is asked to report immediately the 
presence of diplopia. When the stimulus has 
been moved 50 cm. from the center of fixation, 
without the occurrence of diplopia, the stimu- 
lus is brought back to the center and another 
field is explored. If diplopia does not occur 
in any cardinal direction within 50 cm. of the 
central point, the associated parallel movements 
of the eyes is considered normal and the pa- 
tient is qualified. 
If diplopia occurs inside the 50 cm. range, 
the operator, by a series of questions, locates 
the position of the red light and the position 
of the white light. The answers to this series 
of questions are often a challenge to the opera- 
tor’s patience and intelligence. (You can point 
to the false image in order to help the patient 
locate it. If you point to the true light stimulus 
the patient will see two pointers. If the image 
exactly over the location of the light is red 
the patient is fixing with his right eye and the 
second image is false. The location of the two 
images are marked and the movement of the 
stimulus is resumed to a point about 20 cm. 
further in that particular cardinal direction. 
Again the true and false images are located and 
marked. 
The formation of a false image which in- 
creases in separation distance from the true 
image indicates abnormality in the eye which 
sees the false image. The field of action in which 
the diplopia increases indicates the muscles in- 
volved. Finally, if the diplopia is crossed the 
abnormal muscle is underacting (weak or para- 
lyzed). If the diplopia is homonomous, the ab- 
normal muscle is overacting. (This latter find- 
ing is infrequent.) 
If you do not quite understand all this do 
not be too discouraged. It is not essential that 
the flight surgeon diagnose the particular 
muscle which causes the increasing diplopia, 
even though such information is of considerate 
clinical interest. The mere presence of diplopia 
occurring in any direction within 50 cm. of the 
central fixation point is disqualifying. In apply- 
ing this standard, however, you are reminded 
that the patient must be exactly 75 cm. from 
the surface used for charting. 
Diplopia, which first occurs beyond 50 cm. 
from the fixation point is not disqualifying. 
This extreme direction of gaze is never used 
normally. Furthermore, failure to maintain 
fusion in the extreme portions of the field is 
probably due to the normal effect of the check 
ligaments. 
VISUAL FIELDS 
Accurate studies of visual fields are time 
consuming. They have never been considered a 
part of a routine physical examination. How- 
ever, many times after completing a thorough 
physical examination, you have unveiled in- 
formation which calls for a visual field study. 
For these same reasons, careful visual field 
studies are only made a part of the flight physi- 
cal when other tests indicate the necessity of 
such study. 
The instructions call for a confrontation test 
and grossly checking the visual fields of each 
eye. The examiner looks directly into the right 
eye of the examinee while he keeps his own 
right eye and the patient’s left eye covered. 
While holding this gaze a test object is roughly 
moved through the entire visual field with the 
examiner using his own field as a control. If 
any discrepancy is noted on this test it is neces- 
sary to run a complete perimetric study. Any 
unusual appearance of the fundus upon exam- 
ination would also call for perimetric studies— 
especially if the character of the lesion be 
doubtful. Whenever cupping of the disc is 
noted with the opthalmoscope or any increase 
in interocular pressure is suggested by palpa- 
tion, visual field studies are always necessary 
for they may unveil sufficient findings to justify 
any early diagnosis of glaucoma. 
As one would naturally expect, a person who 
has pathology sufficient to show up in a visual 
field tracing does not usually present himself 
73 AVIATION MEDICINE PRACTICE 
for flight training. Therefore, the test is sel- 
dom run in routine physical exams. 
However, when a field tracing is needed it is 
usually needed badly. Not only flight surgeons 
but every doctor who has a perimeter available 
should be sufficiently acquainted with the tech- 
nique of testing as to be able to perform the 
test without having to reach for a book of in- 
structions. 
Perimeters are built of various sizes. The 
eye of the patient must be placed at the 
distance from the fixation point for which 
the perimeter was designed. The most com- 
mon sizes are 25 cm. arc. and 33 cm. arc. 
The patient’s head must be securely fixed 
by the chin rest and the patient must be 
comfortably seated. The size of the stimulus 
is important. Often stimuli are found in clinics 
which are marked in degrees. The examiner 
must make sure that such stimuli are correct 
for the size instrument used. A V^-degree stim- 
ulus for a 33 cm. instrument would measure 
3 mm.; such a stimulus would be %-degree for 
a perimeter of 25 cm, arc. Since a change in 
visual field is as important a diagnostic sign 
as the actual character of the constriction, the 
same size stimulus must be used for subsequent 
examination. Only then can repeated fields be 
compared. 
A little patience in explaining to the patient 
what he is to do will save time in the end. The 
patient must be trained to keep his eye glued 
on the fixation point. The stimulus is brought 
from the unseen to the seen. Show the patient 
that in doing a tracing for white, or the so- 
called “form” field, the stimulus will first ap- 
pear gray and then a definite white. The first 
appearance of definite white indicates the point 
to be recorded for any one meridian. Run 
through the vertical and horizontal meridians— 
then the four obliques. If these are all normal 
you may assume no gross constriction. If one 
of these appears to be constricted it might be 
well to run a few more meridia to either side 
of the constriction. 
The size stimuli suggested in these notes are 
only intended as a guide. The smallest stimulus 
which brings out the largest field should be 
used. Once a size stimulus has been chosen a 
note to that effect must be made on the record. 
Don’t forget to record the name and date. There 
is nothing more discouraging than getting two 
chartings mixed up so that both have to be done 
over. 
For the interpretation of discrepancies in 
visual fields the reader is referred to complete 
texts on the subject. For the guidance of the 
flight surgeon any constriction of greater than 
15° in any meridian disqualifies a candidate 
for flight training. 
Beside studying the gross form of the visual 
fields as accomplished by perimetric studies, a 
further study must be made of the field which 
is functioning. For this purpose the tangent 
screen is a more practical clinical aid than 
the perimeter. 
Tangent screens are prepared for these stud- 
ies in two common sizes: a smaller one designed 
for a patient placed 50 cm. from the tangent 
screen and a larger type designed for 100 cm. 
working distance. One may construct a tangent 
screen of any size desired but the sizes men- 
tioned are most commonly used. 
Most tangent screens are constructed by 
stretching a black cloth over a supporting 
frame and marking out circles which represent 
various distances in degrees from the fixation 
point. These circles are nothing more than 
projections of the scale of the perimeter arc 
on a flat surface. It is obvious that the screen 
will accurately serve only for tracing defects 
in the central portion of the visual field; that 
is, defects within 30° of the center of fixation. 
Working on a flat surface, the examiner may 
rapidly cover the central portion of the fields 
in search for scotomata. These are pathological 
anywhere except the physiological scotoma or 
blind spot. Any scotomata found are easily 
marked out by the use of common pins. The 
size of the blind spot is of considerable clinical 
interest. It is enlarged in many disease condi- 
tions such as glaucoma, papillitis, and papil- 
ledema. Any enlargement of the blind spot of 
more than 2° above average is considered as 
pathological. A 14-degree stimulus is suggested 
for this type study. It gives more accurate 
tracings. In tracing out a scotomatous area 
it is well to remember that the stimulus should 
be passed from the unseen to the seen. 
74 Chapter 4. — OPHTHALMOLOGY IN AVIATION MEDICINE 
Existing standards permit the individual 
flight surgeon to decide what size small scotoma 
would disqualify the candidate for flying. How- 
ever, a scotoma involving more than 15° of any 
meridian is automatically disqualifying. The 
decision on smaller scotomata would be made on 
the basis of etiology. Ordinarily no scotomata 
are expected, and the presence of scotomata 
always calls for assurance of the examiner that 
they are not due to a progressive disease. If 
there is any doubt on this score the patient 
should be disqualified. An old healed chorioret- 
initis, especially if it occurs in the nasal field 
might be disregarded if there are no other 
symptoms. It would be wise however to refer 
a person with a scotoma to an ophthalmologist 
for consultation before passing him. 
We speak of fields of vision as temporal field, 
nasal field, upper field and lower field. One must 
keep constantly in mind that the temporal 
visual field represents a diagram of the func- 
tion of the nasal retinal areas. The physiologi- 
cal blind spot which represents the entrance of 
the optic nerve into the eyeball is in the tem- 
poral visual field for it represents a part of the 
nasal retinal area. 
The following notes are given to each student 
for reference during the lecture on this subject 
at the School of Aviation Medicine, Pensacola, 
Florida. They contain pertinent information.. 
USEFUL DATA FOR 
PERIMETER 
AND 
TANGENT CURTAIN 
The perimeter—used for peripheral field study. 
For White use 1/00 stimulus 
For Blue 
Red use 1° stimulus 
Green 
Formula for calculating stimuli where 
S = Stimulus in millimeters 
D = Stimulus in degrees 
R = Distance of patient from the fixation 
point in mm. 
H = 3.1416 
then 
S x 180 
D = n r 
and 
H R D 
Q 
180 
The perimeter is usually used at 330 mm. 
The tangent screen is usually used at 1000 mm. 
Therefore use: 
33 cm. 
Perimeter 
1 Meter 
Tangent Screen 
Form 
V20 — 3 mm. 
1° = 6 mm. 
V20 — 9 mm. 
1° — 18 mm. 
Color 
Scotoma & 
Blind Spot 
M° = 4.5 mm. 
With the following information you can make 
a tangent screen for any desired distance. The 
radius of each degree circle in millimeters is 
determined by multiplying the distance from 
the fixation point by the natural tangent. 
Natural tangent 5° = .0875 
10° = .1763 
15° = .2638 
15° = .3640 
25° = .5050 
30° = .5774 
To locate the blind spot: 
From fixation point to proximal margin 
of blind spot 13.5° 
Width of blind spot 5° 
Height of blind spot 7° 
Portion of blind spot above the horizontal 2° 
Portion of blind spot below the horizontal 5° 
Measurements of blind spot for 1-meter 
tangent screen: 
From fixation point to proximal margin 
of blind spot 232 mm. 
Width of blind spot 89 mm. 
Height of blind spot 122 mm. 
Portion of blind spot above the 
horizontal 33 mm. 
Portion of blind spot below the 
horizontal 89 mm. 
Normal limits of peripheral fields are: 
75 AVIATION MEDICINE PRACTICE 
of another plane are essential factors for the 
practice of accurate gunnery. 
Many factors usually are combined before 
a final estimation of depth is accomplished. 
The stimuli which register in various parts of 
the nervous system are subconsciously com- 
bined and the distance of an object from the 
eyes is estimated in a flash. 
For the purpose of study the various factors 
which combine to produce the estimation of 
depth can be classified as adjunctive and basic. 
Adjunctive factors are those which depend 
upon a comparison or, better, the relation, of 
one outside object to another object outside the 
eye. 
Basic factors are those which depend only 
upon the observer’s perception apparatus and 
the object under estimation. These factors 
operate without dependence on other objects 
in the visual fields. Therefore, they are the 
only means of estimation of distance for a 
single ship on the horizon or a single plane in 
the air. 
We would like first to explain briefly the 
various adjunctive factors. One example of 
an adjunctive is the comparison of the size of 
the retinal image of two objects. Based on ex- 
perience, we know that a railroad car has a 
definite relation in size to that of another 
familiar object—a man. When a railroad car 
appears to be only as high as a man—the car 
is, of course, interpreted as being farther away 
than the man. 
Another adjunctive factor is motion paral- 
lax. When you focus on a near object and 
move your head to one side, objects in your 
visual fields farther away than the object fo- 
cused upon move with the movement of the 
head. Objects nearer than the object focused 
upon move against the movement of the head. 
Hold a finger from each hand before you and 
convince yourself by experiment. 
Mathematical or linear perspective is an- 
other adjunctive factor. An example of this is 
the apparent meeting of the railroad tracks at 
a distance. We know they do not meet and, 
therefore, obtain a clue from the fact that they 
appear to meet. Aerial perspective helps us 
to judge distance. Our experience with various 
atmospheric conditions have taught us that for 
a given atmospheric condition, an object which 
White (form) 
Blue 
Red 
Green 
Upper 
Nasal 
I ,nwpr 
50 
30 
25 
15 
60 
35 
25 
20 
70 
35 
30 
25 
Temporal 
90 
50 
40 
30 
Pertinent signs to aid localization of pathology: 
1. Disturbance of choroid—scotoma for blue. 
2. Early axon or nerve fibre pathology— 
contraction of red. 
3. Papillitis & papilledema—enlargement of 
blind spot. 
4. Lesion in chiasm—hemianopsia. 
5. Lesion in optic tracts—hemianopsia and 
quadrantanopsia. 
6. Thrombosis or embolism in branch artery 
or vein—sector effect in one eye only. 
7. Chronic pressure from glaucoma—con- 
traction of nasal fields, enlargement of blind 
spot, Paracentral scotoma. 
8. Hysteria—gun-barrel vision. 
9. Any enlargement of blind spot of over 
2° is cause for suspicion. 
QUESTIONS FOR REVIEW 
1. What size stimulus is usually used for form 
fields ? 
2. What size stimulus is usually used for color 
fields ? 
3. Why is the exact size of stimulus used and dis- 
tance employed important for making reports? 
4. Name two common causes for enlargement of the 
blind spot. 
5. What is the criterion for assuming that a blind 
spot is enlarged? 
6. What is the advantage of the tangent curtain 
in studying visual fields? 
7. What are the limitations of tangent curtain 
studies? 
8. What size stimulus would you use to trace the 
blind spot on a one-meter tangent curtain? 
9. What is the limit of contraction of visual field 
allowed for aviation? 
10. In which visual field does the physiological sco- 
toma appear? 
DEPTH PERCEPTION 
Good depth perception is important for the 
successful performance of an aviator. It is im- 
portant in making landings, in flying forma- 
tions, in determining the distance of an ap- 
proaching plane so that collision in air might be 
avoided. The distance and speed of approach 
76 Chapter 4. — OPHTHALMOLOGY IN AVIATION MEDICINE 
is surrounded partly by fog but still visible 
is a certain distance away. On a clear day the 
mountain tops appear to be surrounded by a 
blue haze. We know by experience that an 
object which is surrounded by haze on a clear 
day must be a great distance away. 
You will note that all these adjunctive factors 
are available for persons having one eye. In 
fact, if we add the factor of accommodation to 
the four previously mentioned factors we have 
the total mechanism available for monocular 
depth perception. Accommodation contributes 
to the impression of depth by means of the 
steriognostic sense produced by ciliary contrac- 
tion. It is, of course, only of aid when the 
object to be estimated is within 20 feet of the 
observer. For objects further away than 20 
feet the amount of accommodation needed for 
focus is so small as to give practically no clue. 
For monocular vision, therefore, we have the 
following factors available for the estimation 
of depth; (1) size of image, (2) motion paral- 
lax, (3) mathematical or linear perspective, 
(4) aerial image, (5) accommodation. 
It was because of these factors that such 
persons as the famous Wiley Post and other 
aviators who have lost an eye are still able to 
fly. These factors do not accomplish very ac- 
curate depth perception. Their accuracy de- 
pends a great deal on the personal element— 
that is, the alertness of the individual—and 
also on his experience. The availability of these 
factors might permit experienced aviators who 
have lost an eye to fly but it would not be wise 
to allow a one-eyed person to start training. 
The most accurate depth perception is ac- 
complished by the factors available only with 
binocular vision. The man with binocular vi- 
sion has all the adjunctive factors and accom- 
modation available but he also has— 
Physiological diplopia 
Binocular parallax 
Stereoscopic vision 
Convergence 
to help him in his final decision of the depth 
of an object in space. 
Physiological diplopia.—When a person fo- 
cuses on a certain object the line of vision 
passes through the nodal point to the macula 
of each eye. If, while that person is fixed on 
the object, there appears in the field of vision 
F = fixation point 
A = second object in field 
AR = projection of image of right eye") crossed 
AL = projection of image of left eye J diplopia 
M = macula 
Figure 4-31. 
another object nearer than the object fixed 
upon, diplopia occurs due to the fact that the 
image of the nearer object falls to the temporal 
side of each macula. Since these areas are not 
corresponding, fusion cannot take place and a 
crossed diplopia occurs. The sensation of 
crossed diplopia, although suppressed from a 
point of view of attention, stimulates a cere- 
bral level sensation of nearness of the second 
object in the field. 
F = fixation point 
A = second object in field 
AR = projection of image of right eye") homonomous 
AL =projection of image of left eyej diplopia 
M = macula 
Figure 4-32. 
77 AVIATION MEDICINE PRACTICE 
The converse takes place for a more distant 
object looming into the visual field. The diplopia 
is homonomous and gives rise to the impres- 
sion of greater distance than the object fixed 
upon. In this case the two nasal fields are 
stimulated. 
Binocular parallax.—Binocular parallax has 
been accomplished when each of two objects 
in a field of vision stimulate exactly correspond- 
ing points in the retina. A little study of the 
following diagram will indicate that this situa- 
tion can exist mathematically only when the 
two objects in the field fit certain conditions. 
points Ar and AL are mathematically cor- 
responding points. 
Note that line A-AL and line FMR are paral- 
lel in the diagram. They were made so pur- 
posely in order to help explain the principles 
upon which a well-known depth perception 
test is based. When point A is the same dis- 
tance from point F as the person’s interpupil- 
lary distance, the angle AL AAI{ will equal 
angle MLFMR. This will give rise to the im- 
pression that A and F are the same distance 
from the eyes. 
The term binocular parallax has been coined 
to describe this condition. But more broadly, 
binocular parallax exists whenever angle 
ANrF for the right eye equals angle ANLF. 
This can occur only when A is on the Vieth- 
Meuller circle for F, 
If you can bear up under this dull reading 
for a little longer, we think the fog around this 
discussion will clear. 
That part of the Vieth-Meuller circle which 
lies outside the eyes is called the horoptor. You 
will note that, mathematically speaking, as soon 
as A leaves the horoptor the angles at the nodal 
points of the eyes will no longer be equal and 
stimulation of corresponding points would be 
impossible. In fact it should be clear to you 
from previous discussion that physiological di- 
plopia should, according to the diagram, occur 
as soon as A is moved off the horoptor. 
It is obvious that as point F is moved out, or 
as the eye fixes on an object further and further 
away, the Vieth-Meuller circle becomes larger 
and the horoptor, therefore, flatter. Again from 
a mathematical standpoint when F, the point 
fixation, is at infinity the horoptor should be a 
straight line. 
Our diagram permits all these mathematical 
facts to be stated quite readily. There is only 
one thing the matter—the visual system does 
not work that way. As a matter of fact, ex- 
periment has shown that physiologically speak- 
ing, as opposed to mathematical diagrams, the 
horoptor of the human eye becomes straight 
and flat at a distance of little over an arm’s 
length. The functional corresponding units of 
the retina are not corresponding points but 
corresponding areas. As long as an object 
throws an image into each eye in such a manner 
as to stimulate corresponding areas no diplopia 
Fs fixation point 
NR = nodal point right *y« 
NL = nodal point loft ey« 
MR= macula right ey« 
ML = macula left eye 
AR and ALZ corresponding 
points 
Figure 4-33. 
The small circle passes through the nodal 
points of both eyes and also the point of fixa- 
tion. Any circle which fulfills these specifica- 
tions is called a Vieth-Meuller circle. A second 
or larger circle is drawn simply to indicate 
than an infinite number of Vieth-Meuller circles 
exist for any pair of eyes. Each time the eyes 
focus on a particular object a Vieth-Meuller 
circle is formed for that particular point of 
fixation. 
Let us consider the eyes as converging on 
F. Each eye has point F, the nodal point and 
its macula in line. 
Now point A is brought into the field. If 
point A happens to be on the Vieth-Meuller 
circle the angles indicated at the nodal point 
of each eye will be equal for they will both 
be subtended by the same arc—AF. It will 
follow therefore that, under those conditions, 
the arc MA,„ will equal arc MAR therefore, 
78 Chapter 4. — OPHTHALMOLOGY IN AVIATION MEDICINE 
occurs and the individual concerned develops 
the concept that the “off fixation” object caus- 
ing that stimulation is the same distance from 
the eyes as is the point of fixation. When this 
physiological phenomena exists the eyes are 
said to be in binocular parallax. 
The discrepancy between the mathematics 
of our diagram and the physiological facts 
might be further appreciated by the comment 
that the corresponding areas widen; that is, 
become less definite in the areas of the retina 
for off the macula. That is why we can get a 
much more accurate conception of depth for 
objects in the field of vision immediately 
around the object fixed upon. 
This same widening of corresponding areas 
makes it necessary for us to make further ad- 
justment of our mathematical principles to fit 
the areas immediately in front and behind the 
horoptor. We have already indicated that, 
mathematically speaking, as soon as an object 
falls forward or behind the horoptor physiologi- 
cal diplopia should occur. However, when we 
consider that the retinal units are correspond- 
ing areas and not corresponding points, it is 
easier to appreciate that there is an area in 
front and behind the sharp line of the horoptor 
in which objects do not produce the sensation 
of diplopia. That area too widens as we leave 
the point of fixation. This area is called Pa- 
num’s fusion area and is diagramed as follows: 
directly on the horoptor. This sensation of 
depth which results from the “pull” of stereo- 
scopic vision is very accurate for short dis- 
tances. Beyond 2 meters stereoscopic vision 
rapidly loses its effectiveness as a cue to depth. 
Figure 4-35.—The Howard-Dolman apparatus. 
The Howard-Dolman apparatus is now used 
as a test for depth perception by both the Navy 
and the Air Force. The apparatus is designed 
to eliminate all cues of depth perception but 
physiological diplopia, binocular parallax, and 
sterocopic vision. The designers of the ap- 
paratus assumed that a person who could dem- 
onstrate proper use of these three faculties, 
which they called basic, could be considered 
safe to fly. They also assumed that failure to 
demonstrate proficiency in the use of these 
faculties must be considered as evidence that 
the person could not develop sufficient concep- 
tion of depth to be termed safe for flying. 
The Howard-Dolman apparatus consists of a 
fixed rod and a movable rod. The movable rod 
is placed on a slide which keeps it in a plane 
64 mm. from the fixed rod. This distance was 
chosen because it is the average interpupillary 
distance of Americans. 
If you look again at figure 4-35 you will note 
that the rod on the right (F) might be con- 
sidered to be the fixed rod, while the rod on 
the left (A), the adjustable rod, may be moved 
by the examinee by manipulation of the strings. 
When (A) is a considerable distance in front or 
behind (F), the examinee receives depth cues by 
physiological diplopia. If the examinee has the 
ability to use binocular parallax he will stop the 
movement at such a point as to place the mov- 
H - H' = Horoptor 
Shaded area in Pannum’s fusion area 
Figure 4-34. 
Objects which lie within Panum’s fusion area 
give rise to the stereoscopic vision because they 
are fused. The sensation of the pull to maintain 
this fusion allows us to interpret this stereo- 
scopic phenomena in terms of depth. By this 
we mean that fusion of an object just inside 
the forward or backward edge of Panum’s 
fusion area will cause a sensation of pull to 
preserve fusion much greater than that neces- 
sary to preserve fusion when the object is 
79 AVIATION MEDICINE PRACTICE 
able rod exactly opposite the fixed rod. This is 
assuming that the examinee has an interpupil- 
lary distance of exactly 64 mm. For those who 
have a greater or smaller interpupillary dis- 
tance, the binocular parallax cue is slightly less 
accurate. For this reason an allowance is made 
in the standard for passing this test. The candi- 
date passes if the average of five trials gives 
less than 30 mm. separation between the fixed 
and movable rods. 
Care must be taken not to permit the candi- 
date to swing his head from side to side and 
thus get cues from motion parallax. He must 
not be allowed to swing strings from one ex- 
treme stop to the other. The candidate should 
be instructed to drop the strings out of his 
hand after each trial. Finally, the examiner 
must maintain a “poker face” lest the candi- 
date get information from the examiner’s ex- 
pressions of approval or disapproval. 
There has been much criticism of the How- 
ard-Dolman apparatus in recent years. Re- 
search reports have been made which indicate 
that it has a low coefficient of reliability and 
validity. This discrepancy of the apparatus 
is now generally accepted but up to the present 
no other apparatus has been developed as a 
practical substitute. The criticism of the How- 
ard-Dolman apparatus is based on reliable 
statistics which indicate that the apparatus 
does not show the same findings for the same 
man on retest. Furthermore, a series of tests 
run on successful college athletes, whom the 
tester claims must have had good depth percep- 
tion, showed that a larger percentage of these 
athletes failed the test than occurs in a normal 
population. 
Those who wish to defend the use of the 
apparatus feel that it still has clinical value. 
It is an easy test to perform and the test can 
be done by any well trained technician. Those 
who fail to attain an average of 30 mm. or 
less difference in 5 trials should at least be 
subjected to a more careful visual analysis 
before it is assumed that the apparatus is about 
to disqualify a normal candidate. In this man- 
figure 4-36.—Front and rear view of the Verhoff Depth perception 
80 Chapter 4. — OPHTHALMOLOGY IN AVIATION MEDICINE 
ner the test acts as a screen for singling out 
persons who need a more careful physical 
check. If the test by its inaccuracy lets through 
persons with poor depth perception, that fact 
is regrettable. Obviously, surrendering the test 
would not change this situation. All these 
points must be considered by the Air Force and 
Navy committees on physical standards before 
a change in present directives are made. For 
the present we must use the Howard-Dolman 
apparatus as directed. Any flight surgeon who 
feels he is doing an injustice to a candidate, 
by failing him solely because of the Howard- 
Dolman test report, might well make a full 
report of the case and request that the Bureau 
of Medicine and Surgery give the case special 
attention and a final decision. 
The Verhoff depth perception is now being 
studied as a possible replacement for the How- 
ard-Dolman apparatus. It consists of a small 
box so arranged as to place before the examinee 
a series of variations of three upright rods. 
One of the three rods is always in front or be- 
hind the other two. The thickness of each rod 
is different in order to prevent the examinee 
from using the size of the image as a cue. The 
apparatus permits eight different relations of 
the rods to each other the test box is held at 1 
meter from the examinee. All eight positions 
must be called correctly. Stereoscopic vision 
will be the examinee’s only cue. If it can be 
proven that a person with good stereoscopic 
vision can be considered to have sufficient depth 
perception to safely fly an aeroplane, this ap- 
paratus may replace the Howard-Dolman ap- 
paratus. 
REVIEW QUESTIONS 
1. What is physiological diplopia? 
2. Name three factors which contribute to depth 
perception of a one-eyed person. 
3. What factors contributing to depth perception 
are only possible when binocular vision is enjoyed? 
4. What is the Vieth-Mueller Circle? 
5. What is the horoptor? 
6. What is Panum’s fusion area 
7. Why is depth perception so important in aviation? 
8. If you forget the effect of motion parallax how 
can you quickly remind yourself about it? 
9. Name all the factors which aid in the estimation 
of depth. 
COLOR VISION 
When color vision of certain persons differs 
from that of the normal, these persons are 
said to be color blind. This is an unfortunate 
term for it implies that they are blind to all 
color and that all such persons have the same 
color perception. Neither of these implications 
has any basis in fact. The color-blind may be 
understood to include all those persons whose 
color vision is different from that of the normal 
and whose perception of color is, in general, 
more limited. They may be divided at once into 
two classes—the congenital and the acquired. 
We will not consider acquired color-blindness 
for this type is uncommon in the aviation age 
group; moreover, in these cases the defective 
color vision results from grave intoxication or 
is but part—usually a minor part—of a serious 
ocular or nurological disorder. 
Congenital color-blindness is a developmental 
defect. It almost always affects both eyes. The 
other ocular functions are not affected. It is 
hereditary and tends to be transmitted through 
the females and to be manifest in the males. 
The condition cannot be corrected or even im- 
proved, though the color-blind do learn to con- 
ceal the defect. They are frequently ignorant 
of the defect themselves. 
It is estimated that about 80 percent of the 
population have normal color vision. Of the 
remaining 20 percent, a considerable propor- 
tion are in the group who have acquired color- 
blindness. Congenital color-blindness of some 
degree occurs in from 8.5 to 10 percent of men 
and 2 percent of women. Color blindness of 
such as to be disqualifying in occupations 
requiring color discriminations occurs in ap- 
proximately 3.5 percent of men and 0.7 percent 
of women. It is this 3.5 percent of the can- 
didates for commission with whom we are con- 
cerned, but in examining applicants for flight 
training, effort must be made to eliminate the 
entire group (8.5 to 10 percent) with subnormal 
color perception. 
Trichromatic or normal color vision is char- 
acterized by the following: 
1. The spectrum of a glowing solid presents 
uninterrupted series of hues from red of about 
760 to the violet of, say 380 n. 
2. There are no black, gray, or white areas 
or bands in this series. 
81 AVIATION MEDICINE PRACTICE 
3. In this spectrum the individual is able 
to recognize a large number of hues and clearly 
differentiates between the six or seven ordinary 
hues of red, orange, yellow, green, blue, indigo 
and violet. The ability to distinguish hues and 
colors is largely a matter of training; artists 
are superior in this respect and, as a rule, 
orientals also have a keener appreciation of 
colors. 
4. Another characteristic feature of normal 
color vision is the fact that all colors with their 
almost infinite variety of hue, intensity, and 
saturation can be produced by the mixing in 
the proper proportions of three colors. These 
three spectral colors are red, green and blue 
and are known as the fundamental or primary 
colors. If we should take any two of these 
three colors and mix them in various propor- 
tions, certain colors which the normal individual 
is able to discern, cannot be produced as all 
three color wave lengths must be employed 
in order to produce all possible color sensations. 
For this reason normal color vision is known 
as trichromatic color vision. 
There are two types of defective color per- 
ception with which we are concerned: dis- 
chromic and monochromic color perception. 
Both are disqualifying and the latter is much 
more difficult to detect. The dichromat sees only 
two of the fundamental colors and as for the 
trichomatic or normal individual, three are 
necessary to produce all hues in the spectrum. 
It is evident that the dichromat lacks power 
to be properly stimulated by one of these three. 
Now this may be red, green, or blue light. In 
conformity to this, we speak of red blindness, 
green blindness, and blue blindness; or in tech- 
nical terms, protanopia, deuteranopia, and tri- 
tanopia, respectively. These are named in order 
of their frequency of occurrence. Tritanopia 
is very rare, and is usually caused by disease 
and detachment of the retina. It is believed 
that the dichromat spectrum has a neutral band 
of white or gray and the exact location of this 
band divides the dichromats into three groups, 
i.e.: protanopes (492 /x), deuteranopes (502 /x), 
tritanopes (570 n). 
There are many forms of color vision which 
connect the normal tricromatic with dichro- 
matic vision. While these individuals recog- 
nize three fundamental colors, there exists a 
certain amount of difference between them and 
the true trichromats. This is generally referred 
to as anomalous trichromatic vision, or ab- 
normal trichromatopia and is sometimes divided 
into protanomals and deuteranomals (partial or 
anomalous). 
Stress is placed on detection of color blind- 
ness in prospective military aviators by rea- 
son of the requirements: (a) recognition of 
various luminous signals such as boundary 
lights, obstruction lights, navigating lights, 
and rocket signals. Distinctive colors are em- 
ployed to signify various vital conditions and 
prompt comprehension is essential, (b) Recog- 
nition of colored flags and other daytime signal 
ing devices, (c) Ability to discriminate between 
various conditions of terrain by colors thereof. 
For example: shades of green of pasture and 
short grass for a possible safe landing com- 
pared to a different shade of green in an ad- 
jacent area indicating a soft boggy marsh; 
shades of brown of a plowed field with soft, 
dangerous surface compared to a slightly dif- 
ferent shade of brown indicating a field of 
dried grass or short, dry weeds which may 
prove to be a place to put the wheels down. 
In a forced landing there is little time to 
make a choice and a second choice is impos- 
sible after altitude is lost. Rain, light fog, and 
a cloudy condition, especially in the early morn- 
ing or toward evening, render color discrimina- 
tion from an altitude very difficult for the 
normal eye and supremely hazardous for the 
individual with inadequate color discrimination 
and may easily end in disaster. 
It has been found that individuals with de- 
fective color vision, even almost approaching 
normal, when excited or nervous frequently 
suffer reduction in color discrimination. A tri- 
chromat may be reduced to a dicromat and 
mistake a green light for a red one and vice 
versa. 
Many theories have been and still are being 
formulated to explain trichromatism and the 
aberrations of the color blind, but so far, none 
have proven entirely satisfactory. Some of the 
more common theories are: Young-Helmhotz 
physical theory of three sets of nerves or 
cones; Hering psychological theory of three 
photochemical substances anterior to the cor- 
tex ; and Ladd-Franklin theory on evolution 
82 Chapter 4. — OPHTHALMOLOGY IN AVIATION MEDICINE 
stating that the primitive man perceived only 
black and white. 
The Ishihara test is very effective for color 
vision testing provided the examinee has not 
had an opportunity to study the plates. Many 
of them have done so. Hence, it is necessary 
for the examiner to have a degree of suspicion, 
especially in “re-examination” cases when us- 
ing this test. Familiarity with the test is to 
be expected when (1) the plates with alterna- 
tive readings are read with greater facility 
than are the plates with one reading, (2) 
greater difficulty is experienced in tracing the 
line plates than reading any of the plates, (8) 
there is any indication that the numerals do 
not stand out in bold relief as they do to the 
normal. 
The advantages of the Ishihara over other 
tests are that it is rapid (li/£ to 2 minutes) and 
will disclose practically all cases of significant 
abnormality of color preception and that it 
will never lead to a diagnosis of color blindness 
in a normal individual or in one who is not 
disqualified by regulations. Stillings pseudo- 
isochromatic plates are similar to the Ishihara. 
Because of the larger number of plates, it is 
more difficult for an individual with defective 
color vision to familiarize himself with them 
and, even if he has done so, the results of this 
study can be largely nulified by the simple 
expedient of turning the book upside down. 
If the plates are read in the same way with 
the same ease that the normal read them— 
record “normal.” If there is any evidence that 
the plates do not afford normal contrast or, 
because of discrepancies previously referred to, 
it seems probably that the candidate has stud- 
ied the plates, a detailed record is made of the 
readings and the examination is then continued 
with another test. The Edridge-Green lamp or 
the S6-690 lantern is frequently used as a 
secondary test and the results of which should 
be reported in addition to the plate readings 
when reporting a deficiency in color vision to 
BuMed. The lantern is done at 10 feet with 
2 mm. aperture. Correct recognition of white, 
green, and red lights is required both when 
clear and when fogged. A new test lantern 
for colors has been developed by the Navy. It 
will probably replace the Edridge-Green lantern 
in the near future. 
A summary of the Bureau of Medicine and 
Surgery “Color Perception Standards” and 
technique in using the pseudo-isochromatic 
plates which is given in mimeograph form to 
all classes of flight surgeons follows. For com- 
plete standards refer to BuMed Manual, par. 
2125. 
COLOR PERCEPTION STANDARDS 
SUMMARY OF BUMED CIRCULAR LETTER 46-177 
Device—American Optical Company Pseudo- 
isochromatic Plates 
Note—DO NOT LEAVE THESE INSTRUCTIONS 
AROUND WHERE PROSPECTIVE CANDIDATES 
CAN MEMORIZE THE PLATES WHICH THE 
NAVY USES. 
Technique. 
1. Use Macbeth Lamp or equivalent. 
2. Distance—Place plates 21/2 feet from 
applicant’s eyes. 
3. Three seconds to read each plate. 
4. Applicant told “Read the numbers.” 
a. Show No. 25 (demonstration plate) 
first. 
b. Show the 18 “number” plates in any 
order you wish. 
Do not allow candidate to tilt, face 
or fuss into different angles of as- 
pect. 
5. “Line Tracing” Charts. 
a. First show demonstration plate No. 
46. 
b. Have applicant trace No. 35 and 
No. 36. 
Do not allow candidate to touch 
plates with his fingers—have him 
use a glass rod or rubber eraser on 
a pencil. The use of fingers will 
soon stain and destroy the plates. 
Plates to be used. 
Plate 
Normal 
Plate 
Normal 
Plate 
Normal 
No. 
Reading 
No. 
Reading 
No. 
Reading 
6 
6 
12 
97 
36 
follow 
8 
42 
23 
56 
40 
65 
9 
56 
24 
27 
41 
15 
10 
27 
25* 
12 
42 
74 
12 
57 
27 
89 
43 
47 
14 
75 
29 
86 
44 
98 
19 
5 
35 
follow 
46* 
follow 
20 
3 
* Demonstration Plates. 
83 AVIATION MEDICINE PRACTICE 
Standard 
Must have 
17 correct..... 
Candidates for 
Warrant Officers 
Commissioned Officers 
Nurse 
Naval Academy 
Naval Aviators 
Student Naval Aviators 
Enlisted men for special 
rates (such as signal- 
man, electrician, etc.) 
It is quite impossible for an individual to 
check these characteristics. Therefore, sunglass- 
es should be bought from a reliable manufac- 
turer who will guarantee that his particular 
glasses will keep out most of the infra-red and 
ultraviolet light. Furthermore, they should 
state that the lenses do not exclude more than 
30 percent of any portion of the visual spec- 
trum. Bausch and Bomb’s “rayban” or Ameri- 
can Optical Company’s “kalobar” glasses will 
meet these specifications. They both have a 
greenish tint. If a manufacturer can make a 
blue tinted glass which will accomplish as good 
results, these too will be satisfactory. The 
color of the glass is not important. 
If a pilot has any refractive error greater 
than i/4-diopter, it is most satisfactory to have 
his correction ground into his sunglasses. This 
can be done without too great expense. 
When a pilot wears his sunglasses in the 
office, the wise flight surgeon will watch him 
closely. He may be hiding bloodshot eyes which 
are, in the absence of infection, an indication 
of unwisely spent nights. Anyone who claims 
photophalia under artificial light has either 
pathology or a very sensitive personality. In 
the latter case, it is well for the flight surgeon 
to take note of that fact. 
When a pilot who is wearing sunglasses 
wishes to see better, he must take them off. 
This should always be done before landing on 
a smooth runway or smooth water. The best 
sunglasses will disturb perception. 
Blackout.—The deficiancy in retinal function 
in relation to acceleration and deceleration is 
more properly discussed in the portion of the 
course dealing with aviation safety. The re- 
tina is the first nuerosensory mechanism to fail 
as the body is subjected to negative “G.” 
The problem of avoiding these blackouts is 
more properly one of aviation physiology and 
aviation safety. 
Anoxia.—Anoxia is another problem which is 
of considerable interest to the ophthalmologist 
in so far as visual efficiency decreases in every 
respect as the pilot passes into the early stages 
of anoxia. Resolving power diminishes and 
phorias increase, but the subject of the anoxia 
seldom recognizes his inadequacies. The treat- 
ment is not a problem for the opthalmologist 
OPHTHALMOLOGICAL PROBLEMS 
OF AVIATION 
Protecting eyes.—Until recently one of the 
greatest eye problems in aviation has been the 
selection of a goggle which would offer maxi- 
mum vision and maximum protection. The gog- 
gle problem has faded out in view of the mod- 
ern plane and its closed cockpit. We do not 
mean to insinuate that goggles are no longer 
needed in aviation but it is doubted whether 
they are important enough now to call forth 
any change in the very fine, one piece, sponge 
rubber framed goggle which was developed 
during the past war. 
Sunshades of some form are still a definite 
necessity under some flight conditions. Any- 
one who has flown “on top” for any length of 
time is well aware that the glare from the 
white cloud masses will cause at least tiring 
and inefficiency if not permanent damage to 
the eye. 
Aviators frequently ask the flights surgeon 
to advise them as to what is the best type 
sun glasses. Should they be brown, rose, green, 
or blue? Sun glasses are worn by aviators for 
several reasons. First, they protect the cornea 
from the heat of infra-red rays; secondly, 
they protect the conjunctiva and corneal 
epithelium from ultraviolet radiation which cer- 
tainly causes temporary irritation; and finally, 
they suppress the tiring and annoying bright- 
ness of the background either in flying over 
clouds or over snow. One must avoid, of course, 
poorly polished glasses with astigmatic errors 
which will be disturbing and reduce visual acu- 
ity. Finally, we want, if possible, a glass which 
will not markedly intercept any particular 
color. 
84 Chapter 4. — OPHTHALMOLOGY IN AVIATION MEDICINE 
for it involves treating the anoxia or better— 
avoiding anoxia. 
Night vision.—The ability to see at night 
is of supreme importance to the combat aviator. 
The retina, you will recall, has two types of 
neurosensory endings. They may be differen- 
tiated histologically by their shape. One type 
is long and narrow cystoplasmic formations 
called rods: the other type is relatively shorter 
and wider at the base and narrows down ab- 
ruptly to a point. This shape has prompted 
the name—cone. Though these nerve endings 
are named according to their shape, they are 
most important because of their functions. The 
cones are concerned with photoptic vision or 
vision in adequate light. They are massed most- 
ly in the area of the macula where there are 
no rods at all. As we pass off the macula area 
the rods appear abruptly and in great numbers 
but the cones become relatively few in number. 
Cones are scattered throughout the entire re- 
tinal areas but their relative number in com- 
parison to rods diminishes rapidly as we pass 
toward the periphery of the retina. A very 
short exposure to daylight makes the rod end- 
ings insensitive to further stimulation. They 
remain insensitive until the eye is allowed to re- 
main in the dark for a considerable period of 
time. No drug has so far been discovered, no 
food can be taken, which will cause rods to 
hold their sensitivity or restore their sensi- 
tivity, once lost. The only manner by which this 
can be accomplished is to keep the eye in the 
dark for a certain period of time. Physiological 
rejuvination of the rods is then accomplished. 
At very low levels of illumination—levels 
much too low to permit stimulation of the 
cones of the retina—the sensitivity of the rods 
is retained. The resolving power of the rod 
endings of the retina is very low. For this 
reason, it is impossible for the human eye to 
attain the minute details in dim light which 
is possible under photoptic or bright light con- 
ditions. It is impossible to express in terms 
of candle power where the cones give up and 
the rods take over the visual stimulus. The 
effect is not an abrupt one but rather one of 
transition. From a practical point of view, we 
might state that any degree of light from the 
darkest blackness of a cloud-filled sky at night, 
through the starlight and the light of a dim 
moon to the light of a full moon on a clear 
night must be considered the light intensities 
through which the rods function. As we raise 
the intensity above the light of a bright moon 
the cones begin to come in and the rods begin 
to fail. The brighter the light, the more rapid 
the failure of the rod cells. 
There appears to be little variance in the 
degree of sensitivity to scotopic conditions 
among healthy humans. You either have it or 
you don’t have it. As has been said, no form 
of therapy will revive rod-cell vision to one who 
does not have it. As far we know there is no 
such thing as functional night blindness. People 
suffering from retinitis pigmentosa, lues, and 
other diseases lose their scotopic vision tem- 
porarily or permanently but we have heard of 
no true congenital night blindness. Physiologi- 
cal night blindness does occur whenever a per- 
son is exposed to any bright portion of the 
spectrum above the level of red. 
With these facts in mind the problem of 
increasing a flyer’s visual efficiency at night 
becomes one of training. This is started early 
in the career of an aviator and effort is made 
to teach student aviators: 
1. How to preserve the sensitivity of their 
rod elements. 
2. How to best employ the elements so 
preserved. 
A special course of instruction is part of the 
syllabus of all Navy and Air Force student 
aviators. 
The class is brought in from ordinary day- 
light to what appears to be a room of complete 
darkness. There is, however, at the time the 
students enter the room, a group of landscape 
silhouettes cast on the front wall of the lecture 
room by means of a very dim light. 
While the students sit in through apparent 
complete darkness, the instructor explains 
roughly the physiology of the retina. He calls at- 
tention to the students that the macula which 
contains no rod elements is completely blind 
to dim light. As the students listen, the rod 
elements which were inactive when they en- 
tered the dark room, gradually regain their 
sensitivity. The instructor calls for any student 
who sees any object on the way to speak up. 
The instructor now suggests that students will 
see more clearly in dim light if they will look, 
85 AVIATION MEDICINE PRACTICE 
not directly at the object of interest, but slight- 
ly off to the side. This, the students find, does 
work. They find that by scanning the simulated 
horizons before them that they pick up smaller 
and more difficult silhouettes with their off- 
center or peripheral vision. 
Each student is now asked to close one eye 
tightly and cover it with his hand. The full 
lights are switched on for about one minute. 
The silhouettes disappear. The lights are 
switched off again and the student sees for 
himself that the eye which was covered is able 
to see the silhouettes as before but the eye 
exposed to the bright light is blind. Therefore, 
the flyer is advised that if he must use white 
light to read a map at night he must do so 
with one eye only, then at least one eye will 
remain dark-adapted. 
The students now put on red goggles. The 
lights are switched on for a minute: they are 
told to keep their eyes open. Again the lights 
are switched off and the red goggles removed. 
The student finds by actual experience that 
a red light will not disturb his night vision. 
The instructor now sums up the lesson. He 
advises student pilots that before they take-off 
at night they must dark-adapt their eyes by 
sitting in complete darkness for about 30 min- 
utes. This period can be shortened to 10 min- 
utes if red lenses have been worn for at least 
20 minutes before entering complete darkness. 
Once dark-adapted, the flyer must not allow 
his eyes to be exposed to any but very dim 
light. If he must read it must be done in red 
light. Incidentally, he is advised not to try 
to read red print in a red light for he can’t 
see it. 
This vivid practical experience convinces the 
future pilot that there is a right way and wrong 
way to prepare for night flying. However, ex- 
perience has proven that the flight surgeon 
should frequently “brief” his squadron on this 
subject to refresh their memories—especially 
when night flying is only infrequently per- 
formed. 
BIBLIOGRAPHY 
Title 
Diseases of the 
Author 
Publisher 
Eye 
The Eye and 
.. May 
. Wm. Wood 
Baltimore, Md. 
Its Diseases.... 
Textbook of 
.Saunders Company 
Philadelphia, Pa. 
Ophthalmology. 
Introduction to 
.. Gifford 
•Saunders Company 
Philadelphia, Pa. 
Ophthalmology. 
Methods of 
.. Kronfeed 
• Chas. A. Thomas 
Baltimore, Md. 
Refraction 
Textbook of 
Ophthalmology 
.. Thorington 
.Blakiston 
Philadelphia, Pa. 
(3 Volumes) ... 
Outline of Ocular 
. . Duke Elder 
.C. V. Mosby Company 
St. Louis, Mo. 
Refraction 
.. Maxwell 
.Medical Pub. Company 
Medical Arts Building 
Principles and 
Practice of 
Omaha, Nebraska 
Perimetry 
Anatomy of the 
,. .Peter 
. Lea Febiger 
Philadelphia, Pa. 
Eye and Orbit. 
Extra Ocular 
.. .Wolff 
, Blakiston 
Philadelphia, Pa. 
Muscles 
Atlas Fundi 
, Lea Febiger 
Philadelphia, Pa. 
Oculi 
Internal Diseases 
Macmillan Company 
New York, N. Y. 
of the Eye 
Surgery of the 
.F. A. Davis 
Philadelphia, Pa. 
Eye 
.. Wilmer & Alvis. 
.Saunders Company 
Philadelphia, Pa. 
Pectorial Survey of Business Letter 
Military Optics. 
The Human Eye 
in Anatomical 
. .Service 
.McGraw Hill Company 
New York City, N. Y, 
Transparecies.. 
The Ocularotary 
. .McHugh, Gladys.Bausch & Lomb Press 
Rochester, N. Y. 
Muscles 
.The Cumosby Company 
St. Louis, Mo. 
86 CHAPTER 5 
OTOLARYNGOLOGY IN AVIATION MEDICINE* 
Abnormal conditions of the ear, nose, and 
throat assume greater importance when deal- 
ing with flying personnel. A man working on 
the ground may be only slightly troubled with 
a moderate congestion of the nasal mucous 
membrane whereas an aviator at extreme alti- 
tudes could be incapacitated with a similar con- 
dition. 
The following chapter is a brief discussion 
of otolaryngology, and is limited to the ele- 
mentary principles as they pertain to the study 
of aviation medicine. 
ANATOMY OF THE EAR 
The external ear.—The external ear is that 
part of the auditory apparatus located laterally 
to the tympanic membrane. It consists of the 
auricle and the external auditory canal. The 
latter is divided into cartilagino-membranous 
and bony portions. 
The auricle is an oblong, flat, molded struc- 
ture consisting of skin covering a skeletal 
framework of elastic cartilage. The auricle 
differs in size and shape in different individuals 
but both ears usually are symmetrical. The 
landmarks include the helix, antihelix, tragus, 
antigragus, concha, lobule, incisura inter- 
tragica, auricular fossa, and the cavity of the 
concha leading to the meatus of the external 
auditory canal. The cartilage of the auricle is 
continuous with that of the canal except above 
and anteriorly where it is completed by a tough 
fibrous membrane extending between the tragus 
and the commencement of the helix. 
Nerve supply.—The sensory nerves of the 
auricle are branches of the great auricular and 
lesser occipital nerves from the cervical plexus, 
and the auriculotemporal branch of the man- 
dibular division of the fifth nerve. The posterior 
internal part of the external auditory canal is 
innervated by a branch of the vagus (Arnolds 
nerve). Stimulation of this auricular branch 
of the vagus is responsible for the cough reflex 
during instrumentation of the external audi- 
tory canal. 
Blood supply.—The blood supply of the ex- 
ternal ear is by twigs from the neighboring 
superficial temporal and posterior auricular ar- 
teries which are branches of the external caro- 
tid artery. The veins are branches of the facial 
and temporal and the posterior auricular veins. 
The latter sometimes join the transverse sinus 
through the mastoid emmissary vein. 
Lymphatics and nodes.—The abundant lym- 
phatic plexus of the auricle empties into the 
preauricular, post-auricular and inferior auricu- 
lar lymph nodes. These in turn empty into the 
upper deep cervical nodes. 
THE EXTERNAL AUDITORY CANAL 
The external canal consists of cartilagino- 
membranous and bony parts. It is about 1*4 
inches in length. The cartilaginous part forms 
about one-third of the entire length, its direc- 
tion being upward and backward. The outer 
orifice of the canal is elliptical with its greatest 
diameter directed from the above downward. 
In its lower anterior wall are several fissures 
in the cartilage, the incisurae Santorini, which 
allow for flexibility of the canal. 
The bony canal fuses laterally with the car- 
tilaginous portion, forming two-thirds of the 
entire length of the canal. Its direction is 
downward, inward, and forward, forming an 
angle with the junction of the cartilaginous 
portion. 
Histology.—The epidermal lining of the ex- 
ternal canal is a continuation of the integu- 
* Prepared by Cdr. D. G. MacKinnon, (MC) USN. 
87 AVIATION MEDICINE PRACTICE 
Figure 5-1. 
ment of the auricle. The membranocartilagin- 
ous portion contains hair follicles, sebaceous 
and ceruminous glands. These are absent in 
the bony portion. The skin of the canal is 
tightly adherent to the periosteum, with almost 
no intervening connective tissue layer. 
THE MIDDLE EAR 
The middle ear contains the mechanism for 
the conduction of sound waves to the internal 
ear. It consists of a series of pneumatic spaces 
which include the Eustachian tube, the middle 
ear cavity itself and the pneumatic cells of the 
mastoid process. The cavity of the middle ear 
is best described as a six-sided box measuring 
15 mm. from above downward and from front 
to back. Laterally, it is much narrower, meas- 
uring about 4 mm. from side to side near the 
top, even less than that near the center and 
then widening a bit near the bottom. 
The lateral wall of the middle ear is partly 
bony and partly membranous. The membran- 
ous portion (the tympanic membrane) closes the 
middle ear cavity from the external auditory 
canal. The membrane is inserted in a groove in 
the tympanic bone by a circular ligament called 
the annulus tympanicus. The membrane is 
roughly circular, being about 8 mm. wide and 
9 mm. high. It is about one-tenth of a millimeter 
in thickness and is made up of three layers. 
The outer layer or lateral layer is a continuation 
of the epidermal lining of the canal; the inner 
layer is a continuation of the mucous mem- 
brane lining the middle ear cavity. The middle 
layer consists of connective tissue fibers, both 
88 Chapter 5. — OTOLARYNGOLOGY IN AVIATION MEDICINE 
Fig. HO. The normal tympanic mem- 
brane (right side! with its topographic 
and clinical representation. The division 
into quadrants is essential (or descriptive 
purposes and the knowledge of topogra- 
phy for the clinical significance of the 
site of a perforation of the tympanic mem- 
brane. I he shadow of the round w indow 
may he seen through a translucent mem- 
brane. Processus cochieariformis is desig- 
nated by Proc. cochleans. 
Figure 5-2. 
circular and radial which are attached peri- 
pherically to the margins of the bony ring and 
centrally are inserted into the handle and short 
process of the malleus. This middle layer is 
relatively heavy (pars tensa) except for a small 
triangular area above the short process of the 
handle of the malleus, lying in a niche in the 
superior wall of the canal. This part of the 
tympanic membrane is called Shrapnell’s mem- 
brane or the pars flaccida. 
The lateral surface of the tympanic mem- 
brane.—The most depressed point of the tym- 
panic membrane is located slightly posterior 
and inferior to its center. This corresponds to 
the tip of the handle of the malleus and is 
termed the umbo. From here a whitish streak, 
the handle of the malleus, extends upward and 
forward to the superior margin, to end in a 
slight projection, the short process of the 
handle of the malleus. From the short process 
two small ligaments extend to the edges of 
the notch of Rivinius, forming the anterior 
and posterior folds. These folds enclose that 
part of the tympanic membrane called Shrap- 
nell’s membrane. The cone of light is formed 
by reflection of concentrated rays of light from 
the surface of the membrane. It is normally 
found in the anterior, inferior quadrant, is tri- 
angular in shape with the apex of the narrow 
cone at the umbo. 
The blood supply to the tympanic membrane 
is derived chiefly from the deep auricular 
branch of the internal maxillary artery. The 
blood vessels lie chiefly with nerve fibers in 
Shrapnell’s membrane, along the posterior mar- 
gin of the handle of the malleus and just on 
the margin of the pars tensa. The mucous sur- 
face is supplied by twigs from the internal 
maxillary and the posterior auricular arteries. 
The two sets of arteries, one on either side 
89 AVIATION MEDICINE PRACTICE 
of the membrane, connect through anasto- 
moses. The nerve supply to the membrane is 
from the trigeminal, glossopharyngeal and 
vagus nerves. The areas supplied by each have 
not been accurately determined. 
Superior wall.—The superior surface, or teg- 
men, or roof, varies in thickness from 3 or 
4 mm. to that of thin paper. It separates the 
middle cranial fossa from the middle ear cavity. 
It is a favorable site for extension of middle 
ear infections and fractures. 
Inferior wall.—The floor or hypotympanum 
is a thin, bony structure separating the hypo- 
tympanum from the jugular bulb. The bulb 
may mound into the middle ear cavity and 
there may be dehiscences in the bony cover- 
ing. This possibility should be kept in mind 
whenever a myringotomy is being done, as seri- 
ous hemorrhage may result. 
Medial wall.—The medial or labyrinthine 
wall is also the lateral wall of the inner ear. 
It contains several important structures and 
niches including the horizontal semicircular 
canal, the facial canal, the oval window con- 
taining the footplate of the stapes, the pro- 
montory and the round window. Anterior to 
the horizontal portion of the facial canal is 
the process cochleariformis, a pulley-like struc- 
ture about which the tendon of the tensor tym- 
pani muscle curves before inserting on the 
neck of the malleus. 
The oval window, closed by the annular liga- 
ment and the footplate of the stapes, com- 
municates with the perilymphatic space of the 
vestibule. Below it the round window lies in a 
deep depression. It is closed by a membrane 
which separates the middle ear cavity from the 
scala tympani of the first turn of the cochlea. 
The promontory is a plate of bone which 
bulges into middle ear cavity. The first turn of 
the cochlea lies behind, or medial to the promon- 
tory. The facial nerve lies in a canal above the 
stapes and below the bulge of the horizontal 
semicircular canal. 
The posterior wall.—The posterior wall of 
the middle ear cavity is a continuation of the 
posterior wall of the external canal. It contains 
the continuation of the facial canal near its 
floor. The canal continues downward to emerge 
at the stylomastoid foramen on the inferior 
surface of the mastoid bone. This part of the 
canal contains the descending portion of the 
facial nerve. 
The facial nerve.—The facial nerve follows 
a tortuous path, receiving and sending off many 
branches in its course from the brain stem to 
its final distribution to the muscle of expres- 
sion of the face. Grossly, the nerve blends with 
the pars intermedia (or glossopalatine nerve) 
while it is still in the internal auditory meatus. 
It enters the facial canal, coursing forward and 
laterally to the facial knee (first portion). The 
geniculate ganglion is located at this point. 
From here the nerve bends backward, above the 
oval window as far as the posterior wall of the 
middle ear cavity (second portion). From here 
the nerve bends sharply downward to emerge 
from the stylomastoid foramen. Branches of 
the facial nerve given off within the facial 
canal are: 
1. The great superficial petrosal nerve. 
2. A twig to the stapedius muscle. 
3. The chorda tympani. 
4. Anastomotic branch with the tympanic 
plexus. 
The anterior wall.—The anterior or carotid 
wall of the middle ear contains the tympanic 
opening of the Eustachian tube, the bony canal 
of the internal carotid artery and the semicanal 
of the tensor tympani muscle. The Eustachian 
tube connects the tympanic cavity with the 
nasopharynx. It is about 37 mm. (1)/% inches) 
long and its direction from the tympanum i£ 
forward, downward, and inward. In the adult 
the pharyngeal opening is 15 mm. lower than 
the tympanic end. The tube is about one third 
bony and two thirds cartilaginous, the narrow- 
est part of the canal being at the junction of 
the two. It opens into the middle ear in the 
upper half of the anterior wall of the tym- 
panum. The osseous portion of the canal is 
always open but the trumpet-shaped pharyn- 
geal end is normally closed. It is open only 
during the act of yawning, or swallowing when 
the lower lip of the opening is pulled downward 
by the action of the levator and tensor pala- 
tini muscles. The tube is lined with ciliated 
epithelium continuous with the mucous mem- 
brane of the nasopharynx and the middle ear. 
90 Chapter 5. — OTOLARYNGOLOGY IN AVIATION MEDICINE 
THE TYMPANIC CAVITY 
The tympanic cavity contains the ossicular 
chain of the conduction system together with 
its muscles. The mucosa is more elevated at 
the mouth of the Eustachian tube and is cili- 
ated in character. The muscles include the 
tensor tympani and the stapedius. These are 
attached to the neck of the malleus and the 
stapes respectively. They are antagonists which 
act as a damper to prevent excessive movement 
of the ossicular chain during excessive stimu- 
lation. The body of the tensor tympani muscle 
lies in a semicanal above the Eustachian tube. 
Its fibers arise from the bony walls of this 
canal. It is innervated by the third division of 
the trigeminal nerve through the otic ganglion. 
The mastoid.—In the discussion of the pos- 
terior wall of the middle ear we failed to men- 
tion a very important opening, the mastoid 
antrum. This is the aperture through which 
the pneumatic cells of the mastoid bone com- 
municate with the middle ear and with the 
Eustachian tube and nasopharynx. The mas- 
toid process is formed by the union of processes 
of the squamous and petrous portions of the 
temporal bone. Pneumatization of the mastoid 
varies in different individuals but all the cells 
communicate with the antrum and all are lined 
with mucous membrane similar to that of the 
middle ear cavity. 
THE INTERNAL EAR 
The osseous internal ear.—The osseous in- 
ternal ear or bony labyrinth consists of the 
bony semicircular canals, vestibule and cochlea. 
It lies within the petrous portion of the tern- 
Figure 5-3. 
91 AVIATION MEDICINE PRACTICE 
poral bone. Laterally is the cavity of the mid- 
dle ear, medially the internal auditory meatus. 
Through the latter it connects with the pos- 
terior cranial fossa. It consists of very dense 
bone 2 to 3 mm. thick, the bony labyrinthine 
capsule of the petrous bone. The bony inner 
ear has five openings externally: (1) oval win- 
dow (closed by the stapes), (2) round window 
(closed by a membrane), (3) cochlear aque- 
duct, (4) vestibular aqueduct and (5) internal 
auditory meatus. 
The capsule surrounds a system of cavities 
in which three parts may be distinguished: a 
middle part, the vestibule—an interior, the 
cochlea—and a posterior, the three semicircular 
canals. Within the cavity of the bony labyrinth 
is a membranous counterpart—the membranous 
labyrinth. This is surrounded by supporting 
fluid and anchored to the walls of the bony 
labyrinth by numerous small trabeculae. The 
supporting fluid is called perilymph. The mem- 
branous labyrinth itself is filled witth endo- 
lymph. The inner ear is separated from the 
middle ear by the oval and round windows. The 
oval window is closed by the footplate of the 
stapes and the round window by a membrane. 
Physiologically the labyrinth contains two en- 
tities, the acoustic apparatus, consisting of the 
cochlea and perhaps the saccule and the ves- 
tibular apparatus which consists of the three 
semicircular canals and the utricle. 
The cochlea.—The bony cochlea is a short 
cone lying medial and slightly anterior to the 
middle ear cavity. The apex of the cone points 
anteriorly and laterally. It consists of two and 
a half turns about a central bony core, the 
modiolus. It is about 9 mm. in diameter and 
5 mm. high. The membranous cochlea is divided 
into three sections by the basilar membrane 
and Reissner’s membrane. The three divisions 
are the scala vestibuli which communicates 
with the oval window, the scala media which 
contains the organ of Corti, and the scala tym- 
pani which is separated from the middle ear by 
the round window membrane. 
The scala vestibuli and the scala tympani which 
contain perilymph are connected by a small 
opening at the apex of the cone, the helico- 
trema. The scala media contains endolymph 
and is not in connection with the perilymph 
of the scala vestibuli or scala tympani. The 
organ of Corti, bathed in endolymph, is the 
sensory end organ for the reception and con- 
version of sound impulses and is connected 
with the cerebral centers by the auditory 
(VUIth) nerve. 
Vestibule.—The vestibule is a small cavity 
separated from the middle ear by the oval win- 
dow. The vestibule contains two irregular sac- 
like organs, the utricle and saccule. The utricle 
connects with the membranous semicircular 
canals and forms part of the vestibular appara- 
tus. It also communicates through a narrow 
channel with the saccule which in turn joins 
indirectly with the scala media or ductus coch- 
learis. In the walls of both the utricle and the 
saccule rest delicate neuroepithelial organs 
called the .maculae. The utricle is thought to 
function as an equilibratory organ. The func- 
tion of the saccule is not known, although re- 
cent investigation indicates that it may have 
something to do with hearing. 
Semicircular canals.—The bony walls of the 
semicircular canals are curved tubes, three in 
number, nearly semicircular, each of which is 
connected in two places with the wall of the 
vestibule. They are not all of equal length but 
are almost uniform in diameter (1.5 mm.) They 
lie in three planes almost perpendicular to each 
other, any two forming a right angle. The hori- 
zontal canal is the shortest of the three and is 
directed laterally and backward. Laterally and 
forward it adjoins the recess epitympanicus, 
and there produces the prominence of the hori- 
zontal canal in the floor of the antrum above 
the horizontal portion of the facial nerve. 
The superior semicircular canal stands at 
right angles to the axis of the petrous portion 
of the temporal bone, making an angle of 45 
degrees with the sagittal axis of the skull. It 
is close to the surface of the bone, giving rise to 
the prominence called the eminence arcuata. 
The posterior semicircular canal is the longest 
of the three. It lies almost parallel to the pos- 
terior surface of the petrous bone. 
The membranous semicircular canals corre- 
spond in shape to the bony canals but with 
much smaller diameter. They join the utricle 
through the five openings in the walls of the 
vestibule. There are but five openings as the 
posterior and superior canals join and enter 
the utricle through a common opening. At one 
92 Chapter 5. — OTOLARYNGOLOGY IN AVIATION MEDICINE 
Figure 5-4. 
of the extremities of each semicircular canal 
is an enlargement called the ampulla. Each 
ampulla contains specialized nerve and hair 
cells, comprising the crista ampullaris, the es- 
sential sensory receptor of that canal. 
The structural arrangement of the semi- 
circular canals is such that stimulation re- 
sulting from movement of the head may be per- 
ceived in any combination of planes—hori- 
zontal, frontal or sagittal. If we consider the 
anterior vertical (superior) semicircular canal 
as forming half of a circle, then the other half 
of the circle is formed by the posterior vertical 
canal of the other side. The horizontal canals 
of the two sides form two segments of a circle 
in the same plane. The ampullated ends o£ all 
canals lie anterior and lateral to the smaller 
end. The ampullae of parallel canals are func- 
tionally opposed to each other. 
The utricle and saccule.—The semicircular 
canals comprise what is called the kinetic por- 
tion of the labyrinth. The utricle and saccule 
form the static portion. They lie in the cavity 
of the vestibule between the cochlea and the 
semicircular canals. They are small membra- 
nous sacs, the utricle being the larger of the 
two. The utricle receives the five openings of 
the membranous semicircular canals. It also 
has on one side an oval, thickened place of a 
whitish color, the macula acustica utriculi, in 
which terminate the fibers of the utricular 
nerve. 
The saccule is a flattened spherical vessel 
(2 mm. in diameter) situated in front and be- 
low the utricle. It communicates directly with 
the scala media of the cochlea. On the medial 
surface there is a thickened area in which 
terminate the fibers of the saccular nerve. The 
saccule is connected with the utricle only in- 
directly through the endolymphatic duct. This 
duct ends in a blind cecal dilatation under the 
dura of the posterior surface of the petrous 
bone. The peripheral end organ of the vesti- 
bular apparatus consists of the crustae and 
93 AVIATION MEDICINE PRACTICE 
Figure 5-5. 
maculae of the three semicircular canals, the 
utricle and the saccule. 
The eighth or auditory nerve has a cochlear 
portion which transmits the auditory stimuli 
from the cochlea and a vestibular portion which 
transmits stimuli from the cristae ampullaris 
of the semicircular canals and the maculae of 
the utricle and saccule. The two portions of the 
nerve join and leave the temporal bone through 
the internal auditory meatus along with the 
facial (seventh) nerve. The cochlear and vesti- 
bular nuclei lie in the brain stem near the 
fourth ventricle. 
PHYSIOLOGY OF THE 
EAR, NOSE AND THROAT 
PHYSIOLOGY OF THE EAR 
The external and middle ear.—The lobe of 
the external ear, the concha and the external 
canal serve to concentrate the sound waves and 
deliver them to the tympanic membrane. The 
handle of the malleus is incorporated in the 
membrane itself. By means of the three ossicles 
the sound waves are transmitted from the 
tympanic membrane to the footplate of the 
stapes in the oval window. In this manner vi- 
brations are transmitted to the fluid of the 
cochlear chambers. Owing to the leverage ar- 
rangement of the ossicular chain the sound 
waves are transmitted to the cochlea decreased 
in amplitude but increased in intensity. The 
tensor tympani and the stapedius muscles are 
attached to the neck of the malleus and to the 
stapes respectively. These muscles are antago- 
nists which contract in response to strong 
stimulation. By decreasing the amplitude of 
movement of the ossicular chain they produce 
a damping effect on the movements of the 
mechanism of the ear. 
The middle ear is connected with the naso- 
pharynx by the Eustachian tube. In this way at- 
mospheric pressure is maintained in the middle 
94 Chapter 5. — OTOLARYNGOLOGY IN AVIATION MEDICINE 
Figure 5-6. 
ear and the pressure on either side of the tym- 
panic membrane is equal. Disease of the naso- 
pharynx which interferes with the patency of 
the Eustachian tube also interferes with the free 
movement of the tympanic membrane and the 
ossicular chain, causing deafness. 
It has been shown experimentally that an in- 
tact drum is not essential for normal hearing. 
Any interference with the ossicular chain, how- 
ever, is very likely to result in some hearing 
loss. 
The internal ear.—The membranous internal 
ear consisting of the labyrinthine and cochlear 
portions occupies a small chamber in the tem- 
poral bone. The parts are bathed in common 
fluids, the perilymph without, the endolymph 
within, so that infection is readily carried from 
one part to the other. The blood supply of the 
internal ear is supplied mostly by the internal 
auditory artery, a branch of the basilar artery. 
It is an end artery with three branches. One 
branch supplies the cochlea, one the labyrinth 
and the third a portion of each. Occlusion of 
any of these branches results in immediate loss 
of function of that part of the internal ear 
which it supplies. 
The nerves from the cochlea and the laby- 
rinth have a common and united course into the 
medulla. In a clinical examination it is im- 
portant to test both branches of the nerve. 
There are times when an indefinite hearing 
test may be established beyond all doubt by the 
result of the labyrinthine examination. 
The cochlea.—From the footplate of the 
stapes the sound waves enter the cochlea. The 
membranous cochlea consists of a tube coiled 
on itself two and a half times around a rela- 
tively hollow core, the modiolus. This tube is 
enclosed in a dense bony covering which is 
coiled to resemble a shell. Hence, the name 
95 AVIATION MEDICINE PRACTICE 
cochlea. The perilymph is contained in two 
chambers or tubes, one above the cochlear duct 
called the scala vestibuli and one below the 
cochlear duct called the scala tympani. These 
tubes or chambers of perilymph join at the 
top of the cochlea, the helicotrema. The scala 
vestibuli begins at the footplate of the stapes 
in the oval window. It joins the scala tympani 
at the helicotrema. The scala tympani extends 
down from the helicotrema to end at the round 
window which is closed by a membrane. From 
the floor of the scala tympani a canal leads to 
the subarachnoid space in the cranial cavity 
near the jugular foramen. This canal, called 
the aqueductus cochlea, is filled with areolar 
tissue. Through it, there is a connection be- 
tween the perilymph and the cerebro-spinal 
fluid. 
A cross section from above down through the 
cochlea shows the modiolus in the center and 
the cochlear duct with its scalae at slightly dif- 
ferent levels on either side. On examination 
of a cross section one sees coming off from the 
modiolus a bony shelf, the spiral lamina, to 
which the cochlear duct is attached internally. 
The outer side of the duct is anchored to the 
external wall by a ligamentous structure called 
the spiral ligament which follows it from the 
basal coil to the top. The cochlear duct is 
closed above by a thin loose membrane which 
is attached internally to the upper surface of 
the bony lamina and externally high up on the 
lateral bony wall. It is called Reissner’s mem- 
brane, The floor of the duct, the basement 
membrane, extends from the spiral lamina to 
the spiral ligament. It is a firm tense band of 
laterally placed fibers and it is these fibers 
which are generally considered to be the vibrat- 
ing or resonating elements of the cochlea. Rest- 
ing on the basement membrane at its inner 
attachment is the actual nervous end-organ of 
hearing, the organ of Corti. 
The organ of Corti consists simply of several 
rows of nervous hair cells which are held to- 
gether by longer and firmer supporting cells 
which rest directly on the basement membrane. 
The tops of the hair cells project just above 
the level of the tops of the supporting cells of 
Deiter. Lateral to these are other types of 
supporting cells, including the fat-containing 
cells of Hensen. Over the point of attachment 
of the basement membrane to the bony lamina 
two of the supporting cells are modified to form 
rod-shaped structures called the rods of Corti. 
These rods are wide apart at their attachment 
to the basement membrane below; above they 
are in contact. By this arrangement a tunnel 
is formed which extends from the base to the 
apex of the cochlear duct. The hair cells are 
arranged in three rows external to Corti’s rods 
and one row internal to Corti’s rods. The 
nerves pass from the base of these cells into 
canals in the bony lamina, through which they 
enter the modiolus. There they join the spiral 
ganglion, then pass into the internal auditory 
meatus to form part of the eighth nerve along 
with the vestibular branches. 
Just above the level of the hair cells of Corti’s 
organ is the tectorial membrane. It is attached 
at its inner end to the upper surface of the 
spiral lamina. Its histology is still in doubt. 
Gray believes that it is a gelatinous membrane 
into which the hair cells of the organ of Corti 
project, as the gelatinous cupola overlies the 
cristae in the ampullae of the semicircular 
canals. 
At the base of the cochlea the basement mem- 
brane is very narrow. It becomes progressively 
wider toward the apex until at the top coil 
the individual fibers are about three times as 
long as they are at the base. This fact is of 
importance as will be demonstrated when we 
discuss the theories of hearing, especially the 
resonance theory of Helmholtz. 
The cochlear nerve.—The nerves from the 
cochlea and the labyrinth run together until 
they reach the medulla but from these they 
diverge widely. The cochlear nerve has reflex 
connections in the brain stem but it is mainly 
connected with the cortex of the temporal lobe 
of the same and opposite side. Recent experi- 
mental work indicates that the cochlea on one 
side sends an equal number of fibers to both 
temporal lobes—a symmetrical bilateral corti- 
cal representation. 
After entering the medulla the cochlear fibers 
end about the cochlear nuclei which are in close 
relationship to the inferior cerebellar peduncles. 
From these nuclei some of the fibers run dor- 
sally across the floor of the fourth ventricle 
to the lateral fillet of the opposite side. Others 
run ventrally as the trapezoid body to the lat- 
96 Chapter 5. — OTOLARYNGOLOGY IN AVIATION MEDICINE 
eral fillet and ascend to the inferior corpora 
quadrigemina and medial geniculate body of 
the opposite side. Some fibers go to the lateral 
fillet of the same side; some to the nuclei of the 
nerves to the extraocular muscles. These latter 
are responsible for the associated movement of 
the eyes in response to sound. From the in- 
ferior quadrigeminal body and the medial 
geniculate body fibers pass to the auditory 
center in the cortex of the temporal lobe. 
Numerous decussations connect the various 
centers on the two sides. Because of the 
symmetrical bilateral representation of each 
cochlea in the brain it is rare to find deafness 
associated with any lesion in the brain situated 
above the level of the cochlear nuclei. Dr. 
Dandy has been able to remove the entire 
temporal lobe on one side without being able 
to detect an appreciable hearing loss. From 
this and a mass of other experimental data it 
follows that a lesion causing hearing loss is 
situated in or peripheral to the cochlear nuclei. 
PHYSIOLOGY OF SOUND PERCEPTION 
The cochlear apparatus.—This may be de- 
fined as a group of structures for the collection, 
transmission and registration of auditory 
stimuli. 
The physical basis of hearing.—Two agencies 
are necessary for the production of sound. The 
first is a vibrating body such as a resonator, 
tuning fork, or vibrating string. The second 
requirement is an elastic medium by which the 
vibrations thus produced can be propagated 
some distance away to reach the ear of the 
observer. The medium most commonly used is 
air, but liquids, gases, and even solids can 
transmit sound. 
The vibrations imparted to the air by a 
sound-producing mechanism are commonly spo- 
ken of as sound waves. The disturbance created 
consists of an alternating series of condensa- 
tions and rarefactions propagated in a pendular 
manner in all directions. Sound, accordingly, 
is the sensation produced on the receiving ap- 
paratus by alternating rarefaction and conden- 
sation of air giving rise to sound waves. Two 
types of sound exist, viz., notes and noises, 
Sound waves which form the units of hearing 
have certain attributes: loudness or intensity. 
pitch, and quality or timber. Frequency is the 
number of back-and-forth vibrations (double 
vibrations) of its particles in a given unit of 
time. The rate of vibration determines the 
pitch of a sound, high notes corresponding to 
waves which oscillate very rapidly, low tones 
to those of much lower speed. The range of 
hearing for the human ear lies between 12-and 
28-thousand double vibrations per second. Am- 
plitude is the distance traversed by a particle in 
its to-and-fro swing: graphically this is repre- 
sented by the distance between the crest and 
trough of a wave. The third attribute of a 
sound is timber, a distinguishing quality apart 
from pitch or loudness characterizing sounds 
produced by different instruments, such as the 
piano, violin, or human voice. 
Sound is practically always a combination of 
several frequencies and amplitudes. It is the 
function of the auditory mechanism not only 
to register these sound patterns but to interpret 
them in the light of past auditory experience, as 
musical notes, noises, or human speech com- 
ponents. A tone is sound produced by a number 
of equal and regular vibrations, while noises 
are vibrations which are irregular in length 
and time. Sound is a form of energy, the term 
being used by the physicist to designate the 
pressure waves that travel outward through 
air, fluid, or solid from any vibrating source. 
A sound may also be a mixture of many fre- 
quencies, as in a musical chord, or it may be an 
irregular mixture of waves of different wave 
lengths including a single spikes or transients. 
Such an irregular mixture is called a noise. 
Speech is a composite of more or less pure 
tones and of noise, changing in composition 
and intensity from moment to moment. The 
intensity of the faintest sound that can be 
heard is known as its threshold. Naturally the 
threshold is not a constant unit but varies with 
the variations in individual auditory acuity. 
Frequency of sound or pitch is measured in 
double vibrations per second. Intensity is mea- 
sured in decibels. This unit is the minimal 
identifiable auditory increase at threshold level. 
Perception of sound by the human ear covers 
the range from 16-to-22 thousand double vibra- 
tions per second. The useful range of the hu- 
man voice lies between 256 and 2,048 d.v./sec. 
The behavior of certain animals indicates that 
97 AVIATION MEDICINE PRACTICE 
their ears are sensitive to vibrations as high 
as 40-or-50 thousand cycles. 
THEORIES OF HEARING 
There continues to be much discussion con- 
cerning the mechanism whereby mechanical vi- 
brations of the air are analyzed and interpreted 
as sound. It centers around two main hypo- 
theses; whether sound falling upon the ear is 
analyzed peripherally in the internal ear or 
centrally in the brain. 
Central analysis.—The theory of central an- 
alysis is called the frequency or telephone the- 
ory, It presupposes that the sound is received 
in the cochlea from which nerve impulses of 
the same frequency as the stimulating sound 
are transferred to the nerve and are carried 
to the auditory centers in the brain where an- 
alysis takes place. 
Peripheral analysis.—The theory of peri- 
pheral analysis is commonly called the reson- 
ance theory and is associated with the name of 
Helmholtz. It presumes that the cochlea con- 
sists of a series of resonating elements by 
which complex sound vibrations are broken up 
and analyzed into their simple constituent har- 
monic components so that the stimuli trans- 
mitted to the nerve fibers are simple nerve im- 
pulses from the different sections of the base- 
ment membrane. This latter theory is the more 
generally accepted. 
The proponents of the resonance theory state 
that the transverse sectors of the basilar mem- 
brane when vibrating conform to the law of 
stretched strings. In order to respond to differ- 
ent sound frequencies the sectors must vary in 
tension, in length, and in mass or load. It is 
known that the fibers of the basilar membrane 
are three or four times as long at the apex of 
the coil as at the base. It is also an anatomical 
fact that the spiral ligament is much larger at 
the base of the cochlea than at the apex. This 
is interpreted as indicating that the short fibers 
near the base are under higher tension than the 
long fibers at the apex. Hallpike has shown 
that in the guinea pig the supporting cells of 
Hensen contain more fat at the apex of the 
cochlea than they do at the base. This causes 
a heavier fluid load or damping effect on the 
apical fibers. 
In support of the resonance theory then we 
find that the short fibers of the basilar mem- 
brane are in the basilar coil of the cochlea 
where they are stimulated by high pitched 
sounds. It is computed that this variation in 
length alone will account for about one and one- 
half octaves of hearing. The thick heavy spiral 
ligament found in the basilar coil puts greater 
tension on the short fibers of the basilar coil 
than it does on the long fibers near the apex 
where the ligament is smaller. This variation 
in tension is computed to account for a range 
of hearing of seven octaves. The damping effect 
on the fibers near the apex is greater than at 
the base due to the increased amount of fat in 
the cells of Hensen in the apical coils. These 
three factors: variation in length of fiber, ten- 
sion, and mass are calculated to account for 
a range of hearing of about 11 octaves, ap- 
proximately that of the human ear. 
Various other theories have been advanced 
but the majority of experimental work supports 
the idea of pitch localization on the basilar 
membrane. The mechanism as outlined above is 
undoubtedly an over-simplification of a very 
complex procedure, but present evidence seems 
to point to some form of pitch localization on 
the basilar membrane. While anatomical study 
and experimental research indicate the prob- 
ability that sound is analyzed peripherally, it 
is still not a proven fact. Even if it is assumed 
with Helmholtz and his followers that a certain 
amount of sound analysis takes place in the 
cochlea, it is apparent that in man, at least, 
hearing is a cerebral function. 
The external ear, the tympanic membrane, 
and the ossicles make up the conduction appara- 
tus of the ear. The cochlea, the auditory nerve, 
its nuclei, and the complex cerebral connec- 
tions of the auditory pathway make up the per- 
ceptive apparatus. Since this highly complex 
mechanism is concerned with the conduction 
and perception of sound, it follows that any 
condition causing interference with the con- 
ducting mechanism would result in a condvc- 
tion deafness. Similarly a lesion in the percep- 
tive mechanism would result in a perception 
deafness. Lesions in both the conduction and 
the perception systems result in a mixed type 
of deafness. In conductive type of deafness 
the hearing loss is most marked in the lower 
98 Chapter 5. — OTOLARYNGOLOGY IN AVIATION MEDICINE 
tones. In the perceptive type of deafness, on 
the other hand, the high tones are lost first. 
EXAMINATION OF THE 
EAR AND FUNCTIONAL TESTS 
The external ear and typmanic membrane.— 
Inspection and palpation of the external ear, 
the canal, and surrounding structures is im- 
portant. Palpation of the areas about the ear 
may reveal swelling of soft tissues over the 
mastoid process or enlarged and tender cervi- 
cal lymphnodes. Pressure on the tragus or pull- 
ing the pinna upward may cause pain, indicat- 
ing the presence of an external otitis. To visu- 
alize the external canal and the tympanic mem- 
brane it is necessary to have a good light the 
rays of which can be projected into the canal 
parallel to the line of vision. 
Occasionally it is possible to visualize the 
canal and the tympanic membrane by pulling 
the pinna upward and the tragus slightly for- 
ward. More commonly it is necessary to intro- 
duce an ear speculum of appropriate size, de- 
pending on the size and shape of the canal. 
Usually it is not possible to see the entire tym- 
panic membrane without tilting the speculum 
slightly from side to side. 
Hearing tests.—There are two types of hear- 
ing tests; those carried out with the voice and 
those with instruments for producing certain 
standard tones within the human hearing 
range. The purpose of the tests is to determine 
the degree and type of any deafness. They 
are also useful in helping to diagnose certain 
diseases of the ear and to separate diseases of 
the sound conduction apparatus from those of 
the sound perception apparatus. The tests em- 
ployed are: 
1. Conversational and whispered voice. 
2. Tuning forks. 
3. Whistles or the monochord. 
4. The audiometer. 
Speech tests.—Tests with the voice include 
use of the ordinary speaking voice and the 
unaccentuated whisper. The patient stands at 
the end of a room or hall at least 20 feet in 
length, so constructed that extraneous sounds 
are excluded. The patient, with eyes closed, 
stands with the ear being tested toward the ex- 
aminer, the other ear being occluded by the 
finger or a Barany noise maker. The noise ap- 
paratus is used to exclude sound of the test 
words or sentences from entering the ear which 
is not being tested. Test words or sentences are 
spoken by the examiner in an even, conversa- 
tional tone, beginning at the greatest distance 
and approaching slowly until the subject is able 
to repeat them accurately. The whispered voice 
is also used, a whisper being lower in volume 
but higher in frequency than the spoken voice. 
In using the whisper test the examiner uses 
only the residual air, that in the lungs after a 
normal exhalation. 
The tympanic membranes should always be 
examined during the clinical examination to 
test hearing. Occlusion of the external audi- 
tory canal by cerumen may result in conductive 
type of deafness. It is also to be remembered 
that otosclerosis and inner ear disease are the 
only types of deafness in which a normal tym- 
panic membrane is usually present. 
Tuning forks.—Instrumental tests are de- 
signed to furnish the means for diagnosing the 
type of hearing impairment as well as the ex- 
tent of the damage. By the use of tuning forks 
we can ascertain whether a hearing loss is due 
to a lesion of the conduction apparatus or of 
the perceptive apparatus. To do this we test 
the bone conduction, the direction in which a 
fork placed on the vertex is lateralized, the rela- 
tive length of time a fork is heard by air as 
compared with bone (over the mastoid process 
of the same ear), and the range of hearing 
as determined by the lowest and highest tone 
that can be heard. 
When testing bone conduction a control is 
used, the examiner’s own conduction or an ob- 
jective control, in which the criterion is the 
average duration of time that a testing fork 
is heard by bone in a series of normal beings 
previously tested with the same fork. 
The tuning forks in general use include: 
C = 64 d.v.s. used for testing low tones, 
c = 128 d.v.s. employed for the Weber test, 
c, = 256 d.v.s, used for the Rinne test, a, = 
435 d.v.s. is also used. 
c, = 2048 d.v.s. for testing high tone limit. 
These forks suffice for all practical purposes, 
the normal tonal range being amply repre- 
sented. Some prefer the c, (256 d.v.s. fork, 
however, for the air and bone conduction deter- 
99 AVIATION MEDICINE PRACTICE 
Figure 5-7.—Weber test. 
100 Chapter 5. — OTOLARYNGOLOGY IN AVIATION MEDICINE 
Figure 5-8.—Rinne test. 
minations. Others prefer an a, fork (435 d.v.s) 
in the Rinne test and the unweighted A fork 
(108 d.v.s.) for the Weber and Schwabach 
tests. A national committee on hearing and 
tuning fork tests has recommended that only 
three standard tests be considered: namely, the 
Weber, the Schwabach, and the Rinne. The 
Weber and Schwabach are performed by plac- 
ing the fork on the median line of the vertex 
or forehead, and for this purpose a fairly heavy 
fork resting largely by its own weight is desir- 
able. 
The Weber test.—This test determines 
whether the sound is perceived in the vertex 
(the patient says “heard in the head”) or 
whether the tone of the fork is lateralized, that 
is, seems louder or entirely in one ear or the 
other. The result is recorded as “not lateral- 
ized” or “lateralized to the right or left” as 
the case may be. 
With the tuning fork resting on the vertex 
of the head, part of the sound goes directly to 
the labyrinth through the skull. This is known 
as direct bone conduction. Another part of the 
sound goes through the skull to the tympanic 
cavity. This is known as indirect bone conduc- 
tion. A part of this is reflected to the inner 
ear and part to the outside where it is lost. 
This happens normally on both sides but if one 
ear is closed the sound is heard much better 
on this side because the sound usually reflected 
to the outside is now reflected back toward the 
101 AVIATION MEDICINE PRACTICE 
inner ear. This is the case in lesions of the mid- 
dle ear or external canal. In lesions of the in- 
ner ear the perception of direct bone conduction 
is interfered with so that sounds are heard best 
on the unaffected side. 
The Rinne test.—This test is a comparison 
of bone (BC) and air (AC) conduction. Air 
conduction is normally longer than bone con- 
duction. A medium pitched fork is placed 
on the mastoid until the patient states that he 
no longer hears it. It is then placed in front 
of the tragus until he can no longer hear it 
by air conduction either. When air conduction 
time is greater than bone conduction the Rinne 
is said to be positive. This is the normal condi- 
tion. In middle ear disease the air conduction 
is impeded so that hearing by bone is greater 
than by air (negative Rinne). In inner ear 
disease bone conduction is impaired so that air 
conduction is increased over that of bone con- 
duction. While this is also a positive Rinne the 
ratio is far greater than that of a normally 
positive Rinne. 
Schwabach test.—In this test the fork is 
placed on the mastoid process back of the ear. 
The object is to compare the bone conduction 
of the subject with the normal. The fork is 
lifted from the head every few seconds and 
then replaced after a rest of a few seconds. This 
prevents fatigue of the nerve and gives a more 
reliable result. If the observer does not know 
the normal bone conduction time of his particu- 
lar fork he may either use his own conduction 
time or that of any normal young adult. By 
this method it is possible to tell whether the 
subject’s bone conduction is “normal,” “short- 
ened” or “very much shortened.” In cases of 
middle ear disease bone conduction is increased, 
consequently the Schwabach is lengthened. 
Having mentioned the lengthened Schwabach 
test associated with lesions of the conduction 
mechanism this will be a good time to speak of 
the mechanism of masking. As our environ- 
ment is practically never completely quiet, our 
ears are constantly being bombarded by a mul- 
titude of extraneous sounds. In listening to 
conversation or music our ears are constantly 
having to strain out the sounds we wish to hear 
from the incidental noise about us. The more 
noisy the environment the louder will a person 
addressing us have to speak in order for us to 
hear distinctly what he is saying. In a case 
of middle ear disease external sounds are im- 
peded by the lesion and air conduction will be 
reduced. Now, if we place a vibrating fork 
on the bony prominence behind such an ear 
bone conduction will be increased because the 
sound of the fork does not have to compete 
with extraneous noises coming in over the con- 
duction apparatus. This masking effect is 
simply illustrated by placing a tuning fork on 
your own ear and then closing the ear with a 
finger. The sound of the fork will then appear 
louder and more prolonged. 
Masking.—Masking is useful in attempting 
to establish a clear picture in monaural deaf- 
ness. We may get erroneous answers while 
testing the bone conduction of a deaf ear be- 
cause the sound is being heard in the other or 
normal ear. So it is frequently necessary to try 
to mask the good ear by means of one of the 
various types of noise makers now available. 
Low and high limit tests.—The lowest note 
that the ear can hear may be tested by use of a 
fork with a frequency of 16 or 32 d.v.s. For 
high notes it is necessary to use a monochord or 
a Galton whistle. These devices produce tones 
of high frequency, the instrument being adjust- 
able to produce a desired tone. 
The audiometer.—The audiometer is an elec- 
trically controlled apparatus by which accurate 
measurements of hearing are obtained and 
charted in sensation units. The apparatus now 
in use is a vacuum tube oscillator which gene- 
rates approximately pure tones over a wide 
range of frequency and intensity. It is essen- 
tial that these instruments be standardized 
and calibrated properly. Audiometers are cali- 
brated in decibels in frequencies from 64 to 
8,192 double vibrations per second. 
CLINICAL AND PHYSICAL APPLICATION 
Taking 16 double vibrations per second as 
the lower tone limit and 28 thousand as the 
upper tone limit, the following variations may 
occur. In middle ear disease the low tone limit 
is raised in comparison with that of the normal 
person. The bone conduction is increased and 
therefore greater than air conduction (Rinne 
negative). In inner ear disease in the early 
stages all the tones can be heard except the 
102 Chapter 5. — OTOLARYNGOLOGY IN AVIATION MEDICINE 
higher ones. Bone conduction is reduced, air 
conduction being greater than that by bone. 
The Rinne is positive. In combined forms of 
deafness the tone limit is narrowed from above 
and below. 
In hysterical deafness all hearing is by air 
and absolutely none by bone. This gives an 
“infinitely positive Rinne.” An infinitely nega- 
tive Rinne is obtained in a case of unilateral 
deafness. There is no air conduction and the 
only bone conduction is that heard in the other 
ear which is really “borrowed” bone conduction. 
A doctor is sometimes asked to determine 
whether or not an infant can hear. Certain 
reflexes are useful in this respect. (1) Acousti- 
cal palpebral reflex. The palpebral fissure will 
narrow after a sudden loud sound. (2) Acousti- 
cal pupillary reflex. Sudden loud noise causes 
contraction of the pupils. (3) Acoustical muscu- 
lar reflex. Limbs will jerk at a sudden fright- 
ening noise. Any of these tests, if positive, 
prove the presence of hearing. Even if all three 
are negative it does not prove lack of hearing. 
Malingering.—People feigning deafness rare- 
ly claim bilateral hearing loss. Usually they 
insist that they have total hearing loss on one 
side. Several tests have been devised to help 
detect the malingerer. 
1. Weber Test. With fork on vertex and a 
finger in the good ear, he claims he hears poorly 
or not at all. A normal person hears better with 
ears occluded. 
2. A person with normal hearing will raise 
his voice when speaking or reading in a noisy 
atmosphere. Place a Barany noise maker in the 
supposedly good ear of the suspect and ask him 
to read. If his hearing is good in the other ear 
he will not raise his voice. 
3. Stenger Test. This is done with two forks 
of 435 d.v.s. If a fork is placed outside each 
ear the subject with normal hearing will hear 
only the closer fork. Place a fork close to the 
supposedly deaf ear, the other fork slightly 
farther away from the good ear. If he is really 
deaf he will hear only the sound in the good 
ear. If he is malingering he will hear only the 
fork close to the “bad ear” and will claim that 
he hears nothing. Put forks to both ears, allow- 
ing him to see the one before the good ear. 
Dampen this fork without his knowledge. He 
will still claim to hear the fork in his good 
ear. 
4. By means of a special stethoscope ar- 
rangement have two observers talk into the pa- 
tient’s two ears. Hearing two voices at the 
same time the malingerer will be unable to 
prevent becoming confused and will trap him- 
self. 
DISEASES OF THE EXTERNAL EAR 
Frostbite.—The ears of some persons are 
sensitive to extreme changes of temperature, 
the effects of which may vary from slight hy- 
peremia to profound ischemia, terminating in 
local gangrene. At first hyperemic, the tissue 
soon becomes blanched, waxy, and vesiculated. 
The area undergoing such changes is demar- 
cated, and if infection sets in, becomes ulcer- 
ated and even gangrenous. The best treatment 
is prophylactic, especially if the ears have al- 
ready been frostbitten once. The circulation 
should be restored gradually by keeping the 
patient in a cool room. Cold compresses ap- 
plied to the ear will prevent too sudden a return 
of circulation. Necrotic tissue must be re- 
moved, gangrenous areas allowed to separate 
spontaneously. After removal of nonvital tis- 
sue the denuded area should be touched with 
silver nitrate, 25 to 50 percent. 
Hematomai.—The diagnosis is easy. Soon 
after trauma there is rapid effusion of blood 
between the cartilage and the perichondrium. 
A round, soft, bluish-red swelling forms quickly 
on the anterior surface of the auricle, obliterat- 
ing the contour of the helix and antihelix. If 
seen early the contents of the hematoma may 
be aspirated. If late, it is often necessary to 
incise and express the clott. A snug dressing- 
after evacuation of the clot will help prevent 
recurrence. The dressing should be maintained 
for 24 hours. 
Acute perichondritis and abscess.—Acute 
perichondritis may be either a serious or sup- 
purative exudation beneath the perichondrium 
of the ear. In addition to trauma, poor nutri- 
tion and certain infectious diseases have caused 
the serous type. The suppurative type, fre- 
quently with abscess formation, usually has a 
definite history of infection or trauma. Conser- 
vative treatment consists chiefly of supportive 
103 AVIATION MEDICINE PRACTICE 
measures. Dry or moist heat helps hasten ab- 
sorption. It is sometimes helpful to aspirate 
the fluid from the collections under the peri- 
chondrium. A snug dressing over a mold of 
dental compound will help maintain the shape 
of the ear. 
Sebaseous cysts.—Because of the necessity 
for wearing close fitting helmets and radio ear- 
phones by airmen, sebaceous cysts about the 
auricle should be mentioned. As elsewhere on 
the body the treatment of choice is complete 
extirpation of the sac. 
DISEASES OF THE 
EXTERNAL AUDITORY CANAL 
Foreign bodies.—These may be either ani- 
mate, organic or inorganic, (a) Animate for- 
eign bodies include a great variety of insects. 
Methods of removal vary from holding a light 
near the ear to spraying chloroform vapor into 
the canal. A simple method is to fill the canal 
with oil, after which the canal is syringed with 
warm water, (b) In removing other foreign 
bodies it is important to know whether or not 
they are hygroscopic. Those which will not 
absorb water may be washed out. If instru- 
mentation is necessary the greatest care should 
be exercised to prevent injury to the thin and 
delicate skin of the bony portion of the canal. 
Even impacted cerumen can usually be re- 
moved by means of a forceful stream of water. 
The use of sterile water is indicated for many 
a doctor has washed cerumen from an external 
canal only to find a perforation in the tympanic 
membrane. 
Furuncle of the external auditory canal.— 
These usually occur in the cartilaginous portion 
of the canal. The bony portion of the canal does 
not have hair follicles, sebaceous or sweat 
glands, the routes by which infection most 
commonly enters the skin. Pain is the out- 
standing symptom. As the skin is closely at- 
tached to the underlying cartilage there is little 
subcutaneous tissue present. A slight amount 
of swelling causes tenseness of the area with 
production of pain out of all proportion to the 
size of the lesion. Because of this the patients 
usually seek medical aid early. If the lesion is 
not obvious it may be located by touching dif- 
ferent parts of the canal wall with a cotton- 
tipped applicator. 
In the diagnosis of furunculosis it must be 
remembered that any disease which attacks 
skin elsewhere may involve the external audi- 
tory canal. In the majority of cases the differ- 
ential diagnosis lies between otitis media and 
mastoiditis. With the advent of the antibiotics 
and the subsequent decrease in the number of 
cases of mastoiditis, even this is no longer 
literally true. Perhaps the cardinal point in 
furunculosis is the negligible reduction in hear- 
ing. In mastoiditis and otitis media there is 
marked hearing loss. In furunculosis tender- 
ness over the mastoid is elicited on superficial 
pressure on the tragus, or lifting the auricle, 
while in mastoiditis the pain is deepseated. 
Roentgenograms are useful in determining bone 
pathology or cloudiness of the mastoid. 
In treatment of furunculosis the first con- 
sideration is given to control of the pain. Warm 
moist compresses over the auricle, alternating 
with dry heat give the best results. After locali- 
zation, incision of the abscess will hasten reso- 
lution. Loose packing of the canal with alcohol 
saturated strips of gauze is helpful. Or cresatin 
or phenol-glycerin (5 percent) may be used. 
In severe cases chemotherapy should be em- 
ployed. 
Otomycosis.—Of all the conditions which 
may involve the external ear canal perhaps the 
most common is otomycosis. This is especially 
true in temperate and tropical areas. Of the 
various fungi aspergillus is most frequently the 
causative organism. As a moist, warm environ- 
ment favors the growth of the organism it is 
not surprising that it is so common in the 
external canal. Among swimmers it is of fre- 
quent occurrence, the maceration of the skin of 
the canal being a contributing factor. Treat- 
ment consists primarily of thorough cleaning 
and drying of the canal wall, vigorous wiping 
of the skin with alcohol and dusting the dry 
surface with some antiseptic powder such as 
sulfathiazole or boriciodine. 
Injuries of the tympanic membrane.—This 
may follow direct trauma such as careless in- 
strumentation or indirect violence such as oc- 
curs from a slap on the ear or entering the 
water incorrectly when diving. It is the pri- 
mary finding in aero-otitis where the causative 
104 Chapter 5. — OTOLARYNGOLOGY IN AVIATION MEDICINE 
factor is a difference in air pressure on the 
two sides of the tympanic membrane. The evi- 
dence of injury may vary from the slightest 
hyperemia to a ragged perforation of the tym- 
panic membrane. In cases of head injury with 
fracture into the middle ear the possible com- 
plications and consequences are extremely seri- 
ous. In most cases, however, the treatment con- 
sists of watchful waiting. It is not even ad- 
visable to attempt to clean the external canal, 
the possibility of introducing infection into the 
middle ear being greater than the danger of 
leaving it alone. Hemorrhages or exudates into 
the membrane are absorbed spontaneously. The 
great majority of lacerations will heal by scar 
tissue formation in a few weeks. 
Aero-Otitis Media.—This is an acute or chron- 
ic traumatic inflammation caused by a pres- 
sure difference between the air in the middle 
ear and the surrounding atmosphere. It is 
characterized by pain, tinnitus, and occasionally 
vertigo. It is perhaps the most common otitic 
disorder among flying personnel today. In 
modern aircraft, and particularly in military 
aircraft, the body must compensate for rapid 
changes in atmospheric pressure. At 18,000 
feet the atmospheric pressure is roughly half 
of that at sea level (760 mm. Hg). At 33,000 
feet it is roughly one-fourth, or only 196 mm. 
Hg. 
Present day planes are capable of ascending 
and descending several thousand feet per min- 
ute. It is essential that there be ready inter- 
change of air between the middle ear and the 
external air in order to maintain equal pressure 
on the inside and outside of the tympanic mem- 
brane. A pressure differential of only 5 pounds 
is sufficient to rupture an eardrum. 
Under normal conditions atmospheric pres- 
sure is maintained inside the middle ear cavity 
through the Eustachian tube. This is a narrow 
mucous-membrane lined tube leading from the 
anterior wall of the middle ear to the naso- 
pharynx. The paryngeal end of the tube is slit- 
like in shape and the lumen is closed except 
during the acts of yawning, swallowing, chew- 
ing, etc., At such times the action of the leva- 
tor and tensor palati and the salpingopharyn- 
geus muscles exert tension on the lower lip of 
the opening of the Eustachian tube. 
During ascent the air in the middle ear ex- 
pands as the external pressure decreases. The 
excess air passes out through the Eustachian 
tube without difficulty: the individual may hear 
a snapping noise in the ear or feel a sensation 
as of bubbles moving through the tube. 
When the atmospheric pressure is increased 
instead of decreased, a totally different effect is 
produced. The collapsed pharyngeal end of the 
Eustachian tube then acts as a flutter valve 
preventing entry of air. When the subject 
swallows, the lips of the tubal opening are 
pulled apart and air rushes into the middle 
ear, equalizing pressures within and without 
immediately. This is the usual mechanism by 
which pilots keep pressure on the two sides of 
the eardrum equalized during descent to lower 
altitudes. If, however, the pressure differential 
equals 80 mm. Hg. or more the Eustachian 
muscles can no longer open the tube. In such 
cases it is necessary to reduce the external 
pressure by climbing a few hundred feet. 
During ascent there may be symptoms of 
fullness in the ear associated with tinnitus and 
occasionally pain. These are rarely severe as 
a pressure within the middle ear of 30 mm, Hg. 
or so is sufficient to force the air out the 
Eustachian tube with immediate relief. When 
letting down from higher to lower altitudes it 
is necessary for the individual frequently to 
open the tube and equalize the pressure by swal- 
lowing or yawning. 
When a man is unable to equalize the pres- 
sure in his ears by conscious effort during des- 
cent there is a rapid onset of deafness, tinnitus, 
and pain in the ear. Vertigo may be present. 
At a negative pressure of 60 to 80 mm. Hg. 
the pain is severe. At a differential pressure 
of 100 to 500 mm. Hg. the membrane ruptures. 
When this occurs the patient suffers excruciat- 
ing pain associated with a loud explosive noise 
in the ear; vertigo and nausea become marked 
and may be followed by shock and general col- 
lapse. Recovery is rapid but dull pain persists 
for a day or so and hearing loss for a longer 
period. 
The findings on examination vary with the 
amount of pressure differential to which the 
ear his been subjected. In the less severe cases 
there may be only the signs of a retracted mem- 
brane. These include increased brilliance of the 
105 AVIATION MEDICINE PRACTICE 
light reflex and backward displacement of the 
handle of the malleus. Increased prominence 
will be found of the handle of the malleus and 
especially of the short process and the anterior 
and posterior folds. Shrapnell’s membrane will 
be markedly retracted. 
In more severe cases there may be hyperemia 
of the tympanic membrane with small hemor- 
rhages into the membrane itself. The inflam- 
mation is most marked along the handle of 
the malleus and about the periphery. Depend- 
ing upon the severity of the trauma and upon 
the length of time the condition has been 
present, varying amounts of serous or bloody 
fluid may be present in the middle ear cavity. 
If the tympanic membrane has ruptured there 
will be bloody fluid in the external auditory 
canal. 
Aero-otitis chronic.—Chronic retraction of 
the membrana tympani is not uncommon. It is 
most frequently caused by lymphoid tissue in or 
about the pharyngeal orifice of the Eustachian 
tube. Less commonly it may be due to atresia 
of the canal or closure of the opening by scar 
tissue adhesions. The patients complain of 
stuffiness in the ears and are found to have 
a conductive type of hearing loss. These people 
almost always have difficulty in keeping the 
Eustachian tubes open when flying. 
Treatment.—Perhaps the most important 
item is prophylactic. Careful examination to 
insure patency of the Eustachian canals before 
selection for flight training is essential. Men 
with chronic inflammatory diseases of the nose 
or paranasal sinuses should be screened out. 
In the field men with upper respiratory in- 
fections should be grounded until the flight 
surgeon is satisfied that the mucous membranes 
of the nose and throat have returned to nor- 
mal, The vast majority of cases of aero-otitis 
occur among the lads who will not let a little 
head cold keep them on the deck. 
Active treatment is confined to the naso- 
pharynx and treatment of the underlying cause. 
The nose and nasopharynx are sprayed with 
one of the vasoconstrictors after which at- 
tempts should be made to inflate the middle 
ear. 
Equalization of the pressure may be ac- 
complished by the Valsalva maneuver, Politzer- 
ization or, when necessary, by means of the 
Eustachian catheter. Once the pressure in the 
middle ear is equalized the transudation of 
serum will cease and the structures will rapidly 
return to normal. The important thing is to 
keep the man on the ground until all signs of 
his upper respiratory infection have disap- 
peared. The chronic cases are frequently re- 
lieved by radium treatment to the lypmhoid tis- 
sue about the Eustachian tube orifice. X-ray 
therapy is also used and in some cases may be 
preferable to radium. 
Myringitis bullosa.—This is an inflammatory 
process confined to the outer layers of the 
drum and usually caused by infections of the 
canal or middle ear. It is characterized by the 
formation of vesicles in the drum membrane. 
It is commonly associated with influenza. If 
the middle ear is not involved the blebs subside 
spontaneously. Mild sedation and the instilla- 
tion of auralgan into the external canal suffice 
to control the discomfort. 
Otitis media.—In a chapter of this size such 
a comprehensive subject can only be touched 
upon. In 85 percent or more of such cases the 
condition is secondary to disease of the upper 
respiratory system. Perhaps congestion of the 
mucous membrane of the nasopharynx has 
caused obstruction of the orifices of the Eu- 
stachian tubes. Perhaps over zealous blowing 
of the nose has resulted in forcing infected 
material from the nasopharynx into the Eusta- 
chian tube itself. The sequence of events is 
roughly as follows: Obstruction of the Eu- 
stachian tube is followed by absorption of the 
air in the middle ear. The symptoms are stuffi- 
ness in the ear, loss of hearing (conductive 
type) and pain. If not treated at this stage 
transudation of fluid into the middle ear fol- 
lows. If infection follows the middle ear cavity 
will fill with pus. If untreated the tympanic 
membrane commonly ruptures and pus drains 
into the external canal. Once drainage is estab- 
lished resolution may proceed rapidly. The sulfa 
compounds and penicillin have proven wonder- 
fully efficacious in treating diseases of the mid- 
dle ear. The serious complications of mastoid- 
itis, sinus thrombosis, and brain abscess, so 
common before the advent of these drugs, are 
now rarely seen. 
106 Chapter 5. — OTOLARYNGOLOGY IN AVIATION MEDICINE 
Figure 5-9. 
THE NOSE AND PARANASAL SINUSES 
Anatomy.—The skeletal structure of the nose 
is composed partly of bone and partly of carti- 
lage. The small flat nasal bones and the piri- 
form crests of the maxillary bone give shape 
to the rigid upper part of the nose. The lower 
movable part is composed of two pairs of flat 
hyaline cartilage, the upper pair of which is 
continuous with the cartilage of the nasal sep- 
tum. Certain small accessory cartilages help 
give shape to the alae laterally. 
Internally the cavity of the nose is divided 
into roughly equal passages by the nasal sep- 
tum. Anteriorly the septum is cartilaginous 
107 AVIATION MEDICINE PRACTICE 
Figure 5-10. 
108 Chapter 5. — OTOLARYNGOLOGY IN AVIATION MEDICINE 
turbinate is inserted into a triangular space. 
Superiorly the wall is formed by the lateral 
wall and processes of the ethmoid while the 
lacrimal bone occupies a small space anteriorly. 
The posterior portion is completed by the per- 
pendicular portion of the palatine bone and 
the medial plate of the pterygoid process of the 
sphenoid. 
The lateral wall presents three or more shelf- 
like processes which hang down into the nasal 
cavity. These are called turbinates. These are 
thin shells of bone covered by mucous mem- 
brane which greatly increase the mucous mem- 
brane surface of the nasal cavity. The inferior 
turbinate is a separate bone and the largest 
of the turbinates. The middle and superior 
turbinate are outgrowths from the ethmoid 
labyrinth. 
The space below the inferior turbinate is 
called the inferior meatus. The nasolacrimal 
duct drains into this space anteriorly. The mid- 
dle meatus under the middle turbinate contains 
many important structures. The most import- 
ant of these is a long narrow groove, the hiatus 
semilunaris. Its importance lies in the fact that 
it drains all the anterior paranasal sinuses. 
These include the maxillary, frontal, and most 
of the ethmoid cells. A few ethmoid cells, known 
as the posterior ethmoids, drain into the su- 
perior meatus above the middle turbinate. 
The roof of the nasal cavity is formed by the 
cribiform plate of the ethmoid capsule. It is 
perforated by 20 or more small openings 
through which pass the terminal branches of 
the olfactory nerve. Posteriorly and inferiorly 
the nasal cavity opens into the nasopharynx. 
Above is the curved surface of the sphenoid 
bone. The sphenoid sinuses drain into a narrow 
slit between the sphenoid and ethmoid bones 
called the sphenoethmoid recess. 
The mucous membrane of the nose varies 
somewhat in different places. In the lower part, 
especially over the inferior turbinate, the mu- 
cous membrane is pseudostriatified columnar 
ciliated with many serous and mucous glands 
and a rich venous blood supply. In the upper 
straits of the nose the mucosa becomes non- 
ciliated and columnar in character. 
The blood supply to the nose comes from dif- 
ferent sources: from the ophthalmic branch of 
the internal carotid, the internal maxillary 
Figure 5-11. 
for the most part. The ploughshare shaped 
vomer bone, firmly attached to the maxillary 
and palatine bones which form the floor of the 
nose, is the bony support of the septum poster- 
iorly and superiorly, is filled by the perpendicu- 
lar plate of the ethmoid. These structures are 
covered by mucous membrane. 
Laterally the nasal wall presents an irregu- 
lar surface convoluted by the nasal turbinates. 
Inferiorly the lateral wall is formed by the 
superior maxilla. Just above this the inferior 
109 AVIATION MEDICINE PRACTICE 
Figure 5-12. Chapter 5. — OTOLARYNGOLOGY IN AVIATION MEDICINE 
branch of the external carotid and branches 
from the facial artery. The sensory nerves 
come from the first and second divisions of the 
Trigeminal nerve. 
The paranasal sinuses.—The paranasal sin- 
uses are divided into two groups, posterior and 
anterior. The dividing line is the attachment 
of the middle turbinate. Sinuses draining be- 
low the attachment of the middle turbinate are 
the anterior group. These include the frontal, 
maxillary and most of the ethmoid group of 
cells. The posterior group includes the few 
ethmoid cells which empty into the superior 
meatus and the sphenoid sinuses which drain 
into the spheno-ethmoid recess. 
The sinuses are formed as invaginations of 
mucous membrane from the nasal cavity with 
subsequent pneumatization of the bones for 
which they are named. The degree of pneumati- 
zation which takes place varies greatly in dif- 
ferent individuals. Even in the same indivi- 
dual the sinuses may not be of the same size 
on the two sides. There may be complete ab- 
sence of a sinus on one side with a well devel- 
oped cell on the opposite side. All sinuses must 
have an opening into the nasal cavity for 
ventilation and drainage. In about 40 percent 
of cases the maxillary sinus has one or more 
accessory openings. 
Blood supply.—Arterial supply is from the 
ophthalmic division of the internal carotid (an- 
terior and posterior ethmoid arteries) and the 
internal maxillary artery from the external 
carotid. The venous drainage is primarily to 
the pterygoid plexus via the sphenopalatine 
foramen, but there are also anastomoses with 
the ophthalmic and the anterior facial veins. 
Innervation.—The sensory nerves to the si- 
nuses are from the first and second division of 
the trigeminal nerve. 
Functions of the nose—Filtration, warming, 
and humidification of the air, preparing it for 
the lower air passages, are the primary func- 
tions of the nose. Olfaction is the next most 
important. The nasal cavity also acts as a 
resonating chamber in phonation. The nasal 
secretions possess a strong bacteriostatic prop- 
erty. The nose is also the origin and recipient 
of numerous reflex arcs. 
Filtration is accomplished in two ways. The 
vibrissae in the vestibules strain out coarse 
particles of dust or lint. In addition the entire 
mucous membrane surface of the nasal cavity is 
covered by a sheet of mucous which entraps 
foreign matter, including bacteria. By the ac- 
tion of the cilia this mucous sheet is continu- 
ously being moved backward toward the naso- 
pharynx where it is either swallowed or ex- 
pectorated. The cilia move the secretions at the 
rate of about 5 mm. per minute. It is constantly 
being replaced by the mucous glands of the 
mucous membrane. 
Inspired air is warmed by heat transfer 
from the mucous membrane, especially of the 
turbinates. It picks water vapor from the same 
source. If the mucous sheath were not being 
continuously replaced the membranes would 
become dry, the cilia would be inactivated and 
the principal functions of the nose destroyed. 
The functions of the paranasal sinuses are 
not so well known. It has been suggested that 
they reduce the weight of the head, that they 
act as reservoirs of warmed and humidified air, 
and that they act as resonators for the voice. 
Our primary interest in these cavities is to be 
sure that they are adequately ventilated and 
drained. They are lined with mucous membrane 
continuous with that of the nasal cavity proper. 
So long as the natural openings remain un- 
obstructed the cilia keep the sinuses empty and 
in a healthful condition. But it must be remem- 
bered that the sinuses are continuous with the 
nasal passages and that any condition involv- 
ing the nose may involve the sinuses also. 
DISEASES OF THE NOSE 
Malformations.—The size and shape of the 
external nose varies considerably in different 
individuals. In addition to racial and familial 
characteristics there are also deformities due 
to trauma. These are not considered disqualify- 
ing so long as they do not interfere with the 
functions of the nose. 
The common cold.—Colds are classified as 
bacterial, virus, and allergic. Chilling is an 
important predisposing factor. Other factors 
are fatigue, damp clothing, poor ventilation, 
nasal obstruction, or chronic infection of the 
mucous membrane of the nose and sinuses. 
Pathological findings include ischemia, hypere- 
mia, exudation, and extravasation of serum. AVIATION MEDICINE PRACTICE 
Later the secretions become thicker, more mu- 
coid and contain pus cells and surface epithe- 
lium. The congestion gradually subsides and the 
mucosa returns to normal. 
Complications of the common cold may in- 
volve the sinuses, the ear, the larynx and 
bronchi. The garden variety of headcold is 
the cause of more lost man-hours than any 
other disease. Its complications add greatly to 
this already formidable total. It is because of 
the complications of otitis and sinusitis that 
the flight surgeon must forever be educating 
his flight personnel of the dangers of flying 
when they have only “a little nose cold.” We 
have already discussed aero-otitis media. The 
common cold is the direct cause of this condi- 
tion in a great percentage of cases. It requires 
only a slight amount of congestion of the mu- 
cous membrane of the nasopharynx to occlude 
the pharyngeal opening of the Eustachian tube. 
Aerosinusitis.—Any obstruction to drainage 
of the sinuses results in absorption of the air 
in the sinus cavities, stagnation of the secre- 
tions in the sinus, followed by bacterial growth 
and the formation of pus. These conditions are 
associated with headache, tenderness over the 
sinus involved and usually a purulent nasal dis- 
charge. Like aero-otitis, aerosinusitis usually 
developed during descent from high altitudes. 
Congestion in the nose prevents air from enter- 
ing the sinus to equalize the increasing pressure 
of the atmosphere. Negative pressure increases 
in the cavity. The subject is aware of discom- 
fort followed by severe pain over the sinuses 
involved, usually above or below the eye. Re- 
turning to higher altitudes relieves the symp- 
toms. 
Treatment of diseases of the nose and sinuses 
has as its objective the return of adequate 
ventilation and drainage. The common cold 
we still treat symptomatically with vasocon- 
strictors, salicylates, and codeine. If the condi- 
tion is on an allergic basis the new antihistam- 
inic drugs are frequently of value. In suppura- 
tive conditions the sulfa compounds and anti- 
biotics are used. 
Allergy.—We can but mention this very im- 
portant subject. Personnel with nasal symp- 
toms of allergy (hayfever, polyposis, asthma) 
should be screened out during the selection of 
flight personnel. A careful family and person- 
al history coupled with the findings of the tell- 
tale pale boggy mucous membranes and/or 
the presence of nasal polyps should usually 
suffice to prevent these people from receiving 
flight instruction. 
Diseases of the nasal septum.—Many serious 
inflammatory conditions of the nose and sinuses 
are due to abnormalities of the nasal septum. 
The septum is rarely completely straight. Slight 
deviations and curvatures are not unusual. 
They are not important unless they interfere 
with the normal functions of the nose. Spurs 
or ridges in the lower portion may cause no 
inconvenience. Abnormalities higher up pres- 
sing on the middle turbinate may well obstruct 
the drainage of the anterior group of sinuses 
which empty into the hiatus semilunaris under 
the middle turbinate. 
Trauma to the nose is not uncommonly fol- 
lowed by hematoma of the septum. The ap- 
pearance is that of reddened masses occluding 
one or both nares, without other signs of local 
inflammation. If small, they may be allowed 
to absorb: more commonly, they are drained 
through a short incision in the dependent part 
of the mass. If they become infected a septal 
abscess may result. In addition to swelling, 
redness and edema of the septal mucosa, there 
is swelling, pain, and redness of the external 
nose. The abscess cavity is drained surgically 
and the opening maintained by a small drain 
until the abscess cavity is obliterated. 
Epistaxis.—Most nosebleeds occur from the 
area on the septum just inside the vestibule, 
known as Kisselbach’s area. Here the different 
arterial sources to the septum anastomose in 
a very vascular plexus. Trauma is perhaps the 
most common direct cause, but various diseases 
of the nasal membrane, violent blowing of the 
nose, sneezing, the inhalation of irritating dust 
and tumors all contribute. Epistaxis from the 
various types of cardiovascular disease are not 
frequently seen among flying personnel. 
The first step in treatment is to find the 
bleeding point. If the bleeding is anterior this 
is not a difficult matter. A good suction ap- 
paratus is a good deal of help in these cases. 
Frequently temporary control of bleeding can 
be obtained by compression of the nasal tip be- 
tween thumb and finger for a few minutes. The 
bleeding point may then be located and touched 
112 Chapter 5. — OTOLARYNGOLOGY IN AVIATION MEDICINE 
with strong silver nitrate, chromic acid, or the 
actual cautery. When the bleeding vessel can- 
not be localized it is frequently necessary to 
pack the nose, using an anterior or posterior 
pack, or both. Quite often the control of a 
severe nosebleed will try the patience, skill and 
ingenuity of the surgeon. 
Sinusitis.—Sinusitis may be present at all 
ages and respects neither season nor climate. 
The extent and persistence of the condition 
depends on two major physiological principles: 
ventilation and drainage. Treatment is always 
directed toward the improvement of aeration 
and drainage. The antibiotics and sulfa com- 
pounds are extremely helpful but drainage 
through natural or surgical openings must be 
established before one can expect a cure. 
Maxillary sinusitis.—In acute maxillary si- 
nusitis the predominant symptom is severe neu- 
ralgic pain referred to the cheek on the affected 
side, above the eye, or in the upper dental arch. 
There is tenderness to pressure over the in- 
volved sinus. As the condition becomes puru- 
lent the symptoms are aggravated. Sometimes 
the disease is secondary to a dental infection. 
A foul odor to the discharge is characteristic of 
dental infections. Headaches are common, par- 
ticularly when the natural ostium is occluded. 
Nausea, vomiting, and dizziness are not uncom- 
mon. There is usually discharge oozing from 
under the middle turbinate. 
Chronic maxillary sinusitis results when the 
acute condition fails to clear up under local 
treatment. The exudate becomes organized, the 
mucous membrane lining thickened and poly- 
poid. Polypoids growth may project into the 
middle meatus. When in doubt, irrigation of a 
suspicious appearing antrum aids in diagnosis. 
X-rays also are of value in doubtful cases. 
In the treatment of sinusitis, regardless of 
location, ventilation, and drainage are the two 
principles we try to promote. Shrinkage of the 
nasal membranes followed by mild suction is 
helpful in many cases. Steam inhalations, in- 
fra-red and diathermy all have their place. 
Once the acute condition has subsided irriga- 
tion of the antrum, either through the natural 
ostium or by means of a trocar under the lower 
turbinate, should be done periodically. If ir- 
rigation twice a week fails to show signs of 
improvement after a few weeks more radical 
measures become necessary. If the infection is 
dental in origin it is useless to attempt to cure 
the sinusitis while the offending tooth remains 
in place. 
Frontal sinus disease.—Symptoms: frontal 
pain and tenderness, sometimes referred to the 
temporal regions. The pain is aggravated by 
blowing the nose or coughing. Fever, leucocy- 
tosis, and generalized toxicity may be present. 
If the nasofrontal duct is obstructed fistulous 
tracts may develop. The bony floor of the sinus 
is quite thin and it is here that fistulae most 
commonly occur. But the pus may break into 
the ethmoid labyrinth, the nasal cavity, the 
orbit, or the cranial cavity, resulting in menin- 
gitis and brain abscess. Osteomyelitis of the 
skull is one of the most feared and dangerous 
complications. 
If the condition fails to respond to local treat- 
ment along with penicillin or sulfadizaine, sur- 
gical measures must be considered. The sim- 
plest and perhaps the safest approach is to tre- 
phine through the floor of the sinus. A rubber 
drain is sutured into the trephine opening and 
allowed to remain there as long as purulent 
drainage persists or until drainage into the 
nose is established. Fortunately most of cases 
respond to intranasal shrinkage, local heat, and 
the systemic use of penicillin. 
Esthmoid sinusitis.—The anterior ethmoid 
cells are in close proximity with the frontal and 
maxillary sinuses. Furthermore, all drain into 
the hiatus semilunaris, under the middle tur- 
binate. As a consequence it is seldom that one 
of these sinuses is diseased without some in- 
volvement of the others. Similarly, the poster- 
ior ethmoid cells may become infected from 
the sphenoid sinuses. As a group the ethmoids 
are probably more prone to infection than any 
of the other sinuses. In the acute form there is 
always a certain amount of involvement of the 
mucous membrane of the nose to complicate the 
picture. The symptoms are not clear cut but 
there is usually pain over the root of the nose, 
frontal headache, and nasal discharge. Transil- 
lumination and external pressure over the 
frontal and maxillary sinuses help to exclude 
them as the source of the discharge. A swollen 
upper lid is associated with frontal sinus 
disease, while swelling of the lower lid is 
characteristic of ethmoiditis. Swelling of both AVIATION MEDICINE PRACTICE 
lids indicates combined involvement. Proptosis 
of the eyeball may result from rupture of an 
ethmoid infection into the orbit. Movement of 
the eyes may be painful due to a periostitis 
about the pulley of the superior oblique muscle. 
The appearance of the middle turbinate is fre- 
quently helpful in diagnosis of ethmoid disease. 
In the early stages of the disease the middle 
turbinate is red and swollen. Later it may as- 
sume a polypoid appearance with markedly 
thickened mucous membrane. Pain is rare in 
the chronic form but there is a sensation of 
chronic dryness and secondary pharyngitis 
which causes discomfort. 
Treatment.—Conservative measures are tried 
first, shrinkage, suction, chemotherapy, and lo- 
cal heat. If indicated a submucous resection or 
fracture of the middle turbinate should be done 
to improve drainage from the middle meatus. 
Removal of the middle turbinate is a further 
measure to be followed by uncapping or exen- 
teration of the ethmoid cells. As a last resort 
the external ethmoid operation may become 
necessary as a lifesaving measure or because 
more conservative measures have been unsuc- 
cessful. 
Sphenoid sinus disease.—Inflammation of the 
sphenoid sinuses may be a direct extension 
from disease of neighboring sinuses, the nasal 
mucous membrane or from the nasopharynx. 
The ostia of the sphenoids open into the ethmo- 
sphenoid recess and may easily become ob- 
structed by swelling of the mucous membrane. 
The symptoms are variable but may consist of 
a deep boring headache, occipital or parietal, 
inability to concentrate, and associated with 
malaise and anorexia. In the chronic cases 
symptoms are so variable that certain writers 
have even described a characteristic pain in 
the arch of the foot. Symptoms may appear as 
ocular, aural, intracranial, mental or systemic 
manifestations. Pain is frequently referred to 
the mastoid area. Rupture may take place into 
the orbit, the ethmoids or the cranium with the 
development of a rapidly fatal meningitis. 
Cavernous sinus thrombosis is another feared 
complication. 
Examination of the nose and nasopharynx 
may show little or nothing. In chronic cases 
there is usually hypertrophy of the lateral lym- 
phoid bands in the pharynx with the presence 
of thick greenish tenacious exudate. Postrhin- 
oscopy may show the pus oozing downward 
from the ethmosphenoid recess on one or both 
sides. If orbital extension has occurred there 
may be proptosis, paralysis of the extraocular 
muscles with chemosis and swelling of both 
lids. Examination of the nose may show pus 
coming from above the middle turbinate. 
Treatment of sphenoid disease follows the 
pattern laid down for the other sinuses. Surgi- 
cal intervention must be done with extreme 
care because of the close proximity of the 
sphenoid sinus to the orbit, the optic nerve and 
chasm, the cavernous sinus, the meninges, the 
pituitary body and the internal carotid. As 
dehiscences may occur in the sphenoid bone 
any of the above may lie under the mucous 
membrane of the sphenoid sinus. 
Infections of the mouth and pharynx.—The 
pharynx is part of both the alimentary tract 
and the respiratory tract and is subject to 
lesions peculiar to both of these systems. The 
functions of the mouth and pharynx include 
mastication, salivation, the organ of speech and 
an important auxiliary respiratory system. Any 
lesion interfering with these natural functions 
is disqualifying. We can mention but a few of 
the more common conditions which not only 
cause discomfort to the patient but are an im- 
portant cause of lost man-hours. 
Acute pharyngitis.—As the pharynx is di- 
rectly continuous with the nose it is to be ex- 
pected that a certain degree of pharyngitis will 
accompany any infection of the upper respira- 
tory tract. It is a sufficient cause for grounding 
flying personnel. In addition to the local treat- 
ment to the nasal membranes, hot saline irriga- 
tions of the pharynx are comforting and bene- 
ficial. Analgesic drugs (codeine and aspirin), 
forced fluids, and specific chemotherapy should 
be used when susceptible organisms are found. 
Tonsillitis.—When the tonsils alone are dis- 
eased the term “tonsillitis” is applicable. But 
tonsillitis and “sore throat” are generally used 
synonymously. The infection of the tonsils is 
commonly only the local manifestation of a 
more general disturbance which has its original 
focus in some part of the upper respiratory 
tract. 
Acute peritonsillar abscess or quinsy sore 
throat is due to an extension of a tonsillar in- 
114 Chapter 5. — OTOLARYNGOLOGY IN AVIATION MEDICINE 
fection into the loose peritonsillar tissues with 
abscess formation. Seen early it can sometimes 
be absorted by prompt antibiotic or chemo- 
therapy. More commonly it requires surgical 
intervention. 
Tonsillitis chronic.—The question of whether 
or not tonsillectomy is indicated is constantly 
being met. It is well for the surgeon to have 
in mind a routine for the handling of these 
cases. A history of repeated attacks of ton- 
sillitis, or peritonsillar abscess, hypertrophied 
tonsils which obstruct breathing or deglutition, 
or tonsils suspected of being foci of infection 
are all adequate indications for tonsillectomy. 
Chronic pharyngitis.—This is usually due to 
irritation of the mucous membrane. An out- 
standing example is excessive smoking. An- 
other common cause is chronic drainage from a 
low grade sinusitis or chronic rhinitis. Elimin- 
ation of the underlying cause will frequently 
result in relief of symptoms. 
Infectious mononucleosis.—This is but one 
of the blood disturbances with findings refer- 
able to the pharynx. It is perhaps the most 
common. The symptoms are those of pharyn- 
gitis, tonsillitis, and influenza. In some cases 
fever persists for several weeks. Cervical aden- 
opathy and tenderness appear promptly. Dys- 
phagia is pronounced. The acute reaction usu- 
ally lasts about ten days followed by a slow 
convalescence. The blood picture is character- 
istic. It is assumed to be due to a filtrable virus, 
although the fusospirochetal organism is com- 
monly found in the ulcerations of the mucous 
membranes. Lymphocytosis, relative and abso- 
lute is about 50 percent greater than normal, 
with great variations in the total white cell 
count. A large percentage of the mononuclear 
cells are of the intermediary or large types. 
There is no specific treatment. 
QUESTIONS on OTOLARYNGOLOGY 
1. Discuss briefly the anatomy of the external audi- 
tory canal. 
2. Discuss factors to be considered in dealing with 
foreign bodies in the external auditory canal. 
3. Describe the normal tympanic membrane. 
4. Outline the management of a case of otomycosis 
including symptoms, findings, treatment and possible 
complications. 
5. Discuss the physiology of aero-otitis media. 
6. Describe the anatomy of the medial wall of the 
middle ear cavity. 
7. Describe the Eustachian tube. What is its func- 
tion? 
8. Discuss briefly the anatomy of the inner ear. 
9. Define: (a) oval window, (6) stapes, (c) en- 
dolymph, (d) nystagmus, (e) vertigo. 
10. A pilot flying on instruments goes into a spin 
to the right. Ignoring his instruments he recovers only 
to go into another spin to his left. Discuss physiology 
involved. 
11. Describe briefly: (a) Rinne test, (6) Weber test. 
12. Indicate the type of deafness caused by (a) 
foreign body in the external canal, (b) retracted tym- 
panic membrane, (c) tumor of auditory nerve, (d) 
acute labyrinthitis. 
13. Discuss the resonance theory of Helmhotz. 
14. Mouth breathing is detrimental to health. Why? 
15. While making a run on a target a divebomber 
pilot experienced sudden severe pain over right eye. Dis- 
cuss probable cause, prevention, and treatment. 
16. Discuss the functions of the nose. 
17. Discuss the importance of cilia of nasal mucous 
membrane. 
18. The tensor palati and levator palati muscles are 
important in flying. Why? 
19. An applicant for flight training has a deviation 
of the nasal septum which presses on a middle turban- 
ate. Explain why this is disqualifying. 
20. Explain why a man with conductive deafness 
hears better over the telephone than a man with per- 
ceptive type of deafness. 
BIBLIOGRAPHY 
1. Textbook of the Ear, Nose and Throat. Lederer 
and Hollender, F. A. Davis Company, Philadelphia, 
1947. 
2. Aviation Otolaryngology. Army Air Forces, 
School of Aviation Medicine, Randolph Field, Texas. 
3. Diseases of the Ear, Nose and Throat. Jackson 
and Jackson. Saunder, Philadelphia, 1945. 
4. Diseases of the Nose, Throat and Ear. Ballenger. 
Lea and Febiger, Philadelphia, 1943. 
115 CHAPTER 6 
THE CARDIOVASCULAR SYSTEM 
IN AVIATION MEDICINE * 
The human body is ordinarily regarded as a 
unit, both anatomically and functionally. As 
such it has great powers of adaptation to chang- 
ing environment and possesses a remarkable 
range of physical and mental capability. All 
this is made possible through the functional 
integrity of the millions of cells of which the 
body is composed. Most of these cells live es- 
sentially a unicellular existence, not unlike that 
of the simple forms of aquatic life, and re- 
quire a fluid environment of a relatively con- 
stant character. These conditions are met and 
maintained only through the continual and 
successful functioning of many physiological 
mechanisms not the least of which are the 
circulatory and lymphatic systems. 
The importance of the cardiovascular sys- 
tem in aviation rests on the fundamental fact 
that this system may be one of the limiting 
factors in man’s adaptation to the exacting 
and sometimes abnormal stresses encountered 
in flight. Thus, it becomes necessary to evalu- 
ate the cardiovascular status and reserve in 
terms of the type of flying to be done. If it 
is apparent that this reserve will be exceeded 
then an attempt should be made to alter the 
circumstances in flyer or plane, or failing this, 
to define the limitation. Theoretically at least, 
all persons can be classified with respect to 
their capacity to take part in flying activities. 
A consideration of various factors in flying 
which affect the cardiovascular system may 
well begin with the simple fact that piloting 
a plane ultimately depends on the human or- 
ganism and requires the continuous attention 
of the pilot. 
The immediate purpose of the circulatory 
system is to provide a continuous flow of blood 
to the capillaries and to regulate this flow in 
accordance with the ever-changing metabolic 
requirements. Food and oxygen are carried to 
the tissues and waste products are carried away 
to the lungs and kidneys. The circulation also 
plays an important role in heat regulation, in 
distributing various secretory products and in 
integrating many bodily functions. 
The cardiovascular system consists essenti- 
ally of the heart, arteries, veins and ramifica- 
tions of minute vessels, the smallest of which 
are the capillaries. These several divisions func- 
tion independently in varying degrees but the 
system as a whole is highly integrated, chiefly 
by means of nervous and chemical influences. 
THE HEART 
The heart may be regarded as a highly dif- 
ferentiated portion of the circulatory system. 
It consists of two main pumping units, each of 
which receives blood at low pressures and dis- 
charges blood at relatively high pressures. The 
chief function of the heart is to pump on all the 
blood it receives. The right heart receives ven- 
ous blood returning via the great veins and 
sends it into the pulmonary circuit. The 
oxygenated blood returning to the left heart 
is pumped onward into the systemic circuit. 
Although both left and right hearts contract 
simultaneously and are in other respects in- 
terdependent, yet each pumps blood at different 
pressures and is in other ways functionally in- 
dependent. This is clearly illustrated in the 
altered dynamics following predominent injury 
and failure of one ventricle. 
'Prepared by Captain Ashton Graybiel, (MC), USN. 
116 Chapter 6. —THE CARDIOVASCULAR SYSTEM IN AVIATION MEDICINE 
The cardiac cycle.—The cardiac cycle has 
been divided into two chief phases, ventricular 
systole and diastole. The systolic phase begins 
with the contraction of the ventricular muscu- 
lature and ends with the onset of relaxation. 
When the intraventricular pressure has risen 
slightly the mitral and tricuspid valves, which 
have already floated into position, are closed. 
Closure of these valves is mainly responsible 
for the first heart sound, there being an addi- 
tional sound element from the muscular con- 
traction of the ventricles. Intraventricular 
pressure rises rapidly until the semilunar 
valves are forced open. The ejection of blood 
proceeds rapidly at first, then slows after the 
major displacement of blood into the aorta has 
occurred. 
Diastole begins with the relaxation of the 
ventricles and ends with their contraction. At 
a heart rate of 75 a minute it occupies nearly 
twice as long a period of time as systole. The 
sharp fall in pressure in early diastole is quick- 
ly followed by the closure of the semilunar 
valves which prevents the regurgitation of the 
blood into the ventricles. The simultaneous 
closure of both aortic and pulmonary valves 
is responsible for the second sound which is 
usually of high pitch and snapping in char- 
acter. As the intraventricular pressure falls 
below that of the auricles the A-V valves open 
and blood flows from auricle to ventricle. This 
flow is rapid at first because of the volume of 
blood stored in the auricles and is associated 
with the physiological third sound which is 
sometimes heard. There follows a period of 
slower ventricular filling until the final aug- 
mentation due to auricular systole which term- 
inates the period of ventricular diastole. 
The intrinsic control of the heart heat.— 
The heart has its own system of specialized 
conduction tissue consisting of the sinoauricu- 
lar (S-A) and auriculo-ventricular (A-V) 
nodes, the bundle of His and its branches and 
the Purkinje network. The S-A node or pace- 
maker is an elongated mass of delicate neuro- 
muscular fibers lying along the sulcus termin- 
alis at the junction of the superior vena cava 
and the right auricle. The A-V node lies in the 
posterior interauricular sulcus near the orifice 
of the coronary sinus. From it fibers arise 
which cross the A-V septum, pass forward in 
the lower part of the membraneous septum 
where they separate into left and right 
branches. These fibers are called the bundle 
of His and form the only direct muscular con- 
nection between auricles and ventricles. The 
left and right bundle branches continue down 
into the left and right ventricle where, after 
numerous subdivisions, they terminate in deli- 
cate strands called Purkenje fibers, which are 
distributed to the muscle fibers of the ven- 
tricles. 
The excitation stimulus arises in the S-A 
node (pacemaker) from whence it spreads 
rapidly across the auricles stimulating the mus- 
cle fibers to contract. The auricular contrac- 
tion which follows also spreads wavelike across 
the auricles in peristaltic fashion, and, in the 
case of the right auricle, directs the flow of 
blood away from the great veins toward the 
ventricle. When the excitation wave reaches 
the A-V node it discharges the stimulus build- 
ing there and is led by way of the specialized 
conduction tissue to all or nearly all of the 
ventricular muscle fibers. This results in simul- 
taneous activation of the ventricular muscu- 
lature and hence effective contraction. The 
heart, in common with other muscular tissues, 
readily displays electrical activity when stimu- 
lated and a record of the potential variations 
associated with the spread of the excitation 
wave is observed in the electrocardiogram. 
The most important feature of cardiac physi- 
ology is concerned with muscular contraction 
and the law of the heart. The law of the heart, 
or Starling’s Law, simply states that within 
physiological limits the work capacity of the 
heart varies with the diastolic volume. In other 
words, the strength of contraction increases 
with increased stretch and lengthening of the 
muscle fibers. It is chiefly by virtue of this 
fact that the heart can readily adjust to vari- 
able loads placed upon it either through varia- 
tions in the venous return or through altera- 
tions in arterial pressure. 
Let us assume for the moment that the 
venous return to the heart is increased but 
that the heart rate remains constant. The ve- 
nous pressure is increased, more blood will enter 
the ventricles during diastole, the muscle fibers 
are stretched to greater length and the ven- 
tricles will contract on a larger diastolic vol- 
117 AVIATION MEDICINE PRACTICE 
ume. This will result in a more forceful systolic 
contraction and a larger volume of blood will 
be displaced under a greater pressure. The 
reverse occurs when the venous return is de- 
creased. 
Again let us assume that the venous return 
to the heart and the heart rate remain constant 
but that the arterial pressure is suddenly 
raised. The subsequent contraction will not be 
sufficiently forceful to expel all of the blood 
against the increased pressure and a portion 
will remain in the ventricle. To this will be 
added the- usual inflow during the next dias- 
tolic period. This results in an increased dias- 
tolic volume, increased diastolic length of mus- 
cle fiber, and as a consequence, a more forceful 
systolic contraction. In a few beats the ad- 
justment will be made to the increased arterial 
pressure and the initial stroke volume will be 
regained. 
The work of the heart.—It has been shown 
that the cardiac output in the same individual 
varies greatly depending on the circumstances 
and that, under similar (basal) conditions, the 
cardiac output in different individuals is a 
function of the surface area. The cardiac index 
has been defined as the cardiac output per 
square meter of body surface and has found 
that in young healthy persons under basal con- 
ditions it is 2.2±0.2. 
Some idea of the amount of blood the heart 
pumps over a period of time is readily gained 
from cardiac output estimations. Assuming 
that the cardiac output averages 5 liters per 
minute during the 24 hours of the day, then 
left and right would pump 14,400 liters, or 
about 75 barrels of blood. 
The great reserve power of the heart is 
illustrated by the enormous increase in cardiac 
output as a result of exercise. The cardiac 
output of an average sized man at rest is in 
the neighborhood of four liters a minute and 
during strenuous exercise may rise to 30 liters 
a minute and has been measured as high as 
37.3 liters a minute. Inasmuch as the right 
heart pumps as much as the left these figures 
should be doubled when considering the total 
output. 
Heart failure.—Heart failure may occur sud- 
denly or gradually as a result of disease or 
functional disturbance. The lesser degrees are 
manifest only by a decrease in reserve while 
in the advanced stages the heart may be un- 
able to pump on all the blood returning to it 
even with the body at rest. In the early stages 
of heart failure, when that organ is put under 
a strain, compensation is effected by a relative- 
ly greater increase in diastolic volume than 
normally. In other words, with increasing de- 
grees of heart failure the muscle fibers must 
stretch more and more to provide the same 
force of contraction. Eventually a limit is 
reached beyond which further stretching of 
the fibers results in a decreased ability of the 
heart to pump blood and the terminal stage 
of heart failure ensues. 
The nervous control of the heart rate.—The 
heart rate is under the immediate control of 
the pacemaker (S-A node), the rythmical dis- 
charges of which are under the influence of the 
sympathetic (accelerator) and vagus (inhibi- 
tory) systems with “centers” located in the 
floor of the fourth ventricle. These centers can 
be influenced both reflexly and by the higher 
centers. The lability of the heart rate in re- 
sponse to emotional factors is well known. 
Other ways in which the heart rate can be re- 
flexly affected include the following: (1) when 
rate is slowed and vice versa. This is some- 
times referred to as Marey’s Law. (2) When 
the pressure in the aorta is increased the heart 
the pressure in the carotid sinus is increased 
the heart rate is slowed and vice versa. (3) 
When the pressure in the right auricle and 
great veins is increased as a result of increas- 
ing venous return there is acceleration of the 
heart rate. This is often referred to as the 
Bainbridge reflex. (4) Somatic impulses may 
also reflexly affect the heart rate. 
In the healthy man at rest the heart rate 
is usually between 50 and 80 a minute but 
these limits may occasionally be exceeded. 
Pulse rates as slow as 40 a minute have been 
observed in athletics but rates much above 
80 should be regarded with suspicion if the 
subject is mentally and physically at rest. Emo- 
tional stimuli may increase the rate up to 140 
or even higher, and during exercise the rate in 
an adult may reach 190. Abolishing the vagus 
impulse with atropine may cause an increase 
in rate up to 150 or slightly higher. 
118 Chapter 6. —THE CARDIOVASCULAR SYSTEM IN AVIATION MEDICINE 
THE PERIPHERAL VESSELS 
The aorta and large elastic arteries.—The 
aorta, and to lesser extent other large arteries, 
are relatively thin-walled and contain a large 
amount of elastic tissue. With each systolic 
discharge these vessels are distended and more 
blood is temporarily stored than is immedi- 
ately passed onward to the smaller arteries. 
During diastole the arteries contract to their 
original size by virtue of their elasticity and 
this presses forward the blood stored during 
systole. Thus the intermittant flow of blood 
from the heart is transformed into a continu- 
ous but pulsitile flow in the periphery. In ad- 
dition, special areas in the arch of the aorta 
and at the bifurcation of the carotid arteries 
contain nerve endings which are sensitive to 
stretching of the vessel walls. 
The large muscular arteries.—Arteries such 
as the brachial and femoral have a strong 
median coat of circularly arranged muscle 
fibers which, when stimulated, can greatly 
reduce the size of the lumen. By such altera- 
tions in caliber the flow of blood to a particu- 
lar organ or region may be markedly increased 
or decreased. This differential distribution of 
blood is initiated locally, probably by chemical 
influences and augmented by reflex vasodilata- 
tion in the active areas and vasoconstriction 
in other areas. 
The arterioles.—The arterioles are minute 
arteries averaging about 0,2 mm, in outside 
diameter. The muscular coat, relative to the 
size of the lumen, is more strongly developed 
than in any other order or size of vessel. They 
are well supplied with vasomotor nerves and 
are normally subject to tonic vasoconstrictor 
impulses. The arterioles are the site of the 
greatest degree of peripheral resistance and 
hence the steepest fall in pressure gradient. 
This helps to maintain the arterial blood pres- 
sure and, at the same time, to protect the capil- 
laries from high blood pressures. The immedi- 
ate cause of essential hypertension is to be 
found in an abnormal degree of vasoconstric- 
tion of the arterioles. 
Capillaries.—The capillaries consist of single- 
walled endothelial tubes and are rightly repre- 
sented as forming the keystone of the circula- 
tery system because here only are the vascu- 
lar walls sufficiently thin to permit adequate 
interchange of fluids and gases between blood 
and tissues. Each organ contains the number 
of capillaries necessary for its maximum func- 
tioning needs but during rest many or most 
of the capillaries are closed. If most of the 
capillaries were dilated at the same time they 
would contain the entire volume of blood in 
the body. Capillary tonus is largely, if not 
entirely, under independent control and is regu- 
lated by local conditions. The pressure in open 
capillaries is usually low but varies greatly; 
the range being from a few to 50 or more mm. 
mercury. A closed capillary may remain so 
against a pressure as great as 110 mm. mer- 
cury. 
Veins.—The blood, after passing through the 
network of capillaries and other minute ves- 
sels, is again collected into larger vessels, the 
veins, and returned to the heart. This narrow- 
ing of the vascular bed increases the rate of 
flow but the veins have thinner walls and 
much larger capacity than the corresponding 
arteries. They are readily distended with blood 
and collapse easily when emptied. The veins 
are in a state of tonic contraction under the 
control of the vasomotor center and also re- 
spond to local physical and chemical stimuli. 
Veins with a diameter of one mm. or greater 
have valves so arranged that the contained 
blood can only move centrally. These valves 
are best developed in veins of the extremities 
and are absent in the large veins in the ab- 
dominal cavity, the veins of the head and neck 
and in certain other veins. 
Venous return to the heart.—There are a 
number of factors which aid in returning the 
venous blood to the heart, the most important 
of which are the following: (1) The pressure 
and volume flow of blood in the capillaries. 
(2) Valves which direct the blood centrally. 
(3) Muscular tonus and the messaging effect 
of active muscles. (4) The pressure gradient 
in the abdominal cavity; the intestinal contents 
are thought to act like a fluid mass and con- 
sequently the pressure on the veins is much 
higher in the lower than in the upper part of 
the abdomen. (5) The aspirating effect in the 
119 AVIATION MEDICINE PRACTICE 
thorax produced by inspiration. (6) Gravity 
assists in the return of blood from the upper 
part of the body. 
THE CORONARY CIRCULATION 
The coronary circulation is unique in several 
respects and requires special consideration. 
About 5 percent of the cardiac output flows 
through the two coronary arteries which sup- 
ply the heart. 
A large but varying proportion of blood pas- 
ses through the capillaries and is returned to 
the right auricle by way of the coronary sinus. 
A small proportion of the blood passing 
through the capillaries returns to the heart 
chambers directly via the Thebesian veins. Also, 
blood in the coronary arteries may reach the 
heart cavities directly via small anastomotic 
vessels and by way of the myocardial sinu- 
soids. 
During systole, as the heart muscle con- 
tracts on its contents, intramuscular pressure 
is raised to the point where coronary flow is 
greatly reduced. According to Wiggers, in- 
tramural pressure never equals the aortic and 
“the myocardium receive approximately three- 
fourths as much blood during systole as dur- 
ing an equivalent interval of early diastole but. 
of course, much less than during the entire 
period of diastole on account of its greater 
duration.”' 
The single most important factor in deter- 
mining coronary flow in the normal heart is the 
pressure of blood in the aorta, particularly 
mean pressure. Other factors of importance 
are the effects of vasomotor and local chemical 
effects. The coronary vessels are thought to 
be under tonic vagal control and to dilate as 
a result of vagal inhibition or sympathetic 
stimulation. Thus, there is commonly a greater 
tendency for the coronary arteries to dilate 
rather than to constrict. There is both clinical 
and laboratory evidence that the coronary ves- 
sels are dilated as a result of muscular meta- 
bolites and anoxia. 
THE PORTAL CIRCULATION 
Blood, after passing through the minute ves- 
sels of the spleen and most of the gastrointes- 
tinal tract, is not returned directly to the heart 
but just passes through the liver and hence 
through two sets of capillaries. The capacity 
of the portal system can vary a great deal and 
because of this the liver may function not only 
as a regulator of venous return but as a reser- 
voir when the venous pressure in the right 
auricle is raised because of heart failure or 
other reason. 
MECHANISMS CONTROLLING THE 
CIRCULATION AS A WHOLE 
Although the regulation of the various divi- 
sions of the circulatory system have certain 
distinctive features, the system as a whole func- 
tions as a unit by means of various coordinating 
influences. The degree of integration is such 
that alteration of the circulation in one part 
of the system and in its regulatory mechan- 
ism, evokes responses in other parts in order 
to distribute the strain and to maintain the 
highest efficiency. The most important regula- 
tory mechanisms are concerned with the main- 
tenance of proper arterial and venous pressures. 
This is effected chiefly by means of true en- 
dovascular proprioceptive reflexes which origin- 
ate in the great veins and right auricle, the 
aorta, and the carotid sinuses, and become effec- 
tive after passing to the cardiac and vasomotor 
centers in the medulla. Chemical stimuli be- 
come generally effective after acting locally, 
and psychic stimuli after acting on the cardiac 
and vasomotor centers. 
In aviation, unique stresses are applied to 
the cardiovascular system. Inasmuch as piloting 
aircraft is dependent upon the constant atten- 
tion of the pilot, the functional integrity of 
the cardiovascular system must not be impaired 
even for a moment. The stress applied must 
not exceed the ability of the cardiovascular 
system to compensate. Certain types of failure 
of the peripheral circulatory system which 
would be regarded as of minor consequence in 
ordinary life might prove diastrous if they oc- 
curred in the pilot of a modern high perform- 
ance military aircraft. It is therefore incum- 
bent upon the flight surgeon or aviation medical 
examiner to exclude from an aviation career 
those applicants with structural and functional 
defects. 
In aviation the stresses applied to the cardio- 
120 Chapter 6. —THE CARDIOVASCULAR SYSTEM IN AVIATION MEDICINE 
vascular system are related directly to speed, 
acceleration, and maneuverability of aircraft. 
Should the stress applied exceed the critical 
level of cardiovascular adaptability of the in- 
dividual, cardiovascular failure, either central 
or peripheral will result. The functional integ- 
rity of the pilot is lost or embarrassed and a 
hazardous situation is immediately precipitated. 
It is apparent then that the flight surgeon 
must familiarize himself witth those stresses 
which are rather peculiar to aviation in order 
that he may correctly evaluate the individual’s 
ability to withstand these forces. Certainly, 
three specific problems encountered in aviation 
are worth close scrutiny. 
Acceleration.—Forces resulting from change 
in velocity or change in direction of motion 
may produce serious disturbances of circula- 
tion. These forces are the forces of acceleration 
and may be the result of (1) lineal, (2) angu- 
lar, or (3) radial velocity changes. 
Lineal acceleration is that force which is a 
result of change in velocity in a straight line 
path. It is manifested during take-off, at the 
moment a pilot’s parachute opens, during bail- 
out and at the moment of ejection in seat- 
ejection devices. More importantly, it is the 
main force acting in a crash. 
The forces of lineal acceleration are usually 
high in magnitude, particularly in crashes, but 
active during a short time interval. At present, 
lineal acceleration exerts very little effect on 
the cardiovascular system either centrally or 
peripherally. It may in the future, however, 
be a much more important factor which will 
require consideration in the design of prone 
position aircraft or in aircraft having power- 
ful seat-ejection devices. 
Angular acceleration may be defined as 
change in angular velocity in unit time. It 
is the force encountered in skidding turns 
and in spins. The effect of the forces of angu- 
lar acceleration upon the cardiovascular sys- 
tem is only of very slight consequence. Disor- 
ientation due to stimulation of the receptor or- 
gans of the inner ear is a very real threat to 
the functional integrity of the pilot and is the 
principle effect of angular acceleration. 
The forces generated by changes in direc- 
tion of motion are due to radial acceleration, 
which may be positive or negative in character. 
The forces acting in negative acceleration 
are along the long axis of the body from feet 
to head. These are the forces experienced dur- 
ing outside loops, inverted spins, inverted snap 
rolls, etc. Inasmuch as the forebearers of the 
human organism were not required to exist in 
an inverted state, adaptive mechanisms were 
only feebly developed to assist man in return- 
ing blood from the head. When placed in the 
inverted position man’s vascular system com- 
pensates very poorly. The additive strain of 
even slight accelerative forces applied in this 
position quickly overcomes the primitive mech- 
anisms and their feeble response toward 
homeostasis with resultant pooling of blood 
within the cranium. This then may be spoken 
of as a rather special type of peripheral vascu- 
lar failure which results in “red out,” uncon- 
sciousness, and even intracranial hemorrhage 
depending upon the magnitude of the forces 
and the duration of their application. There 
are manifested individual variations in ability 
to withstand negative accelerative forces. How- 
ever, even in those individuals who show some 
resistance to these forces, the total stress re- 
quired to produce symptoms is of a minor 
magnitude. 
Positive accelerative forces act from the head 
toward the feet and are encountered in sharp 
pull-outs, steeply banked turns and many acro- 
batic maneuvers. As previously stated, there 
are many factors operative in returning the 
blood from the lower extremities to the heart 
and which act to prevent pooling of blood in 
the periphery. The summation of these forces 
represents the total effective force acting to 
return the blood to the heart. 
During the application of positive accelera- 
tive forces, the hydrostatic pressure of the 
blood column may exceed the total force of 
these compensating mechanisms and reflexes 
with resultant pooling of blood in the extremi- 
ties, decreased venous return resulting in de- 
creased cardiac output and cerebral anoxemia 
with “blackout,” unconsciousness, convulsions, 
and finally death, again depending on time-in- 
tensity factors. Once more, it is to be noted 
that the primary failure is of the peripheral 
vascular system rather than the heart itself. 
121 AVIATION MEDICINE PRACTICE 
It is a well recognized fact that there are 
wide individual variations in ability to with- 
stand accelerative forces. Thus, we find indivi- 
duals who show marked resistance to the stress 
of positive acceleration. Again, there are indi- 
viduals who manifest marked susceptibility to 
the forces of positive acceleration. Furthermore, 
it has been shown that variations in susceptibil- 
ity may occur within the same individual from 
time to time. It is apparent, therefore, that sus- 
ceptibility to the stresses of positive acceleration 
is a function of the efficiency of the peripheral 
vascular system. Any factor which tends to 
decrease the efficiency of the peripheral com- 
pensatory mechanisms will result in a lower 
tolerance to positive acceleration. What then 
is the role of the flight surgeon in combating 
these accelerative forces? It is incumbent on 
us to develop more protective mechanisms 
which will guard against or prevent failure of 
the peripheral vascular network. The develop- 
ment of highly efficient antiblackout suits 
should be a prime research topic. The research 
workers must devise aircraft in which the 
position of the pilot may be such as to minimize 
the stresses of acceleration. 
The flight surgeon in practice must recognize 
those individuals showing marked susceptibility 
to positive acceleration. It is further necessary 
that he recognize those whose susceptibility 
is organic in nature, i.e., those showing true 
postural hypotension and other peripheral vas- 
cular states as distinct from those manifesting 
a transient decrease in efficiency of peripheral 
adaptive mechanisms as a functional result. It 
has been shown that with severe fatigue, fol- 
lowing severe sunburn, during convalescence 
from a disease and following prolonged gastro- 
intestinal upsets, the efficiency of peripheral 
vascular adaptive mechanisms may decrease 
alarmingly. Obviously, those individuals whose 
susceptibility is organic in nature should be 
prevented from flying military aircraft per- 
manently. Furthermore, it is necessary to 
ground, at least, those showing a functional 
decrease in peripheral vascular efficiency. 
Decompression sickness.—When the atmos- 
pheric pressure is sufficiently and quickly re- 
duced symptoms may arise as a result of the 
formation of gas bubbles within the body. This 
bubble formation, of course, takes place in ac- 
cordance with the laws governing the solubility 
of gases. Thus, at sea level the tissues are 
saturated with gases, chiefly nitrogen, oxygen, 
and carbon dioxide. When the atmospheric pres- 
sure is rapidly reduced, the tissues become 
supersaturated with these gases with the re- 
sultant formation of small bubbles composed 
largely of nitrogen. The symptom complex 
produced by localization of these bubbles in 
certain sites is spoken of as decompression 
sickness. The symptoms produced are mainly 
referred to the joints and extremities. 
On occasion, however, an individual will man- 
ifest all the symptoms of peripheral vascular 
failure, e.g., paleness, perspiration, syncope, a 
precipitous fall in blood pressure and either a 
tachycardia or a bradycardia. Further studies 
on these individuals have shown that the heart 
itself is unaffected. The failure, then, is pri- 
marily within the peripheral vascular system. 
The fundamental precipitating factor in this 
loss of vascular efficiency has not yet been 
determined. The localization of gas bubbles 
within the medulla contiguous to the vasomotor 
centers has been hypothecated as a possible 
etiological factor. Amplification of this point 
awaits further investigative study. 
Anoxia.—Because it is known that even the 
normal heart will dilate and fail if the oxygen 
supply is sufficiently reduced it has been com- 
monly believed that even moderate degrees of 
anoxemia will not only affect the normal func- 
tioning of the cardiovascular system but ac- 
tually damage the heart as well. Whether or 
not such damage may occur under the condi- 
tions met with in civil or military aviation 
deserves careful consideration. 
In military aircraft most of the flying is 
still done at relatively low altitudes but some 
is done at elevations between 35,000 and 40,000 
feet. At 40,000 feet the alveolar oxygen tension 
of a pilot inhaling pure oxygen corresponds to 
that of a pilot breathing air at 11,000 feet. 
From a practical standpoint it is nearly im- 
possible to prevent slight leakage when using 
an oxygen mask so that the degree of anoxemia 
usually exceeds the theoretically calculated 
amount. 
Because of the constant presence of some de- 
gree of anoxemia encountered in flight, it is 
122 Chapter 6. —THE CARDIOVASCULAR SYSTEM IN AVIATION MEDICINE 
necessary that the flight surgeons know and 
understand the effects of oxygen deprivation 
upon the cardiovascular system. 
Symptoms.—Healthy subjects during high 
altitude flight or exposed to low oxygen ten- 
sions in the laboratory rarely complain of sym- 
ptoms directly referable to the heart. The 
dyspnea which may be noticed is not severe 
and is due to stimulation of the peripheral 
chemoreceptors by hypoxia and is not a sign of 
heart failure. Pain of cardiac origin is never 
noticed and palpitation very rarely. 
Pulse rate.—Of all the circulatory changes 
iue to diminished oxygen tension, acceleration 
of the heart rate has been studied the most. 
With successive decreases in oxygen tension the 
rate continues to increase slowly but the in- 
crease in rate is not marked until extreme de- 
grees of anoxemia are reached. 
Blood pressure.—The changes in blood pres- 
sure due to increasing hypoxia follow several 
fairly well recognized patterns. In the majority 
of healthy persons there is little change until 
the oxygen in the inspired air has fallen to 
low levels. Then there may occur a gradual rise 
in systolic and fall in diastolic pressure with 
consequent increase in pulse pressure. In sus- 
ceptible persons exposed to moderate degrees 
of oxygen deficiency fainting may occur and 
there is a sudden fall in both systolic and dias- 
tolic pressure and an increase in pulse rate. 
This fainting reaction is in the nature of peri- 
pheral vascular collapse and is caused by cere- 
bral anoxemia and is not due to heart failure. 
In a few subjects there is little change in 
blood pressure till unconsciousness supervenes. 
It is only at this stage of “crisis” that the 
fall in blood pressure may be directly attribut- 
able to a failing heart. 
Cardiac output.—The cardiac output in- 
creases in healthy persons at rest under condi- 
tions of moderate hypoxia. This increase may 
be regarded as a compensatory or adjustment 
mechanism. With marked decreases in oxygen 
tension the cardiac output may fall as a direct 
result of cardiac anoxia but this stage is never 
reached under present flight conditions. More 
studies along this line are necessary before 
the relationship between anoxia and cardiac 
output is properly understood. 
Heart size.—It is now quite generally agreed 
that the normal heart, if the subject is at rest, 
does not dilate even with greatly lowered 
oxygen tensions. This conclusion is borne out 
by animal studies in which it is shown that 
cardiac dilation does not begin until the oxygen 
saturation of arterial blood has fallen to about 
50 percent or below. 
The electrocardiogram and hypoxia.—The 
electrocardiographic changes have been studied 
during actual flight conditions as well as under 
conditions stimulating high altitudes in the 
laboratory. In healthy persons these changes 
consist of progressive lowering of the S-T seg- 
ments and T waves with increasing hypoxia. 
Occasionally the T waves may be diphasic el- 
even slightly inverted. 
We know that there are many causes of low- 
ering of the T waves which do not damage the 
heart and there is no good proof that the elec- 
trocardiographic alterations just described in- 
dicated myocardial damage. 
In normal persons the symptoms which may 
appear under conditions of civil or military 
aviation and the associated changes in circu- 
latory dynamics do not indicate heart failure 
but may be considered adjustments or com- 
pensatory reactions to the oxygen deficiency; 
the most trustworthy evidence supports the 
view that the normal heart is not damaged. 
In healthy individuals it is believed that the 
brain suffers from anoxemia long before the 
heart does, the latter enjoying a kind of en- 
forced protection. The peripheral circulatory 
collapse that may occur in susceptible indi- 
viduals even at relatively low altitudes depends 
primarily on a deficient supply of oxygen to 
the central nervous system. 
Heart disease and hypoxia.—In turning from 
a consideration of the normal to the diseased 
heart we find good evidence that heart failure 
may be precipitated as a result of experimental- 
ly induced anoxemia in patients with heart 
disease. It would be strange indeed if this were 
not true. The surprising thing is that so few 
instances of heart failure have been reported 
and that those instances are restricted to pa- 
tients with severe disease. Pain of cardiac 
origin has been observed occasionally as well 
as less specific symptoms of heart failure such 
123 AVIATION MEDICINE PRACTICE 
as marked dyspnea, weakness, and collapse. 
Congestion of the lungs has been noted occa- 
sionally and arrhythmias rarely. In addition to 
these symptoms and signs evidence of heart 
failure is seen in the increased circulation time, 
decreased cardiac output, increased venous pres- 
sure, and in the marked electrocardiographic 
changes which may occur. 
In summary, it is evident that the degree 
of anoxia intentionally encountered under 
present flying conditions in civil and military 
aviation does not damage the normal heart. 
The changes observed in the electrocardiogram 
do not indicate heart injury; they are probably 
due in part to the alkalosis resulting from 
overventilation. 
However, it is clear that heart failure of the 
congestive or anginal type has been produced 
in patients with severe degrees of heart disease 
on exposure to oxygen tensions simulating al- 
titudes of 14,000 to 20,000 feet or higher. 
It is thus apparent that in aviation certain 
rather profound specific stresses may be ap- 
plied to the cardiovascular system. Further- 
more, it is obvious that the effect of these 
stresses is dependent upon the integrity of the 
heart and the vascular system. Thus, the stress- 
es normally encountered in flying, although 
affecting the normal cardiovascular system to 
some extent do not seriously embarrass it as a 
rule. However, as has been shown, these stress- 
es applied to a faulty cardiovascular system 
may produce serious embarrassment and failure 
either of the heart itself or of the peripheral 
compensatory mechanisms. The flight surgeon 
must therefore be acutely conscious not only 
of the global effect of these stresses but also 
of the exact cardiovascular status of the pilot. 
It is necessary that he recognize those func- 
tional states which may produce cardiac failure 
as well as the various manifestations of organic 
heart disease. Of equal importance is the rec- 
ognition of functional states of reduced pheri- 
pheral vascular efficiency as well as those dis- 
ease states which produce inherent vasomotor 
instability. 
It is necessary then to weigh the global effect 
of the stresses to be encountered against the 
cardiovascular system of the individual under 
consideration and from such examination to de- 
termine whether that individual is a good can- 
didate for aviation. 
BIBLIOGRAPHY 
1. Abramson, D. I. Vascular Responses in the Ex- 
tremities of Man in Health and Disease. Univ. of Chica- 
go Press; 1944. 
2. Best and Taylor Physiological Basis of Medical 
Practice., Third Edition. Williams and Wilkins; 1943. 
3. Graybiel, Ashton A Consideration of the Effects 
of Oxygen Lack of the Cardiovascular System from 
the Viewpoint of Aviation. Journal of Aviat. Med., 12, 
1941. 
4. Graybiel, Ashton and McFarland, Ross A. The 
Use of the Tilt Table in Aviation Medicine. Journal 
Aviat. Med.; 12, 1941. 
5. Graybiel, Ashton, Patterson, John L. Jr., Packard, 
John M. Sunburn as a Cause of Temporary Lowering 
of Blackout Threshold in Flyers. Journal Aviat. Med. 
19, 1948. 
6. Grollman, Arthur, The Cardiac Output of Man 
in Health and Disease. Charles C. Thomas, 1932. 
7. Howell, W. H. Textbook of Physiology. Edited by 
John C. Fulton, 15th Edit. W. B. Saunders, 1946. 
8. Levine, S. A. Clinical Heart Disease 3rd Edit. 
W. B. Saunders, 1945. 
124 CHAPTER 7 
AVIATION PSYCHOLOGY * 
Aviation psychology received its start during 
the first World War. Early beginnings were 
found in France and Italy, where in 1916 and 
1917 respectively, standards were set for ac- 
ceptance of candidates for flight training. By 
the end of the first World War, psychological 
as well as physical procedures were widely 
used by the nations involved, in the acceptance 
and rejection of aviation candidates. It has 
been pointed out in a report by the Committee 
on Selection and Training of Aircraft Pilots of 
the National Research Council that: 
“Attention centered upon psychological meth- 
ods in selection for the following reasons; (1) 
Despite selection on the basis of rigid physical 
examinations a large percentage of the trainees 
washed out; (2) among those who graduated 
from flight training courses some required up 
to twice as much training as others; (3) even 
after graduation there were large individual 
differences in proficiency; (4) accidents were, 
in many instances attributed to psychological 
defects in the pilot; and finally, (5) there were 
many cases of nervous breakdown among flyers. 
“It has also been pointed out that all of the 
psychological work done during the first World 
War fell under one or more of the following 
categories: tests of psychomotor processes in- 
cluding measurement of the speed of simple 
reactions and complex reactions and complex 
reaction tests; combinations of psychomotor 
and intellectual tests; investigations of sensory 
processes; personality observations; and inves- 
tigations of psychological functions under low 
oxygen tension.” 
In spite of this beginning, however, aviation 
psychology came to an end soon after World 
War I. Even in the United States, in spite of 
the growth of aviation and the establishment 
of a School of Aviation Medicine, research by 
psychologists in the field of aviation was almost 
totally discontinued. The most important de- 
velopments during the next fifteen years are 
traced in the report quoted above: 
“Some studies of high altitude effects were 
carried out; an improved personality form for 
use in connection with the medical examination 
was devised, a complex coordinator was de- 
veloped and tested in relation to success in 
flight training, and criticisms of certain visual 
tests were voiced. Flight surgeons rather than 
professional psychologists were chiefly respon- 
sible for the first three developments, while a 
psychologist, as well as medical men, had a 
hand in the last mentioned development.” 
Reviewing the early work in aviation psy- 
chology we see that the ground had been 
broken and problems had been clarified. How- 
ever, these earlier beginnings have been criti- 
cized for (1) their emphasis on selection to the 
exclusion of the learning process and other 
functions affecting flight performance; (2) their 
neglect of job analysis as a means of determin- 
ing the exact value of the task performance by 
pilots; (3> their failure to conduct research 
in the air; and (4) their failure to develop 
trustworthy methods for rating or measuring 
flight performance so that the value of tests 
in selecting aviators could be determined. 
Where tests had been used there had been too 
much dependence upon their “reasonableness,” 
upon what is sometimes called face validity, 
and there had been a parallel failure to de- 
termine experimentally the actual value of these 
tests in selecting flyers. 
To quote further: 
“By 1941, when the United States entered 
World War II, a well-organized program of 
aeronautics research was under way, and there 
* Prepared by Cdr. Alan D. Grinsted, MSC, USN. 
125 AVIATION MEDICINE PRACTICE 
were at least 100 psychologists who had ob- 
tained direct experience in such research. This 
development was largely traceable to the sup- 
port given since 1939 to psychological research 
in aviation by a Federal agency, the Civil Aero- 
nautics Authority (now called the Civil Aero- 
nautics Administration). 
“In the fall of 1939 this authority embarked 
on a program of training 10,000 civilian pilots, 
chiefly among the undergraduate personnel of 
American colleges and universities, as part of 
a wide-scale effort to develop the light plane 
industry by encouraging private flying. Through 
the efforts of its director of Research, Dean 
R. Brimhall, a fund was set aside for psycho- 
logical research in the selection and training 
of civilian aircraft pilots. This fund, increased 
as the civilian pilot training program expanded, 
was allocated to the National Research Council, 
which established a Committee on Selection and 
Training of Aircraft Pilots to plan and super- 
vise research. Included in this was an executive 
subcommittee of psychologists and representa- 
tives from aviation medicine, civilian flying as- 
sociations, air arms of the services, and com- 
mercial air lines. , . . 
“The research program of this committee 
naturally included the selection and classifica- 
tion of pilots. However, from the beginning, 
the importance of training problems was rec- 
ognized, and attention directed at once towards 
the investigation of the learning processes and 
of other factors involved in the acquisition of 
pilot skill. Rating scale technique and litho- 
graphic and photographic methods of recording 
were developed, the aim being to procure reli- 
able measures of pilot performance during 
flight. Problems of tension and fatigue, the ef- 
fects and treatment of motion sicknesses, and 
similar maintenance problems were likewise 
investigated. Moreover, these problems were 
studied, not alone in the laboratory, but in the 
cockpit of the plane under actual flight condi- 
tions. . . . Such investigations produced signifi- 
cant findings which were employed in connec- 
tion with the military effort during World 
War II.” 
The program thus described represented the 
first really comprehensive and systematic ap- 
proach in this country to problems of aviation 
psychology. Not only was the scope broadened 
to embrace the training and maintenance of 
flyers as well as their selection; the program 
also stressed for the first time the need for 
reliable measures of flight performance, investi- 
gations under actual flight conditions, and ex- 
periments to determine the validity of tests 
of flight performance. There was an attempt 
to overcome these faults in the program 
launched in 1939, conducted by cooperating 
psychologists under the general direction of 
the Committee on Selection and Training of 
Aircraft Pilots. 
To a large extent Navy aviation psychology 
originated in work sponsored by this committee 
as a part of this program. Many of the civilian 
investigators eventually accepted naval com- 
missions, and the work expanded as the pres- 
sure of the war emergency increased. However, 
naval psychology, as related to medicine, was 
not limited to activities concerning aviation, as 
is apparent when Jenkins states as follows: 
“More than 200 psychologists were commis- 
sioned under the auspices of the Bureau of 
Medicine and Surgery, divided approximately 
equally between programs in neuro-psychiatry 
and aviation psychology. . . . The program of 
commissioning psychologists was begun in the 
Navy as early as July of 1940, followed by calls 
to active duty in that same year.” 
At first a few psychologists had been pro- 
cured for assignment to training facilities under 
the conviction that they could be of help in 
giving tests “and in other ways.” The test 
program had been developed; the “other ways” 
represented the conviction that psychologists, 
since they dealt with human nature, must be 
able to do something besides administer tests. 
As indicated in the quotation above, they were 
used in two major programs and found im- 
portant roles in both. We are here concerned 
primarily with psychology in aviation medicine, 
and no attempt will be made to review the work 
of those in the neuropsychiatric program. 
Nevertheless, the clinical aspects of the psy- 
chologists’ contribution cannot be entirely 
ignored, for the aviation psychologist spent 
much of his time as a counselor to the student 
aviators, and his work in many ways supple- 
mented that of the flight surgeon. In fact, in 
many activities shortage of medical personnel 
made it necessary that the services of the stu- 
126 Chapter 7.—AVIATION PSYCHOLOGY 
dent advisory officer, as the psychologist was 
often called, be utilized in functions that would 
otherwise have fallen to a neuropsychiatrist. 
Consequently, the psychologists who were first 
procured with the vaguely formulated idea that 
they could help with selection “and other 
things” had, by the end of the war, been as- 
signed a fairly definite role in the program for 
training flight personnel, which role included 
some clinical counseling of individuals in addi- 
tion to duties more specifically related to train- 
ing problems and research. 
In order to understand the role that the psy- 
chologist has played in aviation medicine, it is 
probably necessary to consider, at least briefly, 
the background of psychology as a science, and 
some of the problems it has had to face. In 
the first place it is young as sciences go. Eighty 
years ago there was as yet no such thing as 
a psychology laboratory. Psychology was, in 
both the academic and popular sense, a fit sub- 
ject for armchair dreaming. Even today there 
are still some small colleges who teach some- 
thing they call psychology in their philosophy 
departments. Psychology has only just suc- 
ceeded in finding recognition as a science. 
Then, in the second place, psychology has 
suffered from a certain unwanted popularity. 
Simply because it concerns itself with prob- 
lems of human nature, everyone who has ever 
felt curious about his fellow humans feels justi- 
fied in thinking of himself as a pschologist of 
a sort. Furthermore, this natural interest has 
been exploited by popular writers, fortunetel- 
lers, mind readers, and many others who have 
found profit is claiming a right to the title 
“psychologist.” The loose use of the words 
“psychology” and “psychologist” has done much 
to confuse the average person regarding their 
true meaning. 
The consequence of these problems has been 
that the scientific psychologist has been rather 
more inclined than he might otherwise have 
been to put heavy emphasis upon strict adher- 
ence to the scientific method. In addition, the 
very nature of his subject matter has been 
such as to cause him to analyze himself and 
his own methods. Knowing something of the 
frailties of human beings he has tended to 
be unusually skeptical of those who make gen- 
eralizations about human data, even to the 
point of being skeptical about himself, his own 
observations, and his own results. He knows 
that no one individual can ever expect others 
to interpret the universe just as he does. He 
also knows that he can never assume that his 
interpretation is any more certain to be cor- 
rect than that of another person unless he 
makes use of many and crucial checks on what 
he perceives. In order to avoid giving cause 
to any who might confuse him with the arm- 
chair theorist or the fortunetellers and others 
who make false claims to an understanding of 
their fellow humans, the scientific psychologist 
has disciplined himself rigorously in adherence 
to scientific procedure and has forged ahead in 
the shaping of tools and techniques for the ac- 
curate measurement and controlled manipula- 
tion of data concerning problems of human be- 
havior. 
Thus it is that in the relatively new and fast- 
growing field of aviation medicine psychologists 
have found a welcome. The clinically-trained 
man of medicine found his interest in and 
knowledge of human problems neatly supple- 
mented by the trained psychologist’s interest 
in and technique for inquiring into some of 
those problems. Psychologists who at first were 
procured to help administer tests and “other 
things” found themselves, by the end of World 
War II, working with problems in many fields. 
Their acceptance into the naval aviation medi- 
cine family was finally signalized by the crea- 
tion of regular Navy billets for psychologists 
in 1947, and training in the scientific applica- 
tion of psychological techniques has become a 
regular part of the training of the naval flight 
surgeon. 
WHAT IS SCIENTIFIC PSYCHOLOGY? 
The movies and radio have created in the 
popular mind the idea that all a person needs 
to do to be a scientist is to don a white coat 
and stand behind a table covered with test 
tubes and beakers. Few people seem to take 
the time to try to analyze the meaning of the 
word science which is so commonly used and 
so often misused. 
What is science? Is it a white coat? A set 
of instruments? A body of knowledge? Science 
is much more than these. It is, first and fore- 
127 AVIATION MEDICINE PRACTICE 
most, a way of searching for the truth. It is a 
method, a type of approach to problems, and it 
is fundamentally the same whether used by 
the butcher, the baker, the candlestick maker, 
the physicist, the physiologist, or the psycholo- 
gist. It is a method of investigation, and he 
who uses that method is a scientist. 
Science involves, first of all, the objective 
attitude. This attitude is that of the open mind. 
The scientist must train himself to view his 
data without bias or preconceived notions, and 
to concern himself more with the exactness of 
data and the validity of his conclusions than 
with any possible personal value so far as he is 
concerned. For the true scientist must be im- 
personal and skeptical, even toward himself. 
The non-scientific observer often finds this a 
very hard attitude to maintain. When one is 
dealing with persons, it is difficult to be im- 
personal. And when you are one of those per- 
sons the difficulty is multiplied. The easy way 
is always to accept the traditional or popular 
notions. “Common sense” so often furnishes a 
“reasonable” answer! And yet “common sense” 
has led to many false answers and has long 
lulled mankind into complacent acceptance of 
ignorance that might easily have been dis- 
pelled by a little skepticism leading to experi- 
mentation. Folks might still be blaming malaria 
on the dampness of the night air if it weren’t 
for a little healthy skepticism. 
Yes, the scientist must dare to doubt the 
ready answers of tradition and ancient author- 
ity. He must have uppermost in his mind the 
questions, “What is the evidence? How do I 
know this to be true?” 
In addition, he must also ask himself these 
questions about his own conclusions. He must 
be able to recognize valid evidence when he 
meets it and know how to remove the disguise 
from the phoney “facts” that sometimes slip by 
with the appearance of truth. In order to do 
this he cannot always trust his own observa- 
tions. He knows that two people seeing the 
same thing often report quite differently on 
what they see. So, he doubts his own observa- 
tions. That means that he is forced to resort 
to various techniques that will make it possible 
for others to check his results. He must ob- 
jectify his data and, if possible, gather his in- 
formation in such concrete form that no one 
can say, “That’s just what you think.” 
Of course, objectivity is relative. A certain 
amount of subjective judgment is inevitable, if 
only in the interpretation of our objectively 
gathered data. In some psychological or physio- 
logical experimentation the subjective judg- 
ments play such an important role that it is 
necessary that the scientist compare many ob- 
servations. His own observations will vary 
with themselves, observations between observ- 
ers will vary, and variation will occur even in 
the conditions observed. The only answer is 
found in numerous observations systematically 
controlled. 
Finally, the scientist must adhere to certain 
rules of the game. One of the rules is that he 
must be logical. Perhaps he need not have 
studied formal courses in logic, but if he as- 
sumes that all redheads make good pilots be- 
cause he once knew a redhead who was a high- 
flyer, he is not likely to contribute much to the 
world of science. To be a scientist, a man must 
think clearly, state his problems in a meaning- 
ful way, and then follow the so-called scientific 
method. This procedure has four steps: First, 
there is the accumulation of existing data or 
evidence; second comes the classification of this 
evidence in orderly fashion; third, the scientist 
draws a generalization (and this is where the 
ancient philosopher used to stop, thinking that 
he had arrived at the truth; modern loose 
thinkers like to stop here, too—it often saves 
them from changing their opinions) ; and 
fourth, the scientist, recognizing his generaliza- 
tion as being only a hypothesis (a good guess), 
proceeds to put it to every conceivable test to 
discover its truth or determine its limitations. 
This last step is crucial. Without it there is no 
true science. 
The way in which a scientist tests his hypo- 
theses varies with the circumstances. The ideal 
method is the experiment in which quantitative 
measurements are obtained under conditions so 
carefully controlled that a repetition of the ex- 
periment in the same manner by another scien- 
tist can be expected to yield the same data. 
Scientific method in aviation psychology is 
in no sense different from scientific method ap- 
plied to aviation medicine as a whole. Actual 
experimentation is the ideal method of verify- 
ing our hypotheses, but is not always practi- 
128 Chapter 7. —AVIATION PSYCHOLOGY 
cable when dealing with human beings. Much 
successful experimentation has been done, es- 
pecially in the sensory fields as they are affected 
by conditions of flight. Problems surrounding 
the states known to aviators as vertigo furnish 
a neat illustration of the kind of psychological 
experimentation that has been profitably car- 
ried on in the past and that is continuing. As a 
result of the strict application of scientifically 
controlled procedures, more and more light is 
being thrown into this no man’s land of fears 
surrounding disorientation, autokinesis, and 
kindred perceptual confusions attendant upon 
the pilot “lost” in space. 
The primary difficulty in any scientific ap- 
proach to psychological problems has always 
been to find means of obtaining accurate meas- 
urement of the variables under consideration. 
How dizzy is a pilot after two slow rolls? As 
dizzy as the blonde next door? How can you 
tell? Or, how hot is a “hot pilot”? Can you 
figure a way to measure this kind of heat? 
Well, there are plenty of measurements that 
we would like to get that are so far inacces- 
sible. Nevertheless, much headway has been 
made in the measurement of many character- 
istics of the human individual who was con- 
sidered a few decades ago to be beyond the 
reach of any scientific yardstick. Navy psy- 
chologists have not yet figured out how to meas- 
ure accurately the feelings of a man who falls 
from a plane without a parachute, but by use 
of tests, that have been developed, they can 
name the odds on a man’s chances of passing 
flight training. 
INDIVIDUAL DIFFERENCES 
If the Navy receives delivery of a thousand 
new airplanes of a certain type we may be rea- 
sonably sure that they will be uniform in con- 
struction and ability to perform. But to find 
the pilots who are able to fly these planes with 
satisfactory and uniform degrees of skill pre- 
sents a major problem. That identical machines 
vary in production when under different opera- 
tors has long been recognized in industry. Folks 
differ by nature as well as training, and of two 
workers on the same job, one may be found two 
or three times as efficient and productive as the 
other. A job that is boring to one worker may 
prove satisfactory to another and too difficult 
for a third. Consequently, the industrial world 
is placing increasing emphasis on the placement 
of each individual on a job for which he is 
suited, both in ability and temperament. The 
Navy, likewise, has learned that many of the 
problems of aviation depend upon selection of 
the right man for the job, and probably no- 
where has recognition of individual differences 
paid higher dividends. 
The whole idea of scientific selection is 
based on the fact that no matter what charac- 
teristic of mankind we measure, the measure- 
ment obtained will be found to be distributed 
in the population according to a certain pat- 
tern. It doesn’t matter whether we measure 
physical traits like height or thickness of toe- 
nails, mental characteristics like intelligence or 
ability to memorize telephone numbers, person- 
ality traits, emotional stability or what have 
you; the resulting measurements are always 
found to be distributed in the population in the 
same general way. 
Suppose we have measured the heights of 
a large group of men. Now let us arrange the 
men in lines, standing all those of the same 
height in the same line. With these lines ar- 
ranged in order of height, the short men on the 
left and the tall men on the right, the columns 
would form an arrangement somewhat like 
Figure 7-1. 
If some measurement other than height had 
been obtained, the individuals would not fall 
in the same columns, but the pattern of the lines 
would be similar. As indicated, half the group 
falls in the middle range. These are the average 
or near-average individuals in regard to the 
trait measured. Measurements above and be- 
low this middle range are fewer and fewer, so 
that the lines become shorter and shorter as 
we move away from the average in either di- 
rection. 
We can picture the same thing by drawing 
a smooth curved line, such as would include 
the contour of the figure above. In such a graph 
the height of the curve at any point would 
represent the number of times the various 
measurements plotted on a baseline were found 
to occur in the group measured. This is an 
example of the normal probability curve for 
129 AVIATION MEDICINE PRACTICE 
Figure 7-7. 
individual differences. It is characterized by 
its bell shape, and is symmetrical about its 
center, which is the average or mean. 
Such a distribution curve is of value in many 
ways. Most important perhaps, is the fact that 
it enables us to judge the importance of a 
measurement or score in relation to other meas- 
urements or scores. For example, if we find 
that a certain man in a gun factory can turn 
out 100 parts per hour, the information is 
relatively meaningless until we find that this 
is better than 9 out of 10 men do, which fact 
indicates his superiority. 
Let us suppose that you need a crew of men 
to copy long lists of names and you have 100 
men to choose from. In order to get those who 
can do the job the fastest, you have each write 
Wadek Gyzinski and time him as he writes. 
When you have timed all 100 men, you may well 
find yourself with a very confusing accumula- 
tion of figures. 
In order to analyze such numerical data 
adequately, you will do well to systematize it in 
the form of a frequency distribution. With all 
of your time records converted to the nearest 
number of whole seconds, you might get some- 
thing like Figure 7-1. 
Score 
(Number of sec- 
onds required to 
write Wadek Gy- 
zinski) 
Tallies 
(Each tally represents one 
man who took the cor- 
responding number of sec- 
onds to write Wadek Gy- 
zinski) 
Frequency 
(The number of 
men who took 
the correspond- 
ing number of 
seconds to write 
Wadek Gyzinski) 
3 
1 
1 
4 
mi 
4 
5 
im 
im 
im jm mi 
24 
6 
M 
mi 
im im im im im i 
36 
7 
im 
im 
am im mf in 
28 
8 
im 
i 
6 
9 
i 
1 
N = 100 
130 Chapter 7. —AVIATION PSYCHOLOGY 
Such a frequency distribution makes it easy 
to draw a graph of the results, with the scores 
arranged along the horizontal axis (abscissa) 
button is usually treated as normal in making 
computations, however, unless the skewness is 
extreme. Such extremely skewed distributions 
have a noticeable “tail” when pictured in a 
graph. This is because of a few atypically 
high or low scores. If unusually low scores oc- 
cur at the left, the distribution is negatively 
skewed; if at the right the distribution is posi- 
tively skewed. Our distribution above is not 
noticeably skewed. 
Now suppose it is desirable to represent the 
above data in a sort of simple shorthand. Then 
a measure of central tendency will give the 
typical performance of the group. The meas- 
ure of central tendency most often used is 
the arithmetic mean or common average. It is 
obtained by adding all the scores in the series 
and dividing by the number of scores. Thus, if 
we add all the scores made by the men writing 
Wadek Gyzinski, we find that it took the 100 
men a total of 608 seconds, which gives us an 
arithmetic mean of 6.08 sec. In common par- 
lance, it took the average man 6.08 seconds 
to write Wadek Gyzinski, This method of com- 
puting the mean can be used satisfactorily when 
there are only a few scores. However, a shorter 
method is available for computing the mean 
from large numbers of data grouped into fre- 
quency tables. 
Another measure of central tendency is the 
median. When the measurements are arranged 
in order of size, the median is the point that 
divides the series of scores into two equal 
groups. It may be the middlemost case or it 
may be a score that lies half way between the 
two middlemost scores. The median of our 
distribution would be 6.58 seconds, which can 
also be computed from the frequency distribu- 
tion. One other measure of central tendency 
occasionally used is the score occurring most 
frequently, and this is called the mode of the 
distribution. The mode of our distribution is 
six seconds. Distribution may also be bimodal, 
with two points of high frequency; or mul- 
timodal, with many such points. 
Each of these measures of central tendency 
has its place. Wherever accuracy is important, 
and if it is not misleading, the mean should 
be used. Extreme scores, however, may be such 
as to render the mean a poor measure of cen- 
tral tendency. For example, if in our illustra- 
Figure 7-2. 
and the frequency with which each score oc- 
curs indicated on the vertical axis (ordinate). 
In this case there are 100 subjects, so that the 
vertical axis gives us both the number and 
percentage of men for each score. A graph 
in terms of percentage is often useful. 
If we had a large number of cases, our fre- 
quency polygon might be expected to approach 
the shape of a normal probability curve. Such 
curves are determined by so many factors that 
they are sometimes called curves of chance. In- 
deed, even the number of heads turned up when 
10 coins are tossed many thousands of times 
will arrange themselves in approximate ac- 
cordance with the normal probability curve or 
curve of chance. Of course, the perfect sym- 
metry of the normal probability curve is never 
actually attained, although there may be a close 
approximation to it. Sometimes, on the other 
hand, the distribution is skewed; that is, the 
scores are more numerous above than below 
the peak of the curve or vice versa. The distri- 
131 AVIATION MEDICINE PRACTICE 
tion mentioned above, one man with an emo- 
tional disturbance kept trying for three hours 
before he succeeded in writing Wadek Gyzinski, 
inclusion of his time in our calculations would 
give us a mean of nearly 8 seconds, a grossly 
misrepresentative figure. On the other hand, 
the median would not have been greatly affected 
by such an extreme case. The median is usually 
more representative than the mean when there 
are few scores in the distribution, and particu- 
larly when atypical measures are included. It 
also has the advantage that it is easily com- 
puted. The mode also can be arrived at easily 
by inspection of the frequency distribution or 
a graph, but it is a crude measure, useful as a 
rule only for making a quick appraisal of the 
central tendency of the distribution. 
Unfortunately, it is often not enough that we 
know the central tendency of a distribution. 
Two distributions may have exactly the same 
mean and yet be very different. A much clearer 
picture of a distribution is obtained when the 
average is stated along with some measure of 
dispersion or scatter of the measures about 
that average. For example, in our illustration 
above, if we know only that the average man 
took 6.08 seconds to write Wadek Gyzinski, 
we do not know whether all 100 men took the 
same length of time or to what extent some 
were faster than others. 
The most easily understood measure of such 
variability is the range of distribution, which 
is simply the distance between the highest and 
lowest score (six seconds in our illustration). 
Where statistical detail is desired, however, the 
range tells too little about the pattern of the 
distributed scores. 
Another and infrequently used measure of 
variability is the mean deviation or average 
deviation which is obtained by calculating the 
amount by which each score deviates from the 
mean, then adding all the deviations, and find- 
ing their average. There are mathematical ob- 
jections to the use of this measure. 
The standard deviation is the most commonly 
used and most accurate. It is obtained by find- 
ing the square root of the mean of the squared 
deviations taken from the arithmetic mean of 
the distribution. In large distributions the nec- 
essary processes involved here would be long 
and tedious. However, simpler, short-cut meth- 
ods have been evolved for arriving at the same 
answer. (The probable error is a similar meas- 
ure being used less and less). 
The standard deviation (SD) or o tells us to 
what extent the scores in a distribution deviate 
from the mean; or to put it another way, it 
shows how near the mean is to being typical 
of all the scores. The smaller the S.D., the 
more typical is the mean, because the size of 
the S. D. is reduced as the scores cluster closer, 
and it becomes larger as the scatter of the 
scores increases. 
The S. D. also serves another useful purpose; 
it furnishes us with a means of stating the posi- 
tion of any given measurement or score in re- 
lation to its fellows. With a knowledge of the 
mean, we can say that such and such a score 
is above average or is below average. But, 
how much? A knowledge of nothing but the 
mean will enable us to tell almost nothing about 
the extent of deviation of any particular score. 
The standard deviation furnishes us with a 
scale for measuring such deviation through the 
calculation of what are known as standard 
scores (also called z-scores). The standard 
score is simply a statement of the deviation of 
a given score from the mean of the distribution 
expressed in S. D. units. If, for example, a 
score of 165 occurs in a distribution with a 
mean of 150 and a standard deviation of 30, 
this score may be said to fall 0.5 units above 
the mean. This (0.5) is, then, the standard 
score equivalent for the “raw” score of 165, 
and is calculated simply by subtracting alge- 
braically the mean from the raw score and di- 
viding by the standard deviation. If the raw 
score is below the mean, this is indicated by the 
use of a minus sign. 
The use of the z-score enables us not only 
to state more clearly the position of any score 
within a distribution, but also makes it pos- 
sible for us to compare a man’s standing in 
various measures and equitably combine sepa- 
rate measures into a composite score, which 
combination would have been statistically un- 
desirable, using raw scores alone. The z-score 
also makes it possible for us to make a more 
nearly accurate comparison between the per- 
formances of two men where the tests for the 
two men are similar but not the same. This 
latter use is sometimes practically necessary al- 
132 Chapter 7.—AVIATION PSYCHOLOGY 
though inadvisable, and can be employed only 
where the tests have given to comparable popu- 
lations. For example, we may wish to know 
which of two men is the faster on a job of as- 
sembling small gun parts, but while they do 
similar assembly work, they work in different 
departments and the jobs they do are not 
identical. In such a case, we may know that 
Jones produces 57 units per hour on his job and 
Smith produces 79 units per hour on a slightly 
different type of assembly job. Since the jobs 
are not just the same, we cannot assume that 
Smith is the faster worker. Here, then, z-scores 
may prove helpful. If we know the average rate 
of production on both jobs and the standard 
deviations, we can calculate the z-scores, and 
we may find that Smith’s standard score is only 
1.2, whereas Jone’s score is 2.0, indicating that 
in comparison to others doing similar work, 
Jones is the faster The z-score, therefore, has 
many important uses. 
It is impossible here to go into great detail 
concerning statistical procedure in use in avia- 
tion psychology today, but some understanding 
of the concepts employed may be gathered from 
the discussion presented here. 
SELECTION* 
Two men want to enlist in the Navy. They 
are both healthy looking 18-year-olds, both 
enthusiastic about leading the Navy life. They 
both have good ears, good eyes, good teeth, and 
good hearts. But when they take one of the 
Navy’s paper-and-pencil tests, one passes, one 
fails. The one who fails is turned down. He 
cannot get into the Navy because he cannot 
answer a few questions on a sheet of paper. 
Twenty-five years ago this sort of procedure 
would have seemed the height of foolishness to 
many seasoned fighting men. Even today there 
are people to whom paper and pencil tests con- 
stitute adequate cause for a raise in blood 
pressure. But such tests are now standard 
Navy procedure and will likely remain so. Psy- 
chological tests have proved their usefulness. 
The fact that a man fails to make certain marks 
at the right time at the right place on the 
right sheet of paper means that he will not be 
accepted for general Navy training. 
What sort of justification is there for such a 
procedure? How does it make sense that we 
turn down a likely looking future navigator or 
gunner or radioman or aviator because he can’t 
answer a few questions? 
We have seen how men differ. Even if all 
men were born equal, they would get over it 
almost immediately. Every man differs from 
every other man. Every man has his own pat- 
tern of abilities, aptitudes and traits. That 
basic fact is fifty percent of the justification for 
selection. 
The other half of the justification is found 
in the differences among jobs. Jobs differ 
among themselves probably just as much as do 
individuals. Each job demands its particular 
sort of muscular movements, its particular sort 
of sensory keenness, of perception, of coordina- 
tion, of endurance, of intelligence. 
Modern industry and modern warfare are 
highly specialized activities. Neither in the 
armed forces nor in civilian production can we 
gain personnel efficiency without doing a decent 
job of finding specialized men to do these spec- 
ialized jobs. Perhaps any man can be taught to 
operate sonar, to make precise judgments about 
the time, pitch and loudness of sounds, to tell 
the differences between neutral flounders and 
enemy cruisers. But when one man is gifted 
with unusual ears, and this job can use unusual 
ears, it is wasteful not to get the job and the 
ears together. The man with the high quality 
ears will be likely to learn sonar skills sooner, 
likely to out-perform the man who lacks the 
basic auditory abilities. 
Once you have decided on selection, your 
selection pays off in proportion to your choosi- 
ness. If you have a large number of applicants 
and a selection procedure that is known to 
measure their potential usefulness for the job, 
the way to get the best performance, obviously 
enough, is to select only the very best men. The 
AAF conducted an unusual experiment during 
the war to show just how this economic factor 
works.** 
The AAF had a systematic and extensive 
program for selecting pilots. Before a man was 
* This section has been condensed and adapted from Naval 
Leadership, Book II: Psychology for Naval Leaders, Ch. VI, U.S. 
Government Printing Office, Washington, 1948. 
** From a report entitled Stanines, selection and classification for 
air crew duty prepared by: The Aviation Psychology Program, 
Office of the Air Surgeon, Headquarters, Army Air Forces. 
133 AVIATION MEDICINE PRACTICE 
accepted for training he had to pass medical, 
psychiatric, and psychological examinations. To 
check on the economy and effectiveness of this 
program after it had been set up, the AAF 
people let one thousand unscreened youngsters 
into their training program. This group had 
to meet the minimal medical requirements, but 
otherwise the group was composed merely of 
a thousand young men who wanted to fly. These 
aspirants were mixed in with the normal AAF 
trainees and given the same course of prepara- 
tion for flying. Careful records were kept, and 
this group was compared with groups that had 
been given the works — medical, psychiatric, 
and psychological examinations — and who had 
been allowed to go on to flight training only 
if they met certain standards. 
A good number of the unselected men suc- 
ceeded in winning their wings. But their train- 
ing was expensive business. The results showed 
that for each hundred of them who got through 
training, 297 of them fell by the wayside. 
So, to end up with 100 pilots, 397 men had 
to be entered into training. These men dropped 
out at various stages. Let’s say the average 
washout was dropped halfway through his 
training, and let us suppose that it costs $25,- 
000 to train a pilot. On the basis of these 
assumptions, the cost of producing 100 pilots 
from this unselected group would be $6,202,- 
500. Each pilot from this group would cost, 
then, $62,125. 
A second group was admitted to flight train- 
ing on the basis of (1) passing a psychiatric 
check, (2) making slightly below average 
scores on the AAF qualifying exam, and (3) 
making average scores on the AAF battery of 
aviation-selection tests. The results for this 
group show that for every 100 successes there 
were only 102 failures. To get 100 pilots, 202 
men must be started in training. Using the 
above assumptions about cost, the total ex- 
penditure for 100 pilots in this group was $3,- 
775,000, This gives a figure of $37,750 per 
pilot. 
A third group was more highly selected. 
They (a) passed the psychiatric exam, (b) 
obtained a slightly below average score on the 
AAF qualifying exam, and (c) obtained better• 
than average scores on the pilot-selection ex- 
amination. The results on such a group show 
that for each hundred men getting their wings 
only 56 wash out. This means that the training 
of a hundred pilots costs $3,200,000. or $32,000 
a pilot. This represents a hypothetical saving, 
as compared with the first groups, of $3,012,500 
per hundred pilots, or $30,125 per pilot. When 
you multiply the latter figure by the number 
of pilots in the AAF during the war, the total 
is something quite impressive even in an age 
when a billion dollars does not particularly im- 
press the taxpayer. 
MEASURING MAN'S ABILITIES 
There have been many techniques for “know- 
ing” men. Obviously enough, one good way to 
see whether a man can do a job is to watch 
him do it for a few years. His performance 
will give the best evidence as to what his even- 
tual performance will be like. But this proce- 
dure of getting a sample of work has serious 
drawbacks. In the first place it takes time. In 
the second place, it is often dangerous and ex- 
pensive to let an inexperienced man try his 
hand at running an intricate machine — like 
a $100,000 airplane or a 16-inch gun. In the 
third place, the sample of work tells only about 
present performance. It does not give clear 
information about how good the man will 
be after a period of training. 
We need a procedure that (a) does not take 
much time, (b) that is not expensive or danger- 
ous, and (c) that enables us to predict future 
performance. 
Aptitude tests, now available in many forms 
and for many purposes, meet all three criteria 
for a good selection procedure. They do not 
take much time. They are not dangerous (ex- 
cept when badly administered or interpreted). 
They are economical. And, when properly used, 
they allow a prediction about what we are most 
interested in — the future. 
At the beginning of World War II a group 
of psychologists undertook the job of building 
tests that would select naval aviators. The first 
step these men took was that of learning at 
first hand what a naval aviator had to do. They 
investigated the cadet’s ground school courses, 
poked into the things the aviator needs to know 
about navigation, communication, aerology and 
engineering. They studied the flyer’s move- 
134 Chapter 7. — AVIATION PSYCHOLOGY 
ments while in a plane, observing the number 
and variety of his coordinations, the number 
and variety of things he has to attend to, and 
how rapidly he must learn new ideas and new 
skills. 
All this intimate knowledge of the job served 
to give the psychologists hunches about what 
sort of measurable abilities and interests might 
differentiate — in advance — between the suc- 
cessful and the unsuccessful flight trainees. 
When hundreds of such hunches are combined 
with information gathered in previous research 
and are combined with the ideas of experienced 
pilots, the basic raw material of the test is at 
hand. 
Suppose our hunches led us to think that the 
following two questions would help in selecting 
men for aviation training: 
1. Which one of the following planes has 
two motors? 
a. The spitfire. 
b. The Hurricane. 
c. The Lightning. 
d. The Typhoon. 
e. The Kittyhawk. 
2. The speed of outboard motors is often 
controlled by: 
a. Changing the pitch of the propeller 
blades. 
b. Advancing or retarding the spark. 
c. Changing the angle of the propeller 
on the stern post. 
d. Raising or lowering the propeller. 
e. Loosening or tightening a brake on the 
flywheel. 
The correct answer to the first question is 
“c.” The correct answer for the second is “b.” 
Our problem now is to see, by actual experi- 
mental trial, whether these and hundreds of 
similar questions are answered any more cor- 
rectly by successful then by unsuccessful avia- 
tors. So we give our hundreds of questions to 
a thousand applicants for flight training. We 
record their answers and file the papers away 
for a few months. When flight training is com- 
plete, let’s say that five hundred of our cadets 
had won their wings and five hundred had 
washed out into gunnery school at Great Lakes. 
We now have a way to see which of our ques- 
tions have something to do with aptitude for 
flying. If the successful flyers answer a ques- 
tion one way and the washouts answer it an- 
other, the question is clearly related in some 
way to a man’s chances of winning his wings. 
Take question No. 1, above. Let us say that 
of the 500 who passed flight training, 320 an- 
swered the question correctly, and of the 500 
who failed, only 102 knew the right answer. 
The question looks like a good one to include 
in the test. If you bet that a man who knows 
the answer will get his wings, it looks like you 
have 320 chances out of 500 of winning. The 
man who does not know the answer is a longer 
shot. He has, if the odds hold up, only 102 
chances out of 500 of winning his wings. 
Not all questions, based on hunches, turn out 
so fortunately. Let’s suppose that of our 500 
who passed flight training 420 got the question 
right, and that of the 500 that failed, 415 knew 
the answer to the question. The question ob- 
viously does not do much to distinguish between 
passers and failers. We forget that question. 
It will do us no good at all. 
Just as with specific questions, the whole test 
must be put through its paces before we know 
how much good it will do us. Do people who 
make high scores in the test perform better on 
the job than do people who make low scores? 
Suppose we were required to find tests that 
would pick good machinists, that would tell us in 
advance the chances that any given man will do 
well in the machinists’ training and at machin- 
ists’ work. We may have to create our own test or 
tests for this job of selection. We would save 
a good deal of time, however, if we could use 
tests already constructed. The procedure would 
be to select available tests which seem likely 
to have something to do with being a good 
machinist. We may select a test of intelligence, 
a test of mechanical aptitude and a test of 
manual dexterity. Our hunches may say that 
these tests get at abilities the machinist needs. 
But before anyone can know whether these 
tests work, the tests must pass a test. Are 
scores on intelligence tests related to perfor- 
mance as a machinist? Does manual dexterity, 
as tested by our test, relate to the machinist’s 
performance? There is no way to answer these 
questions except to have a good look. We give 
our tests to a group of potential machinists, 
file the scores away, come back a year or so 
later, measure the machinists’ performance, 
135 AVIATION MEDICINE PRACTICE 
and compare the test scores with performance. 
If good performers got higher scores on any 
or all of our tests than did the poor performers, 
we have a potentially useful procedure for se- 
lecting machinists. 
VALIDITY 
When we talk about the relation between 
performance on a test and performance on a 
job, we are talking about the validity of the 
test. However good our items appear to be, 
however much sense the test or the battery of 
tests seem to make, we must always ask and 
answer the hardheaded questions, “Does the 
test do what it is supposed to do?” The validity 
of a test is a statement of the degree to which 
a test predicts (or measures) what it is sup- 
posed to predict or measure. 
The validity of a test (or battery of tests), 
the extent to which it does what it is supposed 
to do—is measured in terms of the relation 
between scores on the test and performance on 
the job. If all men who make high scores on 
a mechanical aptitude test have good records of 
performance as machinists, and low scores go 
with poor performance, the test obviously has, 
for the purpose of selecting machinists, good 
validity. If high scoring men and low scoring 
men do equally well on the job, the test has 
no validity and hence is useless for this sort of 
selection. 
It is important for many reasons to know 
precisely how valid a test is. It is necessary to 
determine the exact relation between scores on 
the test and actual performance on the job. 
This means we must not only score the test 
quantitatively, but we must find some way of 
measuring performance. The latter problem is 
often a difficult one. Human performance is 
hard to measure, particularly on intricate jobs. 
The problem of measuring performance is the 
problem you will hear test-constructing people 
refer to as the “problem of criteria.” There 
must be a criterion of performance before we 
can measure the relation between our tests and 
what our test tests. If we want to see whether 
or not we have picked good machinists or gun- 
ners, we must have a way of recognizing a good 
machinist or gunner when we see one. And it 
would be better if we could measure precisely 
how good. Often it is necessary to say a ma- 
chinist is good, if he received high grades dur- 
ing training or if his supervisors on the job 
rate him as good. Sometimes we have to say 
a man is good if he passes his training course. 
In selecting naval aviators, for example, the 
good men were defined as those who passed 
training, the bad as those who failed. The 
aviation selection tests were evaluated in terms 
of their ability to pick men who passed and to 
reject men who failed in flight training. These 
tests were validated against a pass-fail criter- 
ion. Whether the criterion is a matter of rat- 
ings by competent judges, of grades received in 
training, of precise measurement of perform- 
ance, or of over-all passing or failing in train- 
ing, there must be a sound criterion or we will 
never be able to tell whether the test is doing 
the job. 
The relation between test scores and the 
criterion is stated in terms of coefficients of cor- 
relation (or coefficients of validity, when re- 
ferring specifically to problems of validation). 
CORRELATION 
There are several sorts of coefficients of cor- 
relation. But the principle is essentially the 
same for them all and can be illustrated by the 
simple rank-order correlation coefficient. Sup- 
pose fifty people took a college entrance exam- 
ination. And suppose the college grades for 
these fifty were also available. To obtain a 
measure of the relation between the test and 
the performance you would first rank the in- 
dividuals from 1 to 50 on the basis of their 
test scores, with the highest scorer being given 
a rank of 1; the second highest, 2; the third 
highest, 3; and so on. Then you can compare 
the rank of each individual in one list with his 
rank in the other. Now, if it turns out that 
the man who scores first on the test also scores 
first in grades, that the man who scores second 
on the test scores second on grades, and so on 
throughout, a perfect correspondence of rank 
maintaining for each person, we get a perfect 
positive correlation. If we were sure that such 
a correlation were not accidental, we could then 
predict from the test exactly what a man’s 
grade standing would be. 
If there were a perfect reversal of ranks, 
with the first man on one being fiftieth on the 
136 Chapter 7.—AVIATION PSYCHOLOGY 
other, the second man on one being forty-ninth 
on the other and so on through the list, we 
would have a perfect negative correlation. A 
high score on the test would always mean a 
correspondingly low score in grades. The pre- 
diction would still be perfect but with a nega- 
tive sign. 
Such perfect correlations (expressed as co- 
efficients of plus 1.00 or minus 1.00) rarely 
happen. It is much more likely that the man 
who ranks first on the scholastic test would be 
near the top in academic grades, and that the 
man who scores at the bottom on the test 
would be near the bottom in grades. By some 
fairly simple computations, based on the differ- 
ences in rank for each individual, it is possible 
to reach a precise numerical description of the 
relatedness of the test scores and the grades. 
These coefficients of correlation are expressed 
in plus or minus decimals falling somewhere 
between plus 1.00 and minus 1.00. A coeffi- 
cient of .90 would indicate a high degree of 
relatedness, a good chance of predicting grades 
from test results. A coefficient of .60 would 
indicate a sizable relation, with definite but 
limited prediction, A coefficient around zero 
would mean that the test and grades have no 
relation and there is no way of predicting from 
the test what the man will do in the classroom. 
In actual experience with aptitude tests, a 
validity coefficient of .30 sometimes means the 
test can be useful. But the usefulness of the 
test increases as its validity goes up. A validity 
coefficient of .60 is considered good, one of .80 
or above is generally regarded as excellent. 
There are many tests now in use which are 
still essentially unvalidated. Some have been 
validated against doubtful criteria. Often it is 
possible to defend unsatisfactory validated tests 
on the grounds that they are at least better than 
unguided intuitions. But we can never be cer- 
tain a test will do its job unless we have 
precise figures concerning its validity. 
THE VARIETY OF TESTS 
In the last 25 years psychologists have con- 
structed a wide variety of tests for a wide 
variety of purposes. There are a large number 
of intelligence tests; there are mechanical, 
musical, clerical, scientific and scholastic apti- 
tude tests; there are dexterity tests and tests of 
motor function; there are personality tests and 
interest tests. When confronted with the as- 
signment of selecting men for a specific job, 
the psychologist can often use a group of tests 
already available. For any specific job, how- 
ever, he must know in advance the precise re- 
lation between scores on any test he uses and 
performance in the job he is interested in. 
He can gain this knowledge only through a 
thorough investigation of the validity of the 
test for his particular criterion. It is not pos- 
sible to know how any test or battery of tests 
will work in a particular job of selection until 
the tests are tried out specifically in that job. 
THE ACTUARIAL NATURE OF SELECTION TESTS 
We have seen that a psychometric selection 
program cannot function unless there are more 
applicants for jobs than there are jobs. Tests 
always select from among. We saw also that 
tests generally select some men who are poor, 
who will fail, and eliminate some who would 
do well at the job. This is just another way 
of saying that no test or battery of tests has 
perfect validity. But usable tests have known 
validity. That means that we know when we 
use a test what betting odds we are fooling 
with. We know, given the test’s coefficient of 
validity, that, say, of the thousand men who 
make this particular score, 840 will give satis- 
factory performance on the job. And we know 
that of the thousand that score below a certain 
minimum, only 220 will perform satisfactorily 
on the job. Given such information we would 
have no doubt about which thousand we would 
hire or accept for enlistment or send to a spe- 
cial school. But test results do not give us the 
basis for making precise prediction about the 
single individual. Psychometric methods are 
actuarial methods. 
The insurance company never knows when 
any given policy-holder will die and become 
a drain on the company treasury. But the in- 
surance company still makes money by know- 
ing pretty precisely the life expectancy of all 
men, say, 25 years of age. They can bet that 
a certain small percentage will die this year, a 
certain percentage 10 years from now, a cer- 
tain percentage 50 years from now. They hope 
137 AVIATION MEDICINE PRACTICE 
any new policy holder will live to grandfatherly 
health, but they cannot predict anything about 
him except his chances. He has so many chances 
in one hundred of living to be 80, Psychometric 
tests work the same way. The individual who 
scores at a certain level on a certain test has, 
as far as we can tell, seventy chances out of 
a hundred of succeeding at the job. He has 
thirty chances out of a hundred of failing. 
That is all the test can tell us. If we knew 
all about the man, we might be able to predict 
with complete certainty what he will do. But 
tests are not yet that good. 
The actuarial nature of tests means that the 
man who interprets tests must not be surprised 
if tests make errors. And the administrator 
should not bet on any individual beyond the 
limits of safety indicated by the test. No test 
wins all the time. But in the long run and with 
large numbers, tests with a satisfactory validity 
will pay off handsomely. 
NAVAL AVIATION CADET SELECTION TESTS 
There are now three tests in use for selecting 
cadets in naval aviation. These tests were intro- 
duced in the first place only after it had been 
demonstrated that they would consistently and 
reliably differentiate between those who ulti- 
mately passed and those who ultimately failed 
in naval aviation training. These tests now in 
use represent the most effective combination re- 
maining of more than forty that were tried 
out. Each test was given to a large number 
of applicants, the results not being used to 
select in this case. Then the scores were kept 
in “cold storage” until those tested had either 
passed or failed flight training. Then the tests 
were checked against actual performance in 
terms of pass-fail data, and were retained for 
further study only when they significantly dif- 
ferentiated passers from failers and did not 
duplicate other promising tests. The three 
tests now in use were finally retained after a 
series of cross-checks had eliminated all the 
rest. 
Such tests are of no value unless information 
concerning their content and the manner of 
scoring them are kept inviolate. Their value is 
also diminished when they are used in a manner 
that deviates from that employed during the 
original standardization process. For these rea- 
sons the responsibility for the custody of these 
tests and for their proper administration ac- 
cording to prescribed procedures rests in the 
hands of the flight surgeon or aviation medical 
examiner. 
These tests were standardized in terms of 
the relative percentages of men failing in flight 
training at each score level, and figure 7-3 shows 
how some of this original data for two of the 
tests shaped up. Since then, the Aviation Psy- 
chology Branch of BuMed has maintained con- 
tinuous surveys of the effectiveness of these 
tests, measured in these terms. 
THE FLIGHT APTITUDE RATING 
This is computed, according to a simple for- 
mula, from the combined scores on the three 
tests. The Flight Aptitude Rating (FAR) in- 
dicates the probability that a cadet having a 
given score-combination will ultimately pass 
the flight training course and be designated as 
naval aviator. These probabilities are stated in 
the following table, which is based upon long- 
term studies of large groups of entrants with 
an over-all attrition rate of about 30 percent: 
Percent Actually 
FAR Failing in Training 
A 0-6% 
A— 7-12% 
B 13-18% 
B— 19-24% 
C 25-31% 
C— 32-37% 
D 38-43% 
D— 44-49% 
E ,-.... 50% or more 
THE AVIATION CLASSIFICATION TEST 
This is essentially a test of general intelli- 
gence, worded to have a Navy flavor. Men who 
score low on this test tend to have serious diffi- 
culty in understanding complicated instructions 
or orders. The test is especially suited to the 
prediction of success in ground school. For ex- 
ample, in one group of 5,408 men who went 
through training in 1943-44, 5.6 percent failed 
in ground school. Most of these failures were 
men who had scored low in the Aviation Clas- 
sification Test, The following table shows the 
percentage of each letter-grade group which 
failed in ground school : 
138 Chapter 7. — AVIATION PSYCHOLOGY 
PERCENTAGE OF FAILURES FOR 
IB. L AND M.C.T. COMBINATIONS 
THIS CHART IS BASED ON 3294 CASES WHERE TESTS WERE NOT USED IN THE ORIGINAL SELECTION 
SHADING INDICATES THAT THE PERCENTAGE OF FAILURES IN THAT CELL IS NOT STATISTICALLY RELIABLE 
NOVEMBER I, 1942 D.W f - WA S 
Figure 7-3 
ACT Letter 
Percent Failing 
Grade 
In Ground School 
A 
0% 
B 
1% 
C 
5% 
D 
14% 
E 
21% 
THE MECHANICAL COMPREHENSION TEST 
This test (the MCT) deals with the ability 
to handle the familiar, simple mechanical con- 
cepts of everyday life. Scores on this test have 
been found consistently to bear a direct and 
positive relationship to ultimate success or 
failure in flight training. For example, a tabu- 
139 AVIATION MEDICINE PRACTICE 
lation involving the records of 7,685 cadets, 
shows that for each letter-grade, the following 
percentages failed in flight training for any 
and all reasons: 
terests. Research has determined that each 
scored answer bears a quantitative relationship 
to ultimate passing or failing in flight training. 
No single item is heavily weighted. Certain 
total patterns of response have, however, been 
found to be associated with high washout rates 
in training, while others normally accompany 
low washout rates. The following table, based 
upon the records of 7,744 men starting train- 
ing in 1943, shows the actual percentage fail- 
ing at each letter-grade: 
MCT Letter 
Perecentage Failing Flight 
Grade 
Training for any Reason 
A 
27% 
B 
36% 
C 
47% 
D 
62% 
E 
flight training) 
Percentage Failing 
BI Letter Grade 
in Training 
A 
29% 
B 
33% 
C 
41% 
D 
50% 
E 
58% 
The table shows that a man scoring D on the 
MCT was more than twice as likely to be 
dropped from the pilot training course as a 
man scoring A. Notice was taken of this fact, 
and directives were later issued to reject men 
who scored D as well as those who scored E. 
The above table gave figures on attrition in the 
pilot training course for all reasons, including 
flight failure, ground school failure, disciplin- 
ary action, or other causes. The selective value 
of the MCT becomes even more marked, how- 
ever, if consideration is given only to those 
men who were dropped for flight failure. This 
is shown in the following table: 
Test standards can be raised or lowered— 
with known effects—to comply with the supply- 
and-demand situation at any given time. When 
applicants are plentiful and billets are few, 
the passing score can be set high enough to 
admit only the very best risks. If it should 
ever become necessary to admit almost all the 
applicants, the passing score could be lowered 
to a point at which only the very worst risks 
would be eliminated. 
TEST SCORES AND PERFORMANCE IN COMBAT 
The tests were set up to accomplish one 
thing—to designate at the Selection Board 
those men most likely to wash out in training. 
The tables given show that the tests accom- 
plish this in reliable fashion. They make it 
possible for the Navy to train more men in 
less time than would be possible in dealing with 
unselected groups. Computations show that the 
savings run into millions of dollars and, pos- 
sibly more important in wartime, into many 
thousands of hours of training time. 
While this situation was favorable, it still 
left one major question unanswered. It was at 
least theoretically possible that, by selecting 
men who would do well in training, the Navy 
was tending to select docile, well-behaved men 
who would not be outstanding in combat. Put 
in other words, there was a theoretical possibil- 
ity that the tests, while positively related to 
performance in training, were more or less 
MCT Letter 
Percentage Dropped for 
Grade 
Flight Failure Only 
A 
7% 
B 
14% 
C 
19% 
D 
30% 
Thus, when flight failures only are consid- 
ered, a man who scores D on the MCT is more 
than four times as likely to wash out as a man 
who makes an A. 
THE BIOGRAPHICAL INVENTORY 
Flight surgeons have long sought to appraise 
a candidate’s personal history, interests, and 
attitudes in attempting to predict his probable 
performance as a pilot. The Biographical In- 
ventory, based upon statistical analyses of thou- 
sands of pilot records, does with mathematical 
precision what the flight surgeon sought to ac- 
complish on the basis of professional skill, ex- 
perience, and intuition. 
The Biographical Inventory is a non-time- 
limit questionnaire, containing questions on the 
applicant’s personal history, attitudes, and in- 
140 Chapter 7. — AVIATION PSYCHOLOGY 
negatively related to performance in combat. 
The answer could be obtained only by getting 
appraisals of combat performance on some hun- 
dreds or thousands of men for whom test-scores 
were available. 
In 1944, DCNO(Air), in collaboration with 
Chief BuMed, made it possible for the Aviation 
Psychology Branch to send specialists into the 
advanced areas to obtain individual combat ap- 
praisals. By the end of the war, approximately 
6,000 individual appraisals had been obtained 
from pilots in the war zones. While a detailed 
description of this work is not in order here, it 
may be said that a review of these records of- 
fers assurance that the use of the FAR in 
selecting pilots does not reject undue propor- 
tions of good combat men when it designates 
men who will do well in training. Indeed, 
while the difference does not meet conventional 
standards of statistical significance, there is a 
slight tendency for men rated as high in combat 
performance to make higher FAR’s than men 
rated low in combat. Furthermore, it has been 
established that the use of the tests, including 
possible rescoring of the BI, can be made to 
increase the proportion of good combat pilots 
and reduce the proportion of poor combat 
pilots. 
BIBLIOGRAPHY 
1. An Historical Introduction to Aviation Psychology. 
Prepared by National Research Council Committee 
on Selection and Training of Aircraft Pilots. Report 
No. 4. Washington, D. C. Division of Research, Civil 
Aeronautics Administration, 1942. 
2. Bingham, W. V. S., Aptitudes and Aptitude Test- 
ing. New York. Harpers and Brothers, 1937. 
3. Dictionary of Occupational Titles, Part I, Defi- 
nition of Titles. Prepared by United States Employ- 
ment Service, Washington: U. S. Government Printing 
Office, 1939. 
4. Hull, C. L., Aptitude Testing. Yonkers-on-Hudson. 
World Book Co., 1928. 
5. Jenkins, John G., Naval Aviation Psychology. 
I. The Field Service Organization. Psychological Bul- 
letin, 1945, 42(9), 632. 
6. Maier, Norman R. F. Psychology in Industry. 
Boston: Houghton Mifflin Company, 1946. 
7. Munn, Norman L. Psychology, the Fundamentals 
of Human Adjustment. Boston: Houghton, Mifflin Com- 
pany, 1946. 
8. Peatman, J. G. Descriptive and Sampling Sta- 
tistics. New York: Harpers & Brothers, 1947. 
9. Tiffin, Joseph. Industrial Psychology. New York. 
Prentice-Hall, 1946. 
10. Tinker, Miles A. Introduction to Methods in Ex- 
perimental Psychology, (2nd Edition). New York: 
D. Appleton-Century Company, 1947. (Chapters 1, 3, 
4, 15, 21). 
11. Viteles, M. S. Industrial Psychology. New York: 
W. W. Norton & Co., Inc., 1932 
141 CHAPTER 8 
THE PSYCHOLOGY OF ADJUSTMENT * 
“Adjust or die” is the first law of life. All 
organisms, from amoeba to man, are constantly 
busy internally and externally adjusting to the 
needs of the moment. The only organism that 
is not adjusting is the dead organism, for the 
processes of life are the processes of adjust- 
ment. 
Every medical officer has been impressed 
with the need for constant adjustment on the 
biological level. The fact that the organism is 
also constantly adjusting psychologically is not 
always so apparent. The purpose of this chap- 
ter is to point out the nature of these processes 
insofar as modern science has made that 
possible. 
THE NATURE OF HUMAN NATURE 
Science and its matter-of-fact methods have 
only very recently been turned to a study of 
human behavior. The results of the scientific 
approach to the doings of people have led to 
what may be called an enlightened confusion. 
Scientists are not yet agreed about the best 
way to explain human behavior. But every day 
the ability to understand and predict man is in- 
creasing. And scientists strongly agree that 
we will understand better and predict more 
precisely only if we adhere to two basic scienti- 
fic principles: (1) behavior is caused and, re- 
lated; and (2) behavior is to be accounted for 
in terms of natural causes. 
Scientists insist that human behavior makes 
sense. Behavior happens because things make 
it happen. Behavior is never an accidental, 
wayward, inexplicable process. It is amenable 
to cause-and-effect analysis. Although what 
people do may seem mysterious and adventi- 
tious, their actions are always caused and hence 
are ultimately predictable. 
SCIENTIFIC EXPLANATIONS 
The scientist accounts for what he observes 
in terms of scientific constructs. All the scien- 
tist can see is facts. He never sees an explana- 
tion. He observes facts and creates explana- 
tions. He creates a picture in his head of the 
processes going on behind the events he ob- 
serves. If a man were unable to open a watch 
to see what went on inside, but could observe 
only the movement of the hands, the response 
to winding and the ticking, he would soon 
create for himself some picture of what the 
entrails of the watch were like. If he observed 
the watch long enough and under enough dif- 
ferent conditions he could come out with a con- 
struct, a picture, of the dynamics of the watch. 
The construct, if it accounted for all the be- 
havior of the watch and if it were the simplest 
possible explanation, would be accepted as an 
explanation of the watch’s behavior. 
In explaining human behavior, the same pro- 
cess takes place. The psychologist observes 
what people do and creates constructs to ac- 
count for observed events. His main construct 
is the construct of need. 
NEED-CONSTRUCTS 
If you observe closely the behavior of a 
friend along about 1130 or 1200 of a typical 
day, you will probably note something like this: 
he becomes increasingly restless; the subject 
of food becomes of more and more conversa- 
* Prepared by Cdr. Alan D. Grinsted, MSC, USN. 
This chapter, with the exception of the last section, has 
been condensed and adapted from Naval Leadership, Book JJ: 
Psychology for Naval Leaders, Chs. I, III, IV: U.S. Government 
Printing Office, Washington, 1948. 
142 Chapter 8. —THE PSYCHOLOGY OF ADJUSTMENT 
tional interest; incidental things around him 
remind him of something to eat; and sooner 
or later he will make overt and direct move- 
ments toward the place food is to be found. 
You will conclude, with easy influence, that he 
is hungry. 
You haven’t seen his hunger. You’ve seen 
nothing but behavior. You read a need into 
your friend. You use a construct to explain 
his behavior. This construct is a picture in 
your head—a picture of processes going on 
behind the behavior you see. 
The need in this case stands for some com- 
plicated and unobserved goings-on in the vis- 
cera of your friend. You the observer, create 
the notion hunger to stand for these back- 
ground processes. If you say your friend has a 
sex need, or a need to dominate, or a need for 
social status, what you are doing is imagining 
something to go behind behavior. And you 
use this something, this construct, to explain 
his behavior. 
No one ever saw hunger or thirst or gregar- 
iousness or any other need. All any one can 
see in looking at people is people’s behavior. 
Sometimes we are successful, through the use 
of special instruments, in seeing some of the 
physiological or neurological processes that 
lead up to overt behavior and in such cases 
(hunger) we can be quite comfortable about 
using the need-word. We feel we are on solid 
ground. The word hunger stands for certain 
fairly well-known physiological processes. 
But sometimes we have no detailed informa- 
tion as to what processes may be behind behav- 
ior. In the case of gregariousness, for example, 
no one has ever found a muscular contraction 
or a pattern in the nervous system that can 
serve as the basis for the apparent need to 
be with people. Some people still go on behav- 
ing, however, as if they needed to be with 
people. In the case of hunger, the internal ten- 
sions lead to overt behavior, which leads to the 
taking aboard of food, which quiets down the 
internal tensions. In the case of gregarious- 
ness, a man may behave as if he had a similar 
built-in tension. He may be restless if he is 
not around people. Once there, he gives some 
evidence of feeling better. So we endow him 
with a need to be with people. A gregarious 
need is something he acts as if he must have. 
If we can predict his behavior tomorrow and 
next month by assuming he has a need to be 
with people, then the construct is a good one. 
It serves a useful purpose. 
Since no one ever saw a need, and since 
needs are products of the mind of the man 
who needs something to account for the be- 
havior of his fellows, the making of need-con- 
structs is anybody’s business. The layman 
makes up constructs and uses them to account 
for his own and other people’s behavior. He 
explains inexplicable behavior in terms of God 
or stupidity or astrological disharmonies or bad 
luck or accident or evil spirits. The psycholo- 
gists do some better, but even among psycholo- 
gists there is no complete agreement as to 
what are the most useful constructs to use in 
making sense out of behavior. But as psychol- 
ogy has grown in age and stature, the con- 
tinual process of experimentation, observation, 
and thought has distilled a group of constructs 
widely agreed upon as useful conceptual tools 
for thinking about human behavior. 
DEFINITION OF NEED 
Psychologists pretty well agree that we can 
use the construct of need in accounting for be- 
havior (some prefer the term “drive” or “mo- 
tive,” but the basic notion is the same). In 
using the term need, we will not go far wrong 
in conceiving a need to be a tension a man car- 
ries around with him. It is a tension which 
will, under the proper circumstances, lead to 
observable “seeking-behavior.” Under the in- 
fluence of an activated need a man will keep 
going until the need is satisfied. He may use 
behavior patterns he has found to be adequate 
in the past. Or he may simply thrash about 
at random. Or he may go in for what he would 
recognize as intelligent, problem-solving be- 
havior. At any rate, he keeps going until he 
finds something to satisfy the need. When he 
finds that something, seeking-behavior ceases. 
PRIMARY AND DERIVED NEEDS 
The classification of needs according to their 
dependability helps considerably in our attempt 
to come to grips with the nature of human 
nature, but it is not the only useful way of 
viewing them, not the only way of slicing the 
143 AVIATION MEDICINE PRACTICE 
cheese. Needs are frequently classed as pri- 
mary or derived (secondary). 
Primary needs are the needs rooted in physio- 
logical necessities and conditions. This cate- 
gory includes all the needs in the “most depend- 
able” class described above, with sex, obviously 
based on physiology, thrown in. We know more 
about these needs, in a way, than about the 
more elaborate needs. We have some informa- 
tion about the physiological mechanisms in- 
volved in the arousal and satisfaction of these 
needs. Because there is something solid for the 
constructs of hunger, thirst, and sex to rest on, 
some people are much happier in talking about 
these needs than about such needs as gregar- 
iousness or aggressiveness. They try to ex- 
plain human behavior in terms of these pri- 
mary tensions. Most psychologists agree, how- 
ever, that you can’t really do an adequate job 
of explaining a man’s fervent desire to become 
a big shot by referring directly to his need for 
food or love. Life is not to be so simply dealt 
with. 
Most of the primary needs can be regarded 
as vital needs—needs that must be satisfied if 
the organism is to survive. Oxygen, food, water 
must be taken into the body. The organism 
must rest sometime. But it can survive for its 
allotted years without any sexual satisfaction. 
The organism will often regard itself as un- 
happy if there is no sexual activity in its life, 
and sexual deprivation may result in peculiar 
maladjustments. But sex isn’t necessary—for 
survival. 
DERIVED NEEDS 
Most of the tensions people carry around 
with them are derived. Instead of being in- 
ternally connected with physiological neces- 
sities or preferences, they are social. They are 
learned needs, presumably derived, through 
elaborate learning processes, from the primary 
needs. The derived needs, as we have seen, may 
be relatively dependable. Gregariousness, for 
example, is a need found in almost all people. 
Most people like to be with people and are 
vastly unhappy when isolated from people. But 
while the majority is learning to like being 
with people, a minority is learning to dislike 
being with people. Like hermits. 
The needs that account for the human be- 
havior around us are mostly derived needs. 
The same derived need may be found in a vast 
majority of human beings. But that does not 
mean the need is a necessary part of man’s 
nature. It means instead that many men have 
gone through similar learning processes and 
have learned to need the same things. 
CULTURE AND NEEDS 
Man comes equipped with very few needs. 
But by the time he has lived a dozen or so 
years his needs appear so numerous and varied 
that we have a hard time even classifying them. 
The instinct psychologists used to maintain 
that man’s needs became more numerous and 
varied as he grew up because many of his na- 
tive propensities unfolded or matured only as 
the organism developed. A more sensible ex- 
planation, and one that fits the facts more 
closely, is that man learns his needs. Living in 
a certain school environment, he becomes needy 
in the ways his environment dictates. If this 
is true, his needs will vary from one social en- 
vironment to another. Such, indeed, is the 
case. 
Each individual is born into a culture. People 
around him have certain established ways of 
going about life. They know what is good, what 
is bad, what is success and failure. They have 
definite notions about morality. They possess 
established habits of work, play, cleanliness, 
lovemaking and eating. They revere certain 
institutions which they have created to meet 
common problems and common needs. These 
habits, values, assumptions, morals, customs, 
and institutions vary tremendously from one 
culture to another. The social climate in New 
Guinea is not the same as that in Tokyo, Kala- 
mazoo or Delhi. The individual must make 
peace with the culture into which he happens 
to be born. The process of making this peace 
is largely a process of learning the culturally 
endorsed needs. 
With respect to 'primary needs, the cultural 
pattern into which a person is born has a 
tremendous influence. Take hunger again. We 
can depend on it that a man will eat. But when, 
how often, and what he will eat we never can 
tell until we know how the man’s digestive 
144 Chapter 8. —THE PSYCHOLOGY OF ADJUSTMENT 
processes have been trained. In some cultures 
man experiences hunger three times a day. In 
others, people’s stomachs contract only twice 
a day. The American Indian warrior, as is 
well known, sometimes did not eat for many 
days. (We do not know whether he was really 
hungry during the time, of course.) When we 
come to what people eat—what they want to 
eat— the variation from group to group is tre- 
mendous. The Algonquin Indians consider 
skunk a delicacy. The English like sole and 
flounder. In Newfoundland sole and flounder 
are regarded as fit only for fertilizer. In Eng- 
land clams are thrown away or used for bait 
and mussels are saved for the table. In America 
clams are eaten and mussels spurned. Horse 
meat in most of Europe is standard table fare. 
In America the suggestion of eating horse 
causes some people to gag. 
In the case of sexual desire, the same sort 
of thing obtains. You can generally count on 
people to be interested in sex. But the questions 
of what sort, when, under what circumstances, 
and with whom can only be answered if we 
know something about the culturally deter- 
mined prohibitions and preferences the individ- 
ual has learned. The individual’s physiological 
needs are timed and trained by the daily routine 
of his tribe, his class, his nation, his culture. 
Little of the behavior stemming from pri- 
mary needs is free of drastic cultural influence. 
In the cas6 of derived needs—social needs— 
the role of culture is even more complete. Cul- 
ture determines the needs themselves and also 
has a determining influence on the where’s, 
when’s, and how’s of the behavioral results 
of the needs. 
THE NEEDS OF THE INDIVIDUAL 
Individuals in the same culture, even in the 
same family, differ enormously in the strength 
and variety of their needs. One man has a 
constant, burning desire to increase his profes- 
sional or military status. The need to get ahead 
is his paramount need, flavoring all his activi- 
ties, helping determine who his friends will be, 
whom he will marry, how much he will work, 
his relations with his superiors and his in- 
feriors. Another man may have such a strong 
need for sociability that he chooses friends in- 
stead of success, that getting ahead is relatively 
unimportant. One man needs food or sex much 
more often and in greater quantities than does 
another. One man spends a life seeking eco- 
nomic security while another hunts for adven- 
ture and variety. 
A knowledge of human needs in general will 
help somewhat in understanding the single in- 
dividual. But to make real predictions about an 
individual we must find out what needs will 
account for his behavior. The process of estab- 
lishing needs for the individual is the same as 
the process employed in settling on the needs 
of mankind in general. We observe the man’s 
behavior and create in our own minds a con- 
struct that will account for his behavior. If 
the observation is good and the construct is 
clear-headed, we can predict what he will do in 
a future situation. Take this example: if, on 
the basis of careful study, we conclude that a 
particular CPO has a strong need to dominate, 
we will not, if we can avoid it, put him im- 
mediately in charge of a first class petty officer 
who violently hates to be dominated. We can 
predict certain unfortunate behaviors in such 
a situation. 
THE WORKING OF NEEDS 
Later we will consider what happens when 
needs are blocked or when they conflict with 
one another. At the moment, however, our 
thinking about needs will probably be clarified 
if we get a picture of multiple interesting needs 
operating to produce behavior. Very infrequent- 
ly, if ever, can we account for a person’s be- 
havior by naming a single need—even if we 
have been forced by observation to create that 
need. Needs interact. Several needs may be 
operating at the same time. The man who is 
hungry, sexy, status-seeking, and gregarious at 
the same time will behave, if he can (which is 
rare) in such a way as to satisfy with one 
adjustment all his tensions. If these needs are 
all strong and persistent, his general way of 
life will tend to be a resultant of these needs— 
an elaborate course of action growing out of 
the many interacting tensions. The point to 
remember here is that human behavior occurs 
in something analogous to a field of forces. A 
pattern of tensions leads to resultant behavior. 
145 AVIATION MEDICINE PRACTICE 
To understand and predict human behavior we 
must contend with something more than single 
needs and simple cause-and-effect relations. 
CONFLICT 
In some situations the satisfying of a need is 
a simple process. A man with a strong need for 
food or rest may almost automatically perform 
those acts found in the past to be useful in sat- 
isfying his needs. In a very simple way the 
need leads to familiar patterns of behavior 
which very simply lead to satisfaction. Every- 
thing is fine—until the need becomes strong 
again. Then the same habitual sequence trans- 
pires again, sometimes almost identically, some- 
times with negligible variations to take into 
account minor changes in the environment. 
When the individual can turn on adequate re- 
sponses, when the need-satisfying behavior is 
all ready to go when the need-signal is given, 
life is simple. 
Very rarely does human behavior happen 
in such a simple way. We have seen that at any 
one time the individual is moved, not by a 
single need but by plural needs—maybe a few, 
maybe many. In such a case his behavior will 
be a resultant of his interacting needs. The 
behavior that grows out of an interacting pat- 
tern of needs is sort of a compromise. No 
single need can have its way entirely. It must 
give in at least a little to the demands of its 
fellow needs. This sort of process makes the 
satisfaction of needs an intricate affair. It also 
makes it next to impossible, in any realistic 
life situation, to satisfy all needs. Sometimes a 
man may adopt a course of action that will 
partially satisfy all of his needs. Sometimes he 
behaves so as to satisfy his needs one at a time, 
holding some in check while others are being 
gratified. Sometimes he may deny one need 
in order to satisfy a number of others. Some- 
times his needs are diametrically opposed, and 
the satisfaction of one means that the other will 
be permanently ungratified. 
When a man is caught in a situation where 
his needs push him in opposite directions, where 
he wants to eat his cake and have it too, he 
is in conflict. In such a situation he will do 
things that may be judged as peculiar but 
which are very human. 
THE NATURE OF CONFLICT 
The individual is almost continually getting 
himself into situations where he must choose 
between eating his cake and having it too. The 
conflicts vary from highly charged ones, where 
strong needs are involved, to mild little conflicts 
where an easy choice comes immediately. Our 
pattern of needs is so complicated that only 
rarely can we react wholeheartedly to one of 
life’s situations. Almost anything we do or 
seek has its advantages and disadvantages. “I’d 
like that . . . but . . .” is the characteristic 
feeling about a majority of the things we seek 
or think about seeking. That “but” is an in- 
troduction to the disadvantages. 
TYPES OF CONFLICT 
We can roughly classify conflict into several 
types. The first type is exemplified by the sex 
dilemma of the individual whose thoughts make 
the brothel attractive and repulsive at the same 
time. In our daily lives this sort of conflict is 
very frequently encountered. We want to suc- 
ceed in our chosen career but succeeding in 
that career means hard and often disagreeable 
work. We want to marry but wives mean re- 
sponsibilities. We want sea duty but sea duty 
may mean long absence from many friends. We 
like to drink but drinking means hangovers. 
In many—maybe most—life situations we have 
to take the bad along with the good. Such con- 
flicts become serious, leading to real indecision, 
only when the goods and bads are strong—and 
approximately equally strong. 
A second type of conflict occurs when we 
have to choose between two equally attractive 
courses of action. Shall we go to the dance or 
go to the movies? Shall ve marry Mary or 
Marie, both of whom are ready, willing, and 
attractive? Shall I spend my extra money on 
a Cadillac or a yacht (or on a coke or a root 
beer) ? Having to choose between two equally 
pleasant courses of action is the most desirable 
sort of conflict to get into, of course, but it still 
can interfere, at least momentarily, with the 
smooth and effective flow of behavior. 
Then there is the less agreeable sort of situa- 
tion where we must choose between two unat- 
tractive courses of behavior. Since my uniform 
hasn’t come from the cleaners, shall I get it 
146 Chapter 8. —THE PSYCHOLOGY OF ADJUSTMENT 
and report to duty late but pressed, or shall I 
report on time and unpressed? 
REACTIONS TO CONFLICT 
When an individual is caught in a conflict 
situation the smooth and adaptive flow of be- 
havior is interrupted. Various sorts of things 
happen. 
Paralysis.—If the conflict is severe, the in- 
dividual may simply “freeze.” He is unable to 
do anything. The story is told about the jackass 
who found himself exactly half way between 
two piles of hay. Unable to decide which to 
eat, he starved to death. This sort of paralysis 
does happen in everyday life—though rarely 
is it connected with the choice between two 
equally attractive courses of action. It is likely 
to occur when there is ambivalence—where 
something is attractive and repulsive at the 
same time. 
Many cases of so-called laziness are probably 
explainable as paralytic reactions to conflict. 
The lazy man, if he is studied carefully, often 
turns out to be the man who is in conflict. He 
wants to achieve, but the road to achievement 
looks very tough and thorny. Or he may fer- 
vently desire success but at the same time feel 
that his chances of failure are so great that he 
is afraid to try. Hard work is good in that it 
may lead to success. But it is bad in that it 
will probably lead to failure. In such a con- 
flict a man is likely to just sit, being miserably 
unhappy and, to the common-sense observer, 
lazy. 
This sort of conflict often has a lot to do 
with personal efficiency. Most men will work 
as long as work promises to get them some- 
where. They will not work when work promises 
to bring failure, or only small rewards, or 
downright punishment. 
During the war a group of officers became in- 
terested in morale among naval aviation cadets 
in intermediate training. In anonymous inter- 
views the cadets were asked this question: “At 
one time or another in your life you have prob- 
ably had a job at which you worked with great 
enthusiasm and efficiency, where you felt you 
were working at your best. If you rate your 
best work efficiency at 100 percent, what would 
you say your present work efficiency is?” The 
cadets appeared to have no difficulty in under- 
standing the question and the interview situa- 
tion was staged so that honest answers were 
likely. They put their present efficiency any- 
where from 40 to 100 percent with the average 
around 65 percent. This means that the average 
cadet was performing at what he judged to be 
35 percent below his peak. 
There was no doubt that these cadets were 
anxious to get their wings, and most of them 
appeared genuinely to want combat duty—to 
“get out where men are men.” Why, then, were 
they not working with peak efficiency toward 
their goals? There were probably several fac- 
tors. But in accounting for personal inefficiency 
in seeking a highly desired goal, a likely place 
to look for reasons is in the promises held out 
by hard work. Does it promise success and 
rewards? Or does it promise failure and pun- 
ishment? In this case, what factors are there 
driving the cadet away from hard work? Inten- 
sive interviewing suggested two related nega- 
tive factors: (1) the pervasive fear of failure, 
and (2) a fear of unfair evaluation of work. 
Failure in flight training was a traumatic 
thing to the average cadet. Many flight-failures 
were practically ready for suicide. And the 
possibility of failure was kept continually up- 
permost in the minds of cadets. Instead of 
being a chance to learn, to demonstrate skill, to 
get on toward the goal, every flight, every hour 
of ground school, became a fearsome chance 
to flop, to fail, to get a down. This pervasive 
fear of failure was enhanced by the cadet’s 
feeling that success or failure was often an 
accidental matter. 
In such a situation, real efficiency is highly 
unlikely. Every hour of work involves high- 
level conflict. The cadet desperately wants to 
succeed. He desperately fears failure. If at any 
moment, the possibility of failure seems equal 
to or greater than the possibility of success, 
a man just cannot get wholeheartedly involved 
in work. Of course, any time he tries to succeed 
at something he must take the bad with the 
good, he must suffer some, he must run some 
risk of failure. If the suffering and risk seem 
greater than the rewards of success, however, 
no effort will happen. If the disagreeable as- 
pects of work are too strong, if it looks to him 
as if the reward, instead of fitting the effort 
147 AVIATION MEDICINE PRACTICE 
and the performance, is a matter of luck, his 
behavior will be continually jittery, inefficient, 
conflictful. If the chances of success are reason- 
ably good, if it appears that success is not ac- 
cidental but fairly and inevitably dependent 
on high effort and good performance, personal 
morale will be high and work will be efficient. 
The hardships of work will be taken in stride. 
In less involved situations, where individuals 
are caught in a paralytic conflict, the flow of 
behavior may be only momentarily interrupted. 
We have all had fleeting moments of indeci- 
sion arising out of small conflicts. We generally 
have little trouble in reaching a decision. What 
happens is that one need becomes stronger than 
the other and behavior—as always—follows 
the strongest need. 
There are those of course who will continue 
to say that the conflict-bound individual is 
just lazy. And they say that so-and-so, being 
lazy, needs nothing so much as a good swift 
kick in the bosom of his britches. Such a 
diagnosis is never adequate and such a treat- 
ment, while it may produce activity of some 
sort, will hardly result in enthusiastic work. 
Work happens when work promises rewards to 
the many needs of the worker. Work will not 
happen if it promises frustration and unpleas- 
antness. Generally speaking, the more reward- 
promising the work, the more enthusiastic the 
worker. If the rewards outweigh the handi- 
caps, the handicaps will be taken in stride. 
Alternation.—A second reaction to conflict is 
alternation. The person in conflict may try one 
course of action a while, then turn to the other. 
The hungry rat who can only get food by cross- 
ing an electric grill that shocks him pretty 
viciously will often go toward the food ’til he 
gets close to the grill. Then he retreats from 
the grill. This alternate approaching and re- 
treating may go on until hunger gets strong 
enough to make the shock a thing to be taken 
in stride. At a considerably more complex level 
there is the example of the man in serious 
conflict about morals and religion. One week 
he was strictly a churchman, strictly a moralist. 
The next week he would become a confirmed 
rounder. 
In everyday situations we encounter less dra- 
matic instances of alternation. With respect 
to the sort of work-conflict we have been talk- 
ing about, for example, the person may alter- 
nately work with great zest and loaf with com- 
plete flaccidity. 
Escape.—The person in conflict frequently 
behaves in such a way as to avoid having to 
make a choice. If I stay in this billet I am 
likely either: (a) to get in trouble with my 
men, or (b) to have to be relentlessly hard- 
boiled with them. Both courses of events are 
distasteful to me. I will request a change of 
duty. This is an easy escape from conflict. 
Sometimes this sort of escape from the arena 
of conflict is very wise. Doctors who recom- 
mend a change of scene, such as a summer in 
the mountains or a trip to Europe or a winter 
in Florida, are often simply arranging for the 
patient to escape temporarily from a situation 
that throws him into a tense and debilitating 
conflict. 
Physical escape from the conflict situation is 
frequent and often adaptive. There are psy- 
chological escapes, too, and these may not be so 
conducive to the maintenance of mental health. 
The individual may dream up for himself a 
fantasy existence wherein the harsh realities of 
a conflictful world fade away. This and other 
sorts of escape reactions will be treated in more 
detail later. 
Problem Solving.—Instead of coming down 
with paralytic inactivity, instead of alternating 
between one response and another, instead of 
physically or mentally escaping the conflict, the 
individual may find a way to resolve the con- 
flict so he can, in effect, have his cake and eat 
it too. This, of course, is the smart way out of a 
conflict. 
Actually a physical escape from the conflict 
situation is a solution—of a sort. The only 
trouble with it is that it is likely to be tempor- 
ary. The emotionally upset individual who re- 
quests sea duty to escape a conflictful home 
situation may be playing ostrich. He sticks 
his head in the sand and his conflict ceases. 
But he has to come up for air sometimes. When 
and if he does, there is the conflict again. He 
hasn’t solved his problem. He has only ignored 
it a while. Perhaps, by virtue of some rest 
and change of scene, he will return to it with 
greater ability to wrestle intelligently with it, 
but the problem is still there. 
148 Chapter 8. —THE PSYCHOLOGY OF ADJUSTMENT 
A lot of conflicts, once a choice is made, tend 
to solve themselves. Perhaps, while young and 
inexperienced, a young man is equally attracted 
to West Point and to Annapolis. Suppose he is 
fortunate enough to be able to choose which 
he will attend. He finds decision impossible. 
He flips a coin. It sends him to Annapolis. 
Once he takes steps toward Annapolis, West 
Point probably loses its attraction for him. 
Once he makes a decision and begins to act on 
it, the opposing interest falls into the back- 
ground. He identifies with Annapolis and rarely 
will he have regrets involving a comparison 
of the Severn and the Hudson. (P.S. If the coin 
had fallen the other way, he would have been 
ultimately just as happy. Either course of ac- 
tion satisfies the basic needs involved. Such a 
conflict is a conflict of means, not of ends.) 
In many conflicts, particularly those involv- 
ing choice between two good things, any choice 
is a good solution. In other conflicts, however, 
no choice is really a good choice. Compromise is 
a necessary and unsatisfactory course of action. 
The man who wants sea duty but violently fears 
seasickness, applies for duty involving only in- 
shore patrol. The man who is fascinated by air- 
planes but fears to fly seeks a position as 
ground-school instructor or aviation mechanic. 
Much of our lives we live by compromise. 
We cannot have our cake and eat it too, so we 
figure out clever ways to have some and eat 
some. If we can’t eat our cake, we find some- 
thing else almost as good to substitute for it. 
We cannot expect to avoid conflicts. Life is full 
of them. We can hope to (a) diagnose our con- 
flicts properly, and (b) go intelligently about 
the business of finding the best possible solu- 
tions for them. 
Where do conflicts come from? The more im- 
portant conflicts result from our acquiring in- 
compatible needs or incompatible behavior 
mechanisms. Some conflicts, however, arise out 
of the way the human organism is equipped at 
birth. It is impossible, for example, to flex and 
extend a limb at the same time. It is very diffi- 
cult to rub your stomach with one hand while 
patting your head with the other. Exerting 
maximum grip with the right hand seems to 
prevent maximum grip with the left, and you 
cannot, of course, look to the right and to the 
left at the same time. The structure and 
functioning of the body and nervous system 
make certain small-time behavioral conflicts 
inevitable. But the conflicts that tie us in emo- 
tional knots are the ones growing out of our 
derived needs. 
It has been observed that our modern culture 
is particularly likely to breed conflicts in in- 
dividuals. 
Conscience vs. Old Adam.—The sort of con- 
flict that the psychiatrists and psychoanalysts 
make much of is the battle between our primi- 
tive desires and our consciences. We are born 
with needs for food, sex, etc. Through learning, 
we develop a conscience whose function is to 
guide us into socially acceptable ways and 
means of gratifying our basic needs. In many 
of life’s day-by-day situations, the learned pro- 
hibitions and restrictions of conscience do bat- 
tle with the primitive unlearned animal needs. 
Conscience, in most of us, wins fairly consis- 
tently, When conscience is very strong, con- 
flict, at least at the conscious level of tempta- 
tion, rarely happens. If conscience is very weak 
or non-existent, the Old Adam is pretty free 
to express himself, and there is not much con- 
flict in such a situation- either. But when our 
needs are just about as strong as conscience, 
conflict can be severe. 
In our particular culture such conflicts be- 
tween needs and conscience are very often 
centered around sex. In most men sex is a 
strong need. It is probably made stronger and 
more important by the standard attitudes to- 
ward it. The parents who deliberately or other- 
wise teach their children that sex is a nasty, 
hush-hush affair are incidentally teaching their 
children that it is a fascinating business. The 
devices intended to control sexual behavior 
often work to make sex harder to control. But, 
however strong our sexual needs, our culturally 
engendered conscience is usually able to exer- 
cise control. When the control weakens, how- 
ever, highly charged conflict results. Out of 
these conflicts grow such things as impotence 
or frigidity, guilt feelings, anxieties, and com- 
promise perversions. 
Our culture sets the stage for sexual con- 
flicts by teaching a set of prohibitory rules 
designed to control primitive needs. It also 
tends to teach us goods that are sometimes 
mutually exclusive. “A wife and a family are 
149 AVIATION MEDICINE PRACTICE 
fine things,” says the culture, “but don’t get 
married until you can afford it and be careful 
that your family doesn’t take up time you ought 
to be spending at your proper business of get- 
ting ahead.” The individual who has learned to 
need a family and learned to need success has 
something of a conflict on his hands. He must 
wait, compromise, and often suffer in order 
to meet these two needs. If he goes whole- 
heartedly after establishing a family, he will 
not have time to compete successfully with his 
fellow succeeders. If he is wholehearted in 
plying a profession, he will neglect his family. 
He must evolve for himself some halfway pat- 
tern of life that enables him to have some cake 
and to eat some. 
The culture teaches us many of these “but” 
propositions, each containing a built-in conflict, 
each demanding some complex problem-solving 
adjustment if we are to avoid extreme emo- 
tional difficulty. 
FRUSTRATION 
The environment we live in is by no means 
tailored to the needs of any one person. When 
a complex individual wrestles with a complex 
life, it is inevitable that he will be thrown into 
conflicts. It is also quite certain that many of 
his needs will be thwarted. He will want things 
that he cannot, for one reason or another, have. 
Frustration, in modern life, is frequent and un- 
avoidable. 
Frustration occurs when need-directed be- 
havior is blocked. In the simplest case of hu- 
man behavior we have seen how a need arises, 
adaptive behavior patterns are turned on, sat- 
isfaction is achieved, and the need-tension dis- 
appears. But we have seen, too, that only 
rarely is life so simple. Conflicts interfere with 
the basic natural process. More cluttering is 
introduced if some barrier arises to keep the 
organism from going where it wants to go and 
doing what it wants to do. 
When a man wants something he can’t get, 
whether that something is as trivial as a lost 
pencil or as all-important as pre-eminence in 
his profession, he is frustrated. And when he 
is frustrated, the simple directness of his be- 
havior disappears. He characteristically be- 
comes quite emotional. And his reactions, though 
they serve a psychological function, may get 
him nowhere at all. To the casual outside ob- 
server, the behavior of a frustrated man may 
make no sense whatsoever. But frustrated be- 
havior is very human behavior and the man 
who is going to predict and control human 
beings will do well to understand something 
about it. 
THE BARRIERS WE MEET 
The people, objects, and situations that get in 
our way as we struggle to satisfy our needs are 
almost infinite in number and variety. But we 
can talk about them in terms of six general 
types: 
Strictly impersonal barriers.—The man who 
is in a hurry to go out but is unable to get 
his apartment door unlocked presents a good 
picture of frustration. He may try various 
alternate ways of getting out and if none of 
them work, he can be counted on to become 
agitated and angry. The cancellation of a sched- 
uled airline flight, the reddening of a traffic 
light, physical distance, fences, walls, busy 
telephones, malfunctioning engines, low tides 
and thousands of other impersonal objects can 
be counted on to interfere with the day-to-day 
attainment of our goals. 
People as people, frustrate us.—People, prob- 
ably more often and more disturbingly than in- 
animate objects, hem us in and obstruct the 
attainment of our goals. People, of course, 
facilitate our goal-seeking behavior too, but 
when each person has his own needs to worry 
about, it is inevitable that people are going to 
get in one another’s hair. We can expect al- 
most any human association—even friendship 
or marriage—to be frustrating at least some of 
the time. Friends and wives are quite often 
good things to have around. They satisfy many 
needs. But friends and wives are people. They 
have their own needs. And when a friend’s 
needs or a wife’s needs run counter to our own, 
somebody is going to be frustrated. And since 
marriage and friendship are fifty-fifty affairs, 
the friend or the wife can’t be expected to bear 
more than half the load of frustration. 
People, as enforcers of rules, frustrate us.— 
When any group of people live together— 
whether as a culture, a nation, a Navy, or a 
150 Chapter 8. —THE PSYCHOLOGY OF ADJUSTMENT 
crew—there have to be certain rules about 
who shall do what when. These rules are ex- 
pressed as morals, taboos, laws, and regula- 
tions. The completely civilized man wants to 
live in the way the many rules and regulations 
suggest. But few, if any, of us are so com- 
pletely civilized that the rules, laid down for 
the long-term welfare of the many, do not 
seriously interfere with what we, as indivi- 
duals, want. These rules are enforced by people. 
There are policemen, upholders of morality, 
standers - for - the - right, commanding officers. 
These people deliberately or unintentionally en- 
forcing the rules the group lives by, sometimes 
block the personal inclinations of the individual 
member of the group. 
Being frustrated by a person, whether that 
person is merely an individual trying to get 
along or a symbol of law, order, and propriety, 
is generally more disturbing than being blocked 
by an inanimate object. In the first place, peo- 
ple are harder to figure out than a door that 
won’t open. In the second place, they are sup- 
posed to be more sympathetic and understand- 
ing than inanimate objects. We expect them 
to be reasonable and kind; when they aren’t, 
our frustration may be increased. In the third 
place, if we do what comes naturally under 
frustrating circumstances and attack the bar- 
rier, the human barrier can fight back. It can 
hurt us physically or professionally, make us 
feel guilty, make us ashamed of ourselves. We 
can kick a door in the shins without any seri- 
ous psychological hangover, but any venting 
of anger on a human being is likely to produce 
a very complicated aftermath. 
Our inabilities frustrate us.—Sometimes we 
seem to be our own worst enemies, for our de- 
sires are now and again blocked by factors 
we carry around with us. One built-in frus- 
trating factor is plain inability—plain lack of 
physical or mental capacity to do what we want 
to do. Think of the healthy man who loses an 
arm or a leg or some other frequently em- 
ployed anatomical appendage. He is bound to 
experience frustration. The boy who wants to 
be a college athlete but under no circumstances 
can get his scales to read more than 125 pounds 
is very likely to suffer almost excruciating frus- 
tration and defeat. Mental incapacity also pro- 
duces frustration. Every year thousands of 
young men enter American universities, opti- 
mistically heading for law or medicine or en- 
gineering, but discovering sadly, after a few 
months of realistic exposure to life and higher 
education, that they just do not have the neces- 
sary ability to reach their professional goals. 
In many situations the individual’s plans and 
expectations overreach his abilities. Through 
the influence of doting parents, or through an 
unrealistic self-appraisal, he hitches his wagon 
to a star. When his wagon turns out to be too 
rickety for the journey, defeat, bitter and dis- 
turbing, is upon him. When an individual’s 
level of aspiration is too far above his level of 
achievement or his level of abilities, frustration 
is the result. 
Conflicting positive motives lead to frustra- 
tion.—We have seen that in situations involv- 
ing conflict the individual must often choose 
one course of action and deny another. Or he 
must achieve a compromise which partially de- 
nies both of his conflicting needs while partially 
gratifying each. The partially or wholly denied 
need cannot be counted on to disappear. It stays 
around, sometimes with great insistence. If 
a course of action gratifying the first need 
makes gratification of the second impossible, 
the second need is frustrated and influences the 
organism’s behavior accordingly. 
We have seen that often when a man makes 
a choice between two attractive things, the 
denied attraction loses potency the farther he 
gets away from it. The man who decides to 
go to Annapolis instead of West Point is not 
often frustrated by not being at West Point 
once he is involved in life at Annapolis. But 
this really is a fairly superficial conflict. The 
basic needs involved (status, perhaps) can 
possibly be satisfied equally well be either of 
the two courses of action. But when we put a 
man in a situation where strong basic needs 
are in diametric conflict, one need will be frus- 
trated. The man who finds that he can bring 
about the sort of status he needs only by achiev- 
ing priesthood, but who, on the other hand, 
has strong primary needs for worldly things, is 
in highly charged conflict. If he dons the cloth, 
his red-blooded needs are going to be frus- 
trated. If he adopts a way of life wherein red- 
bloodedness is more possible, his needs for a 
high religious status will be forever blocked. 
151 AVIATION MEDICINE PRACTICE 
He’s in for a tough and troublesome life what- 
ever he does. 
A positive need vs. a negative one produces 
frustration.—Here again, conflict leads to frus- 
tration. The case of laziness comes again. The 
man who wants to lick the world, but is locked 
in inactivity because of fear of failure or fear 
of unfairness of competition or fear of his own 
inabilities is a frustrated man. His behavior, 
what there is of it, will more than likely be 
characterized by a tense, dissatisfied grumpi- 
ness. 
Often the negative needs in positive-negative 
conflicts are needs flavored with fear. The fear 
of what people will say, the fear of being 
caught and punished, the fear of making a fool 
of oneself. These blocks can frustrate positive 
needs, often more effectively and more disturb- 
ingly than any impersonal or external barriers 
yet invented. 
Closely related to the barriers of external 
social pressure are the conscience-barriers that 
the average man possesses. When any highly 
desired course of action conflicts with a man’s 
code or conscience, or with the role he pictures 
for himself, frustration is likely. If, in time of 
temptation, the person’s conscience is stronger 
than the conscienceless need, there will be no 
real conflict and no severe frustration. Or, 
if conscience is very weak, a man may steal, 
cheat, or rape with equanimity. But when con- 
science and need are both strong, something 
is going to be frustrated. If the man steals, he 
has the money, but he has a guilty conscience, 
feelings of shame, and remorse. If he follows 
his code, he hasn’t the material rewards of sin- 
ning. The man who gets to be a success by 
ruthless competition may have a large income, 
but at the same time he feels the sort of uneasy 
guilt that makes him into a showy philanthro- 
pist. The man who refuses to play according to 
ruthless rules may have a clear conscience and 
a frustratingly small bank balance. 
In our society—in any society—the rules, 
regulations, disciplines, and institutions estab- 
lished to make it possible for people to live to- 
gether without too much friction will often 
block the private needs of the single individual. 
When the rules, regulations, standards, and 
values of a society become a part of the in- 
dividual’s conscience, the blocking of needs 
still happens. If the individual’s conscience and 
code become very strong, he may experience 
no conscious conflict with his baser motives. 
But there is some reason to believe that in 
many cases the individual with the most iron- 
clad conscience still is influenced by his frus- 
trated primary needs. This is a point we will 
need to consider again later. 
REACTIONS TO FRUSTRATIONS 
When an individual on his way to a goal 
confronts a barrier—whether it be of an im- 
personal or of a built-in, personal nature—his 
first behavior will generally be of a problem- 
solving variety. He will scratch around to find 
some way to circumvent the obstruction. If his 
attempts to be smart about his problem all lead 
to failure, behavior soon moves out of the intel- 
ligent, problem-solving category and becomes 
emotional. The child who is placed in a room 
where he can see a bunch of fascinating new 
toys but is kept from them by a fence, will first 
seek a way around or over the fence. When he 
fails at this, frustration continues and the be- 
havior that ensues becomes emotional and, to 
an outside observer, strictly strange. There are 
a variety of reactions to frustrating situations : 
Aggression.—Probably the most frequent re- 
sponse to frustration is one of anger and attack. 
The child, in the situation above, may charge 
angrily into the fence. Or his aggression may 
be of the nondirected type you can often see 
in children’s (and sometimes in adults’) temper 
tantrums—a wild and angry and ineffective 
slashing away at any object within reach. If 
the frustration is produced by a person, the 
attack may be directed at that person. If the 
frustration is due to the individual’s own in- 
capacity, the aggression is turned inward—the 
person will think and say derogatory things 
about himself and may devise ways to make 
himself suffer for his shortcomings. 
Aggression may take several forms. In chil- 
dren, the direct frontal attack involving physical 
blows at the object or person, is fairly fre- 
quent. In adults, such crude aggressions are 
often refined into verbal substitutes. The adult 
will sometimes kick a bothersome chair in its 
shins or pommel a person who gets in his way. 
Fist fights, wife-beating and such physical ag- 
152 Chapter 8. —THE PSYCHOLOGY OF ADJUSTMENT 
gressions do happen in adult society, but most 
often we aggress—particularly against people 
—by more intellectual devices. We call names, 
or we ruin character, or we spread scuttlebutt, 
or we withhold approval, or we play practical 
jokes, or we haze. Man has a pretty complete 
collection of subtle devices for making his fel- 
low man suffer—when his fellow man frus- 
trates him. 
Aggression may not always be a direct at- 
tack on the object or person that is doing the 
frustrating. There is such a thing as misplaced 
aggression. The man who comes home after a 
day during which his CO has strongly disap- 
proved of his work, his fellows have demon- 
strated a definite coolness to him, and his every 
attempt to achieve belongingness and effective- 
ness at his job has met with failure, can be 
counted on to go in for fairly bearish behavior. 
He may walk in the house, kick the cat, damn 
the dog, slam his coat on the floor and belittle 
his wife’s ability as a cook. The pent-up steam 
of aggression is vented upon things and people 
who had nothing to do with the frustration that 
produced the aggressive tendencies. 
This sort of misplaced aggression is fre- 
quent. It often has serious consequences. The 
aggression may be misdirected because of two 
reasons: (1) the individual may not be able to 
diagnose and understand what is frustrating 
him; and (2) the individual may know what is 
frustrating him, but also knows that it is very 
unwise to attack the frustrating object or per- 
son. 
There are many frustrating situations in 
which he cannot understand what it is that’s 
causing our trouble. In time of depression, for 
example, though frustration is widespread, we 
are unable really to appreciate the complicated 
and interlocking economic factors that cause 
the distress. And even if we did understand, 
there would be no way of attacking an eco- 
nomic cycle or overexpansion or excessive in- 
ventories. The frustration is concrete, never- 
theless, and our tendency to aggression is pres- 
ent and strong. So we very often find something 
or someone to blame. The President is a handy 
person to blame; Congress, too. And in hard 
times the President and Congress, who prob- 
ably have only a negligible part, if any, in 
causing our troubles, are viciously berated in 
the press, in drawing rooms and in pool halls, 
and very often they are turned out of office. 
During war, when frustrations are plentiful 
and hard to diagnose, the aggressions of the 
people are turned on all sorts of concrete get- 
at-able and relatively blameless stimuli. The 
President and Congress are always there as 
lightning rods to catch our aggressions, and 
there’s the Navy, the Army, the Jews, the mu- 
nition makers, the Negroes. All these, in time 
of national duress and frustration, catch more 
hell than they deserve. Aggression will out. 
If we can’t put our finger on the causes of our 
troubles, we’ll pick on something or somebody 
else. 
The well-known phenomenon of scapegoating 
is accounted for in terms of misplaced aggres- 
sions. When frustration is extreme and the 
source of frustration is either unknown, un- 
available, or unsafe to attack, there is a ten- 
dency to pick a “goat” to visit our aggression 
upon. In any group, the scapegoat phenomenon 
can be expected to occur if the situation is right. 
If the members of a crew are frustrated, they 
may pick a certain member of the crew or oc- 
casionally a junior officer to focus their aggres- 
sion upon. The officer or man who becomes 
scapegoat will usually be one who (1) is get-at- 
able, (2) cannot fight back successfully, (3) is 
“different” from his fellows, and (4) appears, 
at least superficially, to deserve ill-treatment. 
Any crew in the Navy is trained to bear up 
under certain necessary frustrations. But in 
any circumstance where the crew is denied too 
many satisfactions—if liberty is too long re- 
stricted, if pride in the unit is impossible, if 
conditions of work lead to uncertainty, insecur- 
ity, and a feeling that rewards and punishments 
do not make equitable sense—aggressive atti- 
tudes can be expected. And, conversely, when 
the crew or any of its members becomes em- 
broiled in group or private aggression, you can 
profitably start an immediate search for frus- 
tration. The aggressions of a frustrated crew 
may take the form of recalcitrance in the 
presence of officers, the choosing of a scapegoat, 
outbursts of fighting on board or ashore, gen- 
eral surliness, and refusal to work. 
We have seen that aggressiveness is a wide- 
spread form of human behavior. We have also 
seen that it is not a universal form of human 
153 AVIATION MEDICINE PRACTICE 
behavior. Evidence indicates pretty clearly that 
aggressive behavior happens only as a result 
of frustration. While frustration may produce 
other than aggressive behaviors, aggressive be- 
havior—whether in the group or in the in- 
dividual—can always be traced back to frustra- 
tion. This generalization is one of the most 
helpful the leader can learn. It will guide him 
on numerous occasions in the diagnosis and 
control of human behavior—his own included. 
Regression.—The child who sees lovely and 
unobtainable toys on the other side of an im- 
passable barrier may first attack the barrier. 
Then, experimental observations have shown, 
he is very likely to go in for play activities that 
characterize a much younger child. He re- 
gresses. In the face of frustration he adopts 
patterns of behavior that he used years ago. 
Children, of course, are not the only people 
who regress. Some shell-shock patients regress 
to infancy and must have their diapers changed 
and their bottles equipped with nipples. More 
normal instances of this sort of behavior occur 
every day. Often in tough and frustrating situa- 
tions, adults will behave childishly. The temper 
tantrums in adults may be regarded as an at- 
tempt to use a procedure once adaptive in hand- 
ling troublesome parents. 
Adults, when confronted with frustrations, 
also go in for other childish symptoms. They 
sometimes pout. They sometimes cease think- 
ing and go in for broad, emotional, childish 
generalization. They feel and articulate a de- 
sire to return to the “good old days.” When 
any adult starts wishing for the bygone days, 
the days when life was simple, you can gener- 
ally bet he is finding his present problems a 
little beyond his ability to solve. 
Apathy.—The frustrated individual, hemmed 
in by barriers and confronted with continual 
failure may sink into a state of hopelessness 
and apathy. He gives in, quits trying, con- 
vinces himself he doesn’t care. This sort of 
apathetic resignation has been observed in such 
people as prisoners of war, Europe’s displaced 
population, the chronically unemployed, the 
hopelessly crippled. It is an attitude of com- 
plete surrender. The individual, unable to work 
out any sort of adjustment to a bitter and hos- 
tile environment draws into himself, quits try- 
ing, becomes passive, gives up. The mental 
patients classified as involutional melancholias 
have reached an extreme stage of apathy and 
depression. In normal cases, we encounter a 
sour and pessimistic view of life, a depressed 
expectation of nothing good. 
Fixation.—Sometimes the individual reacts 
to frustration by falling into repetitive, stereo- 
typed patterns of behavior. This sort of reac- 
tion is known as fixation—a compulsive contin- 
uation of behavior that apparently doesn’t get 
the organism anywhere. A rat, if put into a 
problem situation where no answer is possible, 
but where some sort of answer is strongly 
needed, may resort to such maladaptive fixa- 
tions as bumping his head repeatedly against 
a cage door without even trying the next door, 
one that would let out his dilemma. Human 
beings do the same sort of thing. 
Probably the most interesting sort of human 
fixations occur on the intellectual level—in the 
thinking of people. The man who fixates in 
such a fashion is not the man who meets new 
problems with an open mind and a vigorous 
optimism. He resists new problems. He will 
not even listen to new solutions to old problems, 
for objective listening would demand objective 
evaluation, a process he finds psychologically 
painful. He already knows. He accepts new 
information only when it agrees with what he 
knows. He has what Wendell Johnson has called 
the “Maginot Line Mentality.” 
Repression.—When conscience does battle 
with conscienceless needs, the resulting emo- 
tional stew is highly flavored with guilt and 
shame. If conscience is strong, the need, of 
course, is frustrated. But because the individual 
is ashamed to admit that he could have such 
a need, the frustration is different from other 
sorts of frustration. The man who esteems him- 
self as highly honorable and respectable is 
seriously disturbed if he realized he is strongly 
tempted to steal, to rape, or to commit some 
act equally foreign to the complimentary pic- 
ture he has painted of himself. In such cases 
he can restore his self-esteem only if he can 
forget the temptation, pretend it never hap- 
pened. Very often in such cases of conflict be- 
tween the Old Adam on one hand and self- 
esteem on the other, the basic need is not only 
frustrated, but is also repressed, is shoved out 
of conscious memory. 
154 Chapter 8. —THE PSYCHOLOGY OF ADJUSTMENT 
This notion of repression is strange to most 
people, but to give it credibility, all we have 
to do is to observe the convenient way our 
memories work. How much more often do we 
remember incidents of which we are proud 
then we do incidents of which we are ashamed ? 
The former sort of event we keep fresh by tell- 
ing people about it. The shameful incident we 
let slide into oblivion by not even telling our- 
selves about it. Eventually it may be lost en- 
tirely to memory. When the shame and guilt 
are multiplied, the tendency to forget, to re- 
press, is magnified. 
The needs thus repressed, though no longer 
recognized consciously by the individual, do 
not cease to influence behavior. Needs do not 
disappear, tensions do not dissipate, simply 
because we prefer they not exist. According 
to one theory (the psychoanalytic theory) re- 
pressed needs live on in the realm of the un- 
conscious and not only influence later overt 
behavior, but reveal themselves in fantasy life 
and in the elaborate symbolism of dreams. 
These distasteful needs, the theory goes, are 
often projected into other people. We tend to 
see in other people those unseen and disagree- 
able repressed needs we ourselves have. This, in 
simplest terms, is the old notion that it takes 
a thief to know a thief. It has often been ob- 
served that people who expect the worst of their 
fellow men, who see sin where other people do 
not, are people with the most strait-laced con- 
sciences. The man who busies himself with 
other people’s morals, who combines suspicion 
with a puritanical code of behavior, may be 
the man who has done the most repressing of 
his own wayward needs. Often, too, the man 
who crucifies the sinner most unmercifully, 
usually in the name of religion or ethics, is, by 
punishing the transgressor, at the same time 
telling himself that his own repressed needs are 
horrible things and had better stay repressed. 
The too obvious, the too blatant, the too in- 
tolerant conscience, according to the psycho- 
analysts, is a good sign of extreme and un- 
healthy repression of normal tendencies con- 
cerning sex, elimination, or aggression. 
Substitute goals.—The frustrated individual, 
denied one goal, may cast about for something 
almost as good. The man who wants to be 
a naval aviator but who washes out of flight 
training may enter aerial navigation and at 
least partially satisfy his needs. The man who 
wants to play football may, after a season of 
sitting on the bench, turn his energy to soccer 
or lacrosse where his abilities are more ade- 
quate. Such adjustments to frustration gener- 
ally make good sense. Certainly the reflection 
of energy into constructive and compatible 
paths is more rational than scatterhead ag- 
gression or apathetic resignation. 
Where the frustration is due to some physical 
or mental disability, the original energy some- 
times appears greatly increased, and when 
turned loose on substitute goals leads to great 
accomplishment. This is called compensation. 
Theodore Roosevelt is one of the best known 
examples of this reaction to frustration. A 
puny child, he conditioned himself unmercifully 
until he became the rough-riding picture of 
virility. Then there is the homely girl who be- 
comes an excellent conversationalist, or the 
pimply-faced boy who develops great skill in 
ballroom dancing. And there’s the officer who 
fails miserably at shore-based administration 
but who becomes remarkably proficient as a 
destroyer skipper. 
The basic need in most cases, of course, is the 
need for status and acceptance. When one road 
to status is blocked, the adaptive thing to do is 
find another way. When the second way is 
found, the travelling thereon seems more ener- 
getic by virtue of having encountered a few 
rocks on the first. 
Escape.—The individual who meets with fail- 
ure in his attempts to satisfy his needs may, 
as in the case of conflict, seek to escape. Es- 
capist activity can be physical or it can be psy- 
chological. The person may physically hie him- 
self away from the frustrating situation or he 
may psychologically do the same thing by cre- 
ating for himself an imaginary world where all 
is serene and he reigns supreme. 
Some highly active people, when caught in 
the throes of frustration, appear prone to get 
physically away from the predicament. They 
go to California, or quit their jobs, or catch a 
plane for Reno, or go home to Mother, or join 
the Foreign Legion, or sign on as a deckhand 
on an Oriental freighter, or they go a.w.o.l. 
Other individuals appear to prefer psycho- 
logical escape into realms of rich and satisfying 
155 AVIATION MEDICINE PRACTICE 
fantasy. Daydreaming is an almost universal 
pastime. We all meet frustrations; we all, at 
least occasionally, dream up wishful fantasies 
in which we may play the role of the destroyer 
skipper stuffing mattresses in the shell holes 
and bringing his battered ship back to port, 
thereby winning the acclaim of the nation. Such 
imaginal activity is perfectly normal and some 
observers even believe it to be helpful occa- 
sionally in suggesting solutions to our problems. 
Fantasy becomes pathological only when the 
person begins to believe his fantasies and deny 
the real world. Then, fantasies become delu- 
sions. The misunderstood Napoleons in our in- 
sane asylums are people who live their lives in 
their private fantasy worlds. 
Commercialized fantasy is an interesting 
phenomenon in modern civilization. The movies, 
magazines and books-of-the-month are, for the 
most part, little more than standardized day 
dreams. Pay your money at the box office or at 
the rental library and you are afforded an hour 
or three of delightful escape from the humdrum 
realities of a frustrating life. 
Emotional exhaustion or neurasthenia.—A 
protracted emotional battle with frustration 
sometimes simply exhausts the individual. He 
develops a chronic fatigue, insomnia, restless- 
ness, irritability, a pervasive lack of enthu- 
siasm. This sort of reaction may, in extreme 
cases, develop into a complete physical and psy- 
chological collapse. It then becomes nervous 
breakdown. In the services it is one form of 
combat fatigue. 
Hysteroid reactions.—Prolonged emotional 
stress has definite effects upon the physiological 
workings of the body. The emotional factor 
in stomach ulcers is well-recognized. But the 
severely frustrated or conflictful individual may 
also develop symptoms that look medical in na- 
ture but for which the medical profession is un- 
able to prescribe. These symptoms are called 
functional or hysterical symptoms. The aviator 
with a mortal fear of flying may attempt to 
solve his problems by coming down with diar- 
rhea or severe stomach upsets while flying. The 
seaman may escape the fear of fighting by de- 
veloping a functional paralysis of a leg or a 
functional anesthesia of an arm or a functional 
blindness. Shell-shock patients often show such 
symptoms. To the individual the symptoms are 
real, but no bodily basis can be found for them. 
FRUSTRATION TOLERANCE 
In the process of growing up most of us 
learn that needs cannot all be satisfied immedi- 
ately. We learn to work before we achieve. We 
learn to deny ourselves today so we can enjoy 
ourselves tomorrow and next year. We learn, 
most of us, to delay gratification of our needs. 
And, with the inevitability of frustration in our 
complicated lives, this is a very handy lesson. 
Some people, however, never learn to tolerate 
frustration. The inability to delay gratification 
may be due to long practice at being a “spoiled 
brat.” Nobody really knows much about the 
genesis of this aspect of personality, but the 
theory that frustration tolerance is learned has 
a certain plausibility. The child who is not 
frustrated enough, whose every wish is grati- 
fied easily by very lenient parents, may go 
through life expecting the good things to fall 
into his lap if he is merely cute or pleasant. 
On the other hand, the child who is frustrated 
excessively may get more than a healthy 
amount of practice at adopting maladaptive re- 
sponses such as fantasy, aggression, repression, 
or regression. He, too, may be unable to sustain 
realistic effort in the face of frustration. 
Frustration tolerance is a pretty essential 
attribute for anyone who must absorb extensive 
training before he can assume the responsibili- 
ties and regards of an established position in 
life. The man who hopes to be an officer in the 
Navy, for example, who strongly wants the 
status, responsibility, and income of high rank, 
must tolerate a salutary frustration for quite 
a while. Not until long after his formal train- 
ing is completed will he really begin to gratify 
his needs. The “spoiled brat” would never be 
able to take it. 
SYMPTOMS AND CAUSES 
The doctor who treats the fever and ignores 
the virus, who cures the cough while the lungs 
disintegrate, will soon find himself without 
many patients. The psychiatrist who moralizes 
over the sins of his patients and clucks at their 
shortcomings will probably produce more neu- 
roses than he cures. And the ordinary human 
156 Chapter 8.— THE PSYCHOLOGY OF ADJUSTMENT 
being, priding himself on his common sense, 
who treats the symptoms of conflict and frus- 
tration while remaining insensitive to the 
causes, will hardly achieve the utmost as a 
handler of men. He will punish laziness and 
expect it to disappear. He will call aggressive 
behavior “meanness” and deal with it is if the 
aggressive person deliberately intends to be 
mean. He will diagnose regression as stupidity, 
fixation as stubbornness, escape as a “yellow 
streak.” He will attack these symptoms and 
sometimes he will succeed in making them dis- 
appear—temporarily. Sometimes his beating 
on the symptoms will seriously aggravate the 
disease behind his symptoms. Common sense 
diagnosis and common sense treatment of 
people’s behavior is not all it has been cracked 
up to be. 
Behavior is caused. Normal, everyday be- 
havior is caused. To understand normal be- 
havior, to control it, we must get beyond symp- 
toms and deal with the psychological factors 
producing the symptoms. The present treat- 
ment of conflict and frustration has been de- 
signed to help the leader see some of the dy- 
namics of behavior so that his understanding 
of it and his controlling of it will rise a little 
above the common sense level—the level of lazi- 
ness, stupidity, mulishness, and meanness. 
THE MEDICAL OFFICER'S RELATION 
TO PSYCHOPATHOLOGY 
Most of the reactions to conflict and frustra- 
tion are strictly normal phenomena. They 
occur every day and must be dealt with every 
day. Such reactions as neurasthenia and hys- 
teria are statistically rarer and, though they 
have normal counterparts, are generally re- 
garded as pathological. Extreme behavior in 
any of the nine directions we have talked about 
is classed as neurotic or psychotic. 
The medical officer should be able to recog- 
nize abnormal behavior when it occurs in his 
unit. Since the abnormal is almost always 
merely an extreme form of the normal, .the 
study of everyday behavior should aid in recog- 
nizing the serious departures from the every- 
day. 
The medical officer’s first job with respect to 
abnormal behavior is to recognize it and see 
that it receives treatment. 
The medical officer’s second job is to maintain 
an objective attitude toward mental illness. We 
have seen that behavior is caused. People do 
what they must do in any situation. The man 
who vomits at the thought of actual contact 
with the enemy, or the aviator who has dizzy 
spells during every flight should not be re- 
garded as a weak or cowardly or willful slacker. 
To regard them in such moralistic terms is to 
ignore the basic scientific point of view. Men 
with such symptoms are sick. They behave as 
they do because they must behave as they 
do. They need treatment if they are to be 
restored to usefulness. Only rarely, if ever, 
will accusations of “yellowness” be effective 
treatment. A vigorous “eating out” may re- 
move a symptom, but will not touch the cause of 
the symptom. If one symptom is “cured” an- 
other can be counted on to show up. 
To understand and control human behavior, 
either normal or abnormal, we need to deal 
with it on the level of causal dynamics rather 
than in terms of superficial common sense. 
THE READJUSTMENT OF MALADJUSTMENT 
Maladjustments come about as a result of 
conflict and the psychologically inadequate at- 
tempt to fulfill one’s needs. It should be em- 
phasized that such maladjustment or misad- 
justment is common in the lives of all of 
us, and we are often able to correct our mis- 
takes and bring about a satisfactory settlement 
of the problem that had earlier confused us. 
However, problems vary in complexity, and hu- 
mans vary in their skill at solving them. Con- 
sequently, physicians in general private prac- 
tice, naval flight surgeons, psychologists, psy- 
chiatrists, ministers, college deans, industrial 
personnel workers, and many others spend 
much of their time attempting to help people 
who are in trouble. 
Sometimes the help that is given is primarily 
environmental in nature. The physician recom- 
mends that the harassed business man take a 
month’s trip to Florida. The industrial per- 
sonnel worker arranges to have the worried 
worker transferred to another department 
where the foreman is more congenial. Or the 
flight surgeon has a talk with the jittery pilot’s 
skipper in an attempt to bring about more un- 
157 AVIATION MEDICINE PRACTICE 
derstanding. Such manipulation of the environ- 
ment may bring about temporary relief from 
the tensions of the moment and may even make 
it possible for the person needing help to work 
out a solution to his deeper problems. 
There are many cases, however, where en- 
vironmental therapy is of little promise, and 
correction of the maladjusted person’s own 
attitudes seems called for. Such treatment, 
though known by many other names, is most 
commonly referred to as psychotherapy or 
counseling. Since a large part of the flight 
surgeon’s services fall in this category, it seems 
worthwhile to discuss briefly some of the prob- 
lems involved. 
Because of the wide range of persons who 
have commonly been called upon for help of this 
sort, there have been many methods of treat- 
ment employed, some probably worse than no 
treatment at all. Even in the hands of those 
who would have liked to know better just what 
to do in each case, psychotherapy was for a 
long time an art that varied according to the 
personality of the psychotherapist. To a de- 
gree, this is still true. However, there are signs 
today of a science of psychotherapy arising to 
replace the art of the past. No longer is it 
claimed that psychotherapeutics is beyond the 
reach of investigative techniques. Today, the 
use of phonographic recordings of interviews, 
with subsequent analysis of the techniques in- 
volved, is a regular part of certain units in clini- 
cal research, and follow-up programs help to 
evaluate the methods used. 
It is impossible here to go into detail con- 
cerning accepted procedures. However, certain 
basic notions have evolved that should be men- 
tioned. Perhaps the most important principle 
that is generally recognized by those trained in 
this field is that to interfere in anyone’s life is 
a serious proposition, and that the wrong kind 
of counseling can be worse than none at all. 
Many old-fashioned approaches toward helping 
others are in ill favor and on their way out. 
For example, it is generally felt today that ex- 
hortation, sometimes with threats, is ineffec- 
tive, and that pledges and promises as a result 
of such exhortation cannot be expected to effect 
any deep-seated change. The dean of men who 
reprimanded the delinquent student, assured 
him that he could do better, threatened him 
with dismissal if he didn’t improve, and finally 
exacted from the student promises to do better, 
was probably wasting his time so far as any 
real help to the maladjusted student was con- 
cerned. His threats might conceivably have 
increased the student’s awareness of his own 
danger, but if the student was already under 
undue pressure and nervous tension an in- 
crease in his fears could hardly be of help. 
So it has come about that many ideas of 
counseling have been laid aside, and even the 
once widely accepted techniques of reassuring 
and encouraging are now recognized as often 
inducing a person to ignore his problems in- 
stead of facing them and solving them in 
wholesome fashion. In fact, the question has 
now arisen as to when a counselor or psycho- 
therapist should, if ever, attempt to solve a 
client’s problems for him. Even the time- 
honored phrase “If I were you” has come to be 
less and less used as the idea has grown up that 
“I” can never be “you”; neither can “I” ever 
completely “put myself in your place.” When 
the counselor tries to solve his client’s person- 
ality problems, we know now that he may be 
solving only his own. The psychotherapist may 
tell another person how his life should be lived, 
but what the client needs is to grow up emotion- 
ally to the point where he can live his own 
life without dependence upon anyone for such 
advice and guidance. Consequently, the giving 
of advice or the use of persuasion to induce 
behavior to the liking of the psychotherapist 
may succeed in bringing about the alleviation 
of symptoms, but will probably have no bene- 
ficial effect upon the causes of those symptoms. 
What is perhaps the opposite extreme in 
viewpoint has been presented as “nondirective” 
counseling. It is based on the following ideas 
expressed by Rogers: “Effective counseling con- 
sists of a definitely structured, permissive re- 
lationship which allows the client to gain an 
understanding of himself to a degree which 
enables him to take positive steps in the light 
of his new orientation. ... All techniques used 
should aim toward developing this free and 
permissive relationship, this understanding of 
himself in the counseling and other relation- 
ships, and this tendency toward positive, self- 
initiated action.” 
158 Chapter 8. —THE PSYCHOLOGY OF ADJUSTMENT 
Considering the type of problem and the 
intelligence of the subject that is most likely to 
be encountered by the flight surgeon, this ap- 
proach seems to hold great promise. In the 
majority of cases the flight surgeon is unlikely 
to have sufficient background and training to 
be justified in employing such techniques as 
hypnotherapy, narcosynthesis, psychoanalysis, 
or definitely directive methods of counseling, 
but proper use of the nondirective technique 
would be relatively safe, and might be expected 
to give definitely beneficial results, 
BIBLIOGRAPHY 
1. Barker, R. G., Kounin, J. S., and Wright, H. F., 
editors Child Behavior and Development. New York: 
McGraw-Hill Book Company, 1943. (Chapter 26.) 
2. Dollard, John, Doob, Leonard W., Miller, Neal 
E., Mowrer, O.H. and Sears, Robert R. Frustration 
and Aggression. New Haven: Yale University Press, 
1939. 
3. Heggen, Thomas, Mr. Roberts. Boston: Houghton 
Mifflin Company, 1946. 
4. Homey, Karen., The Neurotic Personality of Our 
Time. New York: W. W. Norton and Company, 1937. 
5. Hunt, J. McV. (editor) Personality and the Be- 
havior Disorders. New York: The Ronald Press Com- 
pany, 1944. (Volume I, chapter 14.) 
6. Maier, Norman, R. F., Psychology in Industry. 
Boston: Houghton Mifflin Company, 1946. 
7. Rogers, Carl R., Counseling and Psychotherapy. 
Boston: Houghton Mifflin Company, 1942. 
8. Ruch, Floyd L., Psychology and Life, 3rd Edition. 
New York: Scott, Foresman and Company, 1948. 
(Chapters 13, 14.) 
9. Shaffer, Laurance F., The Psychology of Adjust- 
ment. Boston: Houghton Mifflin Company, 1936. 
10. Snyder, William U., Present Status of Psycho- 
therapeutic Counseling. Psychological Bulletin, 1947, 
44(4), 297-386. 
159 CHAPTER 9 
NEUROPSYCHIATRY IN RELATION TO 
AVIATION MEDICINE * 
The subject of neuropsychiatry is hereby 
presented in what amounts to a brief outline 
of the course as given by the Department of 
Neuropsychiatry in the School of Aviation 
Medicine, U. S. Naval Air Station, Pensacola, 
Florida. A basic knowledge of psychiatry is as- 
sumed. Certain psychoanalytic concepts and 
the psychobiological point of view are related 
as they are applicable in the work of the naval 
flight surgeon. From the resident course of 40 
lectures and 20 seminars, selected subjects are 
presented here for the information of medical 
officers who are not themselves engaged in the 
practice of psychiatry. Resident students at 
the School of Aviation Medicine, in addition 
to the didactic work mentioned above, also re- 
ceive supervised clinical work on the wards of 
the U. S. Naval Hospital, Pensacola, Florida. 
In order to achieve brevity in this presenta- 
tion, liberal use is made of references, to which 
it must be assumed the medical officer will have 
access. 
LECTURE NO. 1 
Introduction to neuropsychiatry in aviation: 
1. Why study psychiatry? 
2. What is the psychiatric role of the Flight 
Surgeon ? 
3. Relation of psychology and psychiatry, 
4. Discussion of the course to be given. 
a. Reference and textbooks. 
b. Collateral reading. 
c. Seminars. 
d. Patients. 
e. Hospital clinics. 
f. Vocabulary. 
Since aviation medicine is a specialized form 
of industrial medicine, wherein personal rela- 
tionships, attitudes, and the effect of emotions 
on the individual are of primary importance, it 
is obviously necessary for the flight surgeon to 
be conversant with modern psychiatric thought. 
Personal, social and emotional problems are as 
great a cause of non-effectiveness in aviation 
as hernia, ulcer, or fever. Psychiatry is pre- 
sented as an intelligent approach to our every- 
day relationships with people, in that we deal 
with behavior, one’s relationship to his environ- 
ment, and to his fellow man. The neuropsychi- 
atric problem in the Navy is the responsibility 
of all medical officers; in aviation, it is the 
responsibility of the flight surgeon. 
It is not intended that a flight surgeon should 
be a qualified neuropsychiatrist nor psychiatri- 
cally conscious over all his other duties. Cer- 
tainly he should not pose as a specialist or at- 
tempt to psych his shipmates; but he should be 
psychologically minded and practice modern 
medicine for the benefit of his men. He should 
be able to comprehend the dynamic formulation 
of the doctor-patient relationship, should be 
familiar with normal personality development, 
the meaning of psychoneurosis, the common 
manifestations of psycho-pathology, the effect 
of emotions in altering physiology, and the 
more simple methods of treating emotional dis- 
orders. Psychology is presented as the working 
of the normal mind, the inter-relation between 
organism and environment; whereas psychiatry 
places emphasis on the mind that has failed to 
establish harmonious adjustment, or where this 
adjustment has been disrupted in the inter-re- 
lation between organism and environment. 
* Prepared by LCdr Philip B. Phillips, MC, USN. 
160 Chapter 9. — NEUROPSYCHIATRY IN RELATION TO AVIATION MEDICINE 
Psychiatry is no longer primarily interested 
in the end products, but its emphasis has 
shifted from an interest in what to why. Em- 
phasis is placed on the concept that the term 
“normal” includes a wide range of reactions, 
depending on the individual and environment. 
Normalcy referring to mental health exists only 
when the efficiency, the physical and emotional 
wellbeing, the social behavior, and/or the in- 
dividual’s thinking remain within the socially 
accepted limits of a specific situation. 
Emphasis is placed on the body-mind rela- 
tionship and the necessity of dealing with men- 
tal and emotional problems both from the psy- 
chological and the organic viewpoint. The flight 
surgeon is concerned with two cardinal factors: 
the personality of the individual and the en- 
vironment in which that individual finds him- 
self. 
References :* 
(E)—pages 53-146. 
(P)—pages 9-13. 
(S)—chapter I. 
LECTURE NO. 2 
Development of the mind and personality: 
1. Psychosomatic relationships. 
a. The influence of the mind on body 
functions, and vice versa, 
2. The origin of the mind. 
a. The levels of the psyche: 
(1) Tropism. 
(2) Reflex. 
(3) Instinct. 
(4) Intelligence. 
3. Influence of environment on personality 
(body—mind). 
4. Requirements for an organism to func- 
tion at the level of intelligence. 
5. Fields of concern regarding relationship 
to one’s environment. 
6. A balanced personality. 
7. The four-square man. 
The constant influence of the psyche on the 
soma and vice versa is pointed out. In fear, 
the physical accompaniments of tachycardia, 
dry mouth, dyspnea, and often nausea and ver- 
tigo occur. The reverse is also true, for if one 
suddenly experiences one of the latter symptoms, 
apprehension or fear is the result. Thus it is 
held that the body-mind relationship is a con- 
stant and dynamic one. 
Apparently the mind has developed in order 
that the organism may be able to solve the in- 
creasingly complex problems faced and survive. 
The four levels of the psyche are: (a) the level 
of tropism, where behavior is governed chiefly 
by physical and chemical laws; (b) the level 
of reflex, where a constant stimulus gives a 
constant response, illustrated by the actions of 
an earthworm touched by an electrode; (c) the 
level of instinct, which is a series of reflex ac- 
tions, fixed, stereotyped and inelastic, but which 
may become complex; and (d) the level of in- 
telligence. Here stimuli are received by the 
cerebral cortex and selectively distributed, and 
the response and behavior follows no fixed pat- 
tern. 
Another dynamic relationship exists between 
the individual and the environment, and illus- 
trations may be readily brought to mind demon- 
strating the variation of behavior under vary- 
ing environmental conditions. 
The requirements for an organism to func- 
tion at the level of intelligence are: (a) the 
ability to form abstractions logically and cor- 
rectly; (b) the ability to comprehend what 
others understand and explain; (c) the ability 
to combine information logically and correctly; 
(d) the ability to so act as to obtain the desired 
goal. 
The cardinal fields of concern regarding the 
relationship to one’s environment are: (a) feel- 
ing; (b) thinking; (c) acting. 
A balanced personality has been compared 
to a four-legged chair, the legs being love, work, 
play, and worship. Any leg out of proportion or 
missing results in an unbalanced personality. 
The four-square man is an illustration given 
by Cleeton and Mason in their book, “Execu- 
tive Ability”, wherein they state that the “area” 
of a man’s success is determined by the square 
enclosed by the four sides: (a) ability (men- 
tal) ; (r) reliability (spiritual) ; (e) endurance 
(physical) ; and (a) action (integration of all 
factors). 
References: 
(D)—pages 17-33. 
(J) —pages 11-17. 
(K) —pages 3-18. 
(S) —pages 6-10. 
(T) —pages 1-8. 
* All references and seminars referred to by numbers in paren 
theses will be found on pages 186-188. 
161 AVIATION MEDICINE PRACTICE 
LECTURE NO. 3 
The structure of the personality: 
1. Instincts: 
a. Where they exist (the Id). 
b. The pleasure principle. 
c. Aim and object of the instincts. 
2. Need for new personality factor to con- 
tact reality and adapt to its demands: 
a. Origin of the ego. 
b. Its function, 
c. The reality principle. 
3. Need for permanent retention of certain 
demands and ideas of reality: 
a. The super ego: 
1. Its origin and role. 
2. Manner of acting. 
3. Ego-ideal. 
Instincts are held to exist in the portion of 
the personality known as the Id. They follow 
the pleasure-pain principle: that tendency of 
instincts to seek release of tension and avoid 
the pain of tension. They have no regard for 
morals, codes, or persons, and disregard logic, 
time and comfort of others. Their aim is to 
dissipate the charge of energy which is produc- 
ing tension, and their object is some thing or 
person in the world contact which will fulfill 
the aim of instincts as an avenue of release 
for tension. Undisciplined instinct gratification 
cannot last; the growing child must be made 
aware that some control of expression of desire 
must be brought about to adapt to social life. 
A new factor of the personality develops for 
the purpose of contacting reality and adapting 
to its demands. 
This ego part of the personality arises from 
the Id and is developed to act as mediator be- 
tween two forces, the forces of the instincts 
and the forces of reality. The reality principle 
is the capacity of the organism to forego im- 
mediate pleasure in order to insure pleasure 
and avoid pain in the future. 
A third portion of the personality, the super 
ego, develops for the permanent retention of 
certain demands and ideas of reality. Repeated 
parental prohibition gradually is incorporated 
into this portion of the personality, the super 
ego. It affects the ego by making it feel fear, 
shame, disgust, etc., indicating unacceptable Id 
desires have been stimulated. Parental limita- 
tion and imitation both are included in the 
super ego, which besides its punitive role also 
includes the ego ideal, so that the super ego 
embraces both necessary social prohibitions and 
higher cultural strivings. 
Recapitulating, it is held analytically that 
there are three parts to the personality. The 
driving forces of the instincts exerting them- 
selves through body and mind, demanding love 
and comfort, make up the Id. Being dependent 
upon others for this love and comfort, a part 
of the psyche differentiates itself, taking cog- 
nizance of the environment, and begins to hold 
the instincts to what the environment will toler- 
ate in the way of satisfying instinct tensions. 
This is called the ego. To save excessive anxiety 
with each new danger, a third part of the 
psyche is differentiated, which automatically 
makes decisions and controls behavior. This is 
the super ego. 
References: 
(A)—pages 21-34. 
(D)—pages 29-68. 
(H)—pages 80-125; 294-342. 
(K)—pages 26-29; 35. 
LECTURE NO. 4 
The psychosexual development of the child: 
1. Environmental adaptation problems: 
a. Genitalization of the libido. 
b. Finding external object. 
c. Redirection of excess energy. 
2. Genitalization of the libido; 
a. The physical body and its constituents 
(psychologically) : 
(1) Organs of metabolism. 
(2) Organs of internal integration. 
(3) Organs of external integration, 
b. The intellectual capacity. 
c. Instincts. 
d. Erotogenetic zones. 
e. Pleasure-pain principle. 
f. Repetition compulsion. 
Ages in the normal psychosexual develop- 
ment to maturity: 
Oral 0 - li/2 
Anal 11/2- 3 
Genital 3-6 
Latency 6 -12 
Pubertal or adolescent 13 -on 
1. Homosexual 13 -15 
2. Heterosexual 16 -? 
162 Chapter 9. — NEUROPSYCHIATRY IN RELATION TO AVIATION MEDICINE 
DIAGRAM OF DEVELOPMENTAL STAGES 
(The Theoretically Normal Development.) 
A. Libidinal Localization 
B. Aim, or Mode of 
(erotogentic zones). 
Pleasure-Finding. 
C. 
Libidinal Object-Finding. 
INFANCY PERIOD 
Pregential Period 
Infantile sexuality 
Auto- 
Narcism 
Alio- 
erotism* 
’erotism 
1. Oral stage: 
a. early oral 
Sucking, swallowing 
at 
first 
Oral 
(incorporating) * * 
object- 
less 
object- 
choice 
b. late oral 
Biting, devouring 
(destroying, annihilating) 
Primary 
Narcism 
Oral- 
sadistic 
object- 
choice 
2. Anal stage: 
a. early anal 
Expelling / looking 
(rejecting) 1 exhibiting 
(destroying)! handling 
< inflicting 
Retaining J pain 
(controlling)! submitting 
Anal and 
anal- 
sadistic 
object- 
choice 
Early genital period: 
(possessing) \ to pain 
(phallic stage) 
Touching, rubbing, exhibit- 
ing and looking at geni- 
talia investigating, com- 
paring, questioning, phan- 
tasying (tender affection) 
Parent 
object- 
choice 
Oedipus- 
phantasies 
LATENCY PERIOD 
No new zone 
Repression 
Further 
Dimin- 
Develop- 
Reaction-formation 
decline 
ished 
ment of 
Sublimation 
of 
auto- 
Narcism 
social 
Affectional trends 
erotism 
feelings 
ADOLESCENT OR PUBERTAL 
PERIOD 
Late Genital Period 
Reactivation of modes or 
Revival 
Fresh 
Revival of 
Revival of zone sen- 
aims of infancy period 
of 
auto- 
wave of 
Oedipus 
sitivity of infancy 
erotism 
Narcism 
object choice 
period 
Later, functioning of 
Emergence of adult mode of 
Homosex- 
vaginal zone 
pleasure-finding 
> 
f 
ual object- 
choice 
Heterosex- 
ual object- 
choice 
* Not synonymous with masturbation. 
** The words enclosed in parentheses refer to Ego attitudes 
and trends arising on the basis of Id impulses. 
163 AVIATION MEDICINE PRACTICE 
3. Polyvalent 16 -21 
4. Monovalent 21 - 
Maturity 21 - 
In making a satisfactory adaptation to the 
environment, the young human being faces 
problems involving localization of pleasure-giv- 
ing zones to areas useful to the adult and race, 
finding an object external to the individual 
through whom the function of reproduction 
may be carried out, and redirecting the excess 
energy away from the primary function of re- 
production and making it available for other 
purposes in the struggle for existence. 
References: 
(J) —pages 18-51. 
(K) —pages 20-29. 
(P)—pages 15-307. 
(H)—page 110. 
LECTURE NO. 5 
The oral and anal stages: 
Oral stage: 
1. Stimuli on newborn child: 
a. External. 
b. Internal. 
2. Response to stimuli. 
3. Learning of first year: 
a. Gratification by sucking. 
b. Gratification by biting and chewing. 
4. Psychological requirements of this period. 
Anal sadistic: 
1. Factors involved. 
2. Relationship to mother. 
3. Development of super ego. 
4. Important behavior concepts established. 
5. Concept of ambivalence. 
At birth, the child is exposed to two groups 
of stimuli which cause discomfort, inducing 
him to use his energy in their removal to regain 
a tensionless state. External stimuli include 
cold, light, loud noises, changes in skin humid- 
ity, etc.; while internal tensions are those aris- 
ing from his inner physiological needs. Arousal 
of instinct causes a production of energy which 
seeks an outlet; if there is no outlet the indivi- 
dual feels fear, directly proportional to the un- 
expended energy; whereas fear is lessened by 
an effort to expend the energy. 
Through this process the ego becomes aware 
of one of the salient principles of life: discom- 
fort or danger will cause fear unless the indivi- 
dual directs his bodily energy toward removing 
the cause or himself from the vicinity. The 
oral stage of development is touched on briefly, 
constituent parts pointed out, and the necessity 
that this stage be traversed without the child 
being too frequently unsatisfied or too abund- 
antly treated. Anal-sadistic stage is described 
as the stage of infancy wherein bowel and blad- 
der control is being gained and the child ex- 
periences the variable feelings of the parents 
regarding his excretory activities. He must 
learn to control some of his instinctive pleas- 
ures to meet the demands of the mother. 
The process of toilet training lays the basis 
for certain important behavior concepts to 
come later: (a) to please the loved one, we 
must give to the loved one, relinquishing pos- 
sessions we would like to retain. He may take 
over a hostile mother’s attitude of dislike and 
repudiation of the value of his gift and come 
to consider it worthless or contemptible. He 
learns gifts can be given to express derision and 
antagonism; that is, he can retaliate to the 
mother by giving his gift in inappropriate 
places. The child may develop a feeling he is 
more powerful than the mother, and that he 
can master her by anal activities. 
The instinct of aggression thus becomes con- 
nected with anal functions. The child is now 
faced with opposing feelings in that he can 
love and hate the same person at the same 
time. He may become ambivalent. For his 
future development it is important these con- 
flicting feelings and opposing activities be syn- 
thesized and that the ambivalence be replaced 
by true object love unmixed with hate; that 
part of the hate be changed to aggressive ac- 
tivity toward the love object in order to possess 
and master, part be changed to aggressive ac- 
tivity tempered with sympathy and understand- 
ing toward other human beings, and part be 
changed to aggressive action against the dan- 
gers and difficulties of the physical world. The 
method of toilet training has farther-reaching 
consequences than the attainment of cleanliness, 
because so many important ideas are connected 
with it in the child’s mind; therefore the meth- 
ods used by the parents are important in the 
formulation of his super ego and ego reaction 
pattern. 
164 Chapter 9. — NEUROPSYCHIATRY IN RELATION TO AVIATION MEDICINE 
References: 
(H)—pages 168-189. 
(J) —pages 21-35. 
(K) —pages 21-25. 
(P)—pages 15-70. 
LECTURE NO. 6 
The genital, latent, and adolescent stages: 
1. Displacement to genitals. 
2. Oedipus complex (parental rivalry). 
3. Latent period. 
4. Adolescence. 
The importance of the genital stage of psy- 
chosexual development during the pre-school 
years, and its effect upon later personality for- 
mation, are discussed. In this the oedipus con- 
flict is described in essence as a libidinal striv- 
ing taking the form of unconscious desire for 
sexual satisfaction with the parent of the op- 
posite sex. 
The latent period, the period of beginning 
educability, with the repression of desire for 
the parent of the opposite sex and the sublima- 
tion of aggressive impulses toward the father 
being the psychological basis for combative 
games with playmates in the boy and this 
same process in the girl manifesting itself with 
playing house, with dolls, etc., continues the 
normal development of the individual. Two new 
situations confront the child, dealing with the 
school and teacher, an authoritarian father 
figure, and with playmates and other children. 
His reactions will depend largely on how his 
relations with his parents were, and upon what 
modes of behavior he adopted in dealing with 
them. 
The stage of adolescence, beginning with the 
prepubertal period and encompassing the 
marked expansion of the sexual instincts, is 
discussed both from the normal and the patho- 
logical view. The possible retreat of the libido 
from genitalization to earlier stages in the face 
of a strict Super Ego is pointed out, as are the 
difficulties which develop from inadequate early 
genitalization, wherein the child becomes self- 
centered, seclusive, lacks interest in the outside 
world, etc. The ego’s mechanism of relieving 
Id tensions through allowing direct expression, 
towards objects permissible to the Super Ego, 
and by changing the mode of expression, is dis- 
cussed. The adolescent anxiety resulting from 
attempts to close all outlets to particular im- 
pulses is related to earlier feelings of anxiety. 
The development of reaction formation where- 
by Id impulses are expressed in behavior ex- 
actly opposite to their direct expression is also 
discussed. 
References: 
(J) —pages 44-51. 
(K) —pages 25-26. 
(P)—pages 71-307. 
(R)—pages 74-118. 
LECTURE NO. 7 
The unconscious, pre-conscious, and the con- 
scious : 
Unconscious: 
1. Definition. 
2. Main attributes of unconscious (Freud). 
3. Jung’s views. 
4. The content. 
5. Reason for a belief in a dynamic un- 
conscious. 
6. Chief advantages from accepting the 
dynamic concept. 
Pre-conscious; 
1. Definition. 
Conscious; 
1. Definition. 
2. Content. 
3. Dissociation of consciousness: 
a. Normal. 
b. Abnormal. 
The unconscious is that vast quantity of 
mental life which either never was in con- 
sciousness or, previously in consciousness, has 
been repressed. The elements are active con- 
stituents of mental life. The somatic and emo- 
tional effects are more powerful than those 
emanating from consciousness. It is dynamic 
and capable of affecting conscious ideational or 
emotional life without the individual’s being 
aware of this influence. Jung sees the uncon- 
scious as consisting of both a personal un- 
conscious and a collective or racial unconscious. 
The unconcious contains mental processes en- 
tirely beyond the realm of voluntary recall. It 
is the reservoir of past experiences of the in- 
dividual, having begun shortly after birth of 
the person and continuing to grow with him. 
Reasons for believing in a dynamic uncon- 
scious are: the post-hypnotic carrying out of 
suggestions held in the unconscious; the evi- 
165 AVIATION MEDICINE PRACTICE 
dences found through discovering the latent 
meaning1 of dreams; the discoverable bases 
for common slips or errors of speech, memory, 
and action; the small amount in consciousness 
at any one time in comparison to the latent 
content of the mind. 
The advantages to be derived from accept- 
ance of this concept are: an understanding of 
what the individual may be trying to express 
by his behavior; an understanding of the 
causes of various forms of behavior; and un- 
derstanding that the difference between the 
normal and abnormal mental processes is quan- 
titative in nature, and an understanding of the 
forms of psychotherapy which may advantage- 
ously be employed in a given case. 
The pre-conscious is defined as that part of 
mental life which in appropriate circumstances, 
either through an effort of the will or stimu- 
lated by an associated idea, can be brought up 
into consciousness. 
Consciousness is that part of mental life 
proportionately infinitesimal of which the in- 
dividual is aware at any given time. It repre- 
sents the upper stratum of life. It developed 
later to meet the demands of adaptation to the 
external, real world. It includes only those 
mental processes concerning which there is 
awareness at a given moment. Normally, con- 
sciousness is an invisible whole or stream of 
thought toward a given end. It can be broken 
up into independent fragments not coordinated 
to common ends. This is called dissociation of 
consciousness. This may be normal when it 
is temporary, partial in nature, and under the 
control of the individual, to be abandoned at 
will. It is abnormal when these latter criteria 
are not met. 
The Id is entirely unconscious, the ego is 
largely unconscious but includes pre-conscious- 
ness and consciousness, the super ego includes 
consciousness, the pre-conscious, and a large 
portion of unconscious material, and has direct 
access to the Id. The ego constitutes the greater 
portion of the personality’s contact with the 
outer world, although the super ego participates 
in this. 
References: 
(D)—pages 35-39. 
(H)—pages 22-57. 
LECTURE NO. 8 
The fundamental problem of life: 
1. Fundamental problem—adjustment to the 
environment. 
2. Goal of behavior—peace of mind. 
3. Peace of mind: 
a. Happiness. 
b. Love. 
c. Self-esteem. 
4. Personality-Environmental struggle: 
a. Three fundamental urges: 
(1) Self preservation. 
(2) Race preservation. 
(3) Communal preservation, 
5. Factors bearing on Personality-Environ- 
mental struggle: 
a. Constitutional. 
b. Developmental environment. 
c. Precipitating: 
(1) Emotional deprivations. 
(2) Threatened insecurity. 
(3) Physical or physiological causes. 
6. Introduction of conflict. 
The fundamental problem of life which all 
individuals face is that of adjusting to the 
environment. The environment includes more 
than the physical surroundings, for it involves 
all those things which go to make up a person’s 
life situation. It is through solution of this 
fundamental problem that the individual seeks 
to attain the goal of all behavior, which is 
peace of mind. 
Peace of mind has three constituent parts: 
happiness, in which there must be an element 
of hope; love, wherein the individual must feel 
security, that he is wanted, cared for and will 
be protected; and self-esteem, wherein he must 
feel no persistent doubts regarding his own 
capabilities. The individual who solves his 
problems so as to attain these three com- 
ponents attains the primary goal, peace of 
mind, and would be considered well adjusted 
to his environment. 
In the personality-environmental struggle, 
the three fundamental urges are as given. Of 
the factors bearing on this personality-environ- 
mental struggle, the constitutional factors are 
probably less important than the developmental- 
evironmental factor. In the latter, the good 
or bad results of emotional relationships, train- 
166 Chapter 9. — NEUROPSYCHIATRY IN RELATION TO AVIATION MEDICINE 
ing, and education predispose to good or poor 
capacity for adjustment. Freud has said that 
a child who is loved by his mother until he is 
5 cannot help but be a success. The child’s 
attitude toward men and women is conditioned 
by his early attitudes towards his parents. The 
details of his early developmental period are 
important in the diagnosis, prognosis, and 
treatment of possible later difficulties. 
In this early period, he learns to be trust- 
worthy or deceptive, to love or to hate, to be 
dependent or independent, lazy or industrious, 
uncomfortable or at ease with people. The 
precipitating factor is seldom the real cause 
of the mental reaction. The margin of toler- 
ance varies markedly with different individuals. 
In the functional mental illnesses the causes are 
often internal stresses brought to light in the 
form of symptoms. These come from emotional 
deprivation, parental rejection, lack of approval, 
recognition, parental love, ego gratification, etc. 
There may be threatened insecurity in new 
situations, changes of jobs, moves, promotions; 
and there may be physical or physiological 
causes such as exhaustion, exposure, injury, 
systemic diseases, etc. These factors introduce 
a situation called conflict in the personality 
versus the environment struggle. This includes 
the conscious and the unconscious wants, vs. 
what the individual can have or can get. Frus- 
tration of instincts and difficult conformation 
to herd tendencies are particularly frequent in 
military environment. Many conscious conflicts 
are solved readily every day, though the deci- 
sions are often made on a basis unconscious to 
the person. 
References ; 
(K)—pages 30-39. 
(d) —pages 13-40. 
(S)—pages 16-21. 
(U)—pages 13-16. 
LECTURE NO. 9 
The solution of conflict: 
Unconscious conflicts: 
1. Ambivalence. 
2. Direct compensation, 
3. Around sex. 
Cultural conflict: 
Chief sources of internal stress in military 
environment: 
1. Emotional deprivation. 
2. Threatened insecurity. 
3. Physical burdens. 
The solution of conflict: 
1. Definition of complex: 
a. Conscious or unconscious. 
b. Emotional, not logical thinking. 
c. Psychic energy involved. 
d. Emotional tone troublesome and re- 
pressed. 
e. Disproportion between stimulus and 
reaction. 
Mental anguish: 
1. Tension. 
2. Deprivation or frustration—results in 
aggression. 
Mental mechanisms: 
Complexes: 
1. Good and bad. 
Conflicts may be conscious or unconscious, 
and there may be a conflict between conscious 
desires and other unconscious, incompatible de- 
sires; between reality, ideals, morals, etc. Am- 
bivalence is often a factor. There may be 
a discrepancy between one’s ideal picture of 
oneself and one’s own past deeds. These con- 
flicts may affect one’s behavior. Certain cul- 
tural conflicts exist between inconsistent or 
conflicting trends. Among these are man’s 
attitude towards women, towards women doc- 
tors, towards a wife’s career, towards killing, 
towards sex, etc. Strong, flexible characters can 
and do adjust; the weaker ones are apt to 
crack under the strain. 
In a military environment, some of the chief 
sources of internal stress are separation from 
home, new occupations, increased responsibili- 
ties, physical fatigue and exposure, the imper- 
sonality of the environment, regimentation, loss 
of personal liberties, accountability for be- 
havior, and anticipation of injury or death. 
These all fall under either emotional depriva- 
tion, threatened insecurity, or physical bur- 
dens. A conflict involves persistent, automatic 
attempts at solution. The psychic energy asso- 
ciated with a desire for gratification, threat 
to self-esteem or fear of injury, when denied 
an outlet, results in mental anguish, exaggerat- 
ing the demand for solution. 
Complex is defined as a group of related ideas 
vivified by strong emotional tone and demand- 
ing expression in consciousness. The action is 
167 AVIATION MEDICINE PRACTICE 
related to the amount and kind of emotion 
present, and these complexes may be manifest 
by character traits, slips of the tongue, man- 
nerisms, and forgetfulness. They may be con- 
scious or unconscious; they involve emotional 
rather than logical thinking; there is usually 
a marked disproportion between the stimulus 
and the reaction. 
When a biological threat or danger faces the 
organism, tension results, and the autonomic 
nervous system responds either with a fight or 
a flight reaction. Tension is always present 
in a waking state and is manifest as tonus, 
or the ability or readiness to react. A psycho- 
logically sick person shows tension out of pro- 
portion to the apparent problems facing him. 
His problem, however, may be unconscious to 
him. Chronic tension wears one out somatically. 
With deprivation or frustration, either par- 
tial or complete, aggression results. This may 
be direct, against the frustrator, or indirect, 
against a symbol. With the aggression, there 
is accompanying fear and anxiety. To rid him- 
self of the mental anguish and in response to 
its dynamic urges, he attempts to solve the 
conflict. The mental procedures or processes 
employed in this solution are called mechan- 
isms. As the goal is peace of mind, these 
mechanisms may be thought of as a procedure 
by which the individual strives to adjust to his 
environment. 
Complexes may be either good or bad. The 
former accomplish something useful and are 
associated with such things as patriotism, fami- 
ly honor, politics, religion, and hobbies. Bad 
complexes are ones which have a destructive 
effect on the individual or environment. 
References: 
(K)—pages 122-151. 
LECTURE NO. 10 
Mental mechanisms: 
1. Definition and purpose. 
2. Types; 
a. Daydreaming (fantasy). 
b. Rationalization. 
c. Compensation. 
d. Sublimation. 
e. Projection. 
f. Identification (introjection). 
g. Displacement. 
By mental mechanisms is meant the habitual 
manner in which an individual works out his 
problems, what he does when confronted with 
difficulties and mistakes. Mental mechanisms 
not only shape the functional symptoms but 
disguise their real purpose. Through mental 
mechanisms the individual rids himself of un- 
pleasant emotional tone or mental pain arising 
from the dynamic urges of the conflict. The ob- 
ject of solution is to obtain peace of mind. 
Mental mechanisms may be thought of as 
means of striving to adjust to the environment. 
“ . . . abnormal mental mechanisms differ 
in kind very little or not at all from the normal. 
The same mental processes are observed in the 
socially well-adapted person as in the malad- 
justed psychoneurotic. It is considerably more 
a matter of degree.” 
Among the types of mental mechanisms em- 
ployed in the solution of conflict are: 
1. Daydreaming or fantasy formation. 
2. Rationalization, or the necessity for find- 
ing a reason or explanation for every pheno- 
menon, This has been called self-deception 
through adventitious reasoning. 
3. Compensation, an attempt to make up for 
real or fancied deficiencies by appropriate al- 
terations of thought or behavior (this may be 
conscious and deliberate as well as unconscious 
and automatic). 
4. Sublimation, a mechanism by which en- 
ergy from undesirable or unattainable ideas or 
desires is drafted off into a channel which is 
thought not undesirable or unattainable, or a 
redirection of energy. 
5. Projection, wherein one condemns in 
others faults to the commission of which one 
himself has a conscious inclination; seeing one’s 
own faults in others without recognizing them 
to be our faults. 
6. Identification, whereby the individual 
identifies himself with another individual, real 
or imaginary, in order that he may derive 
strength from the other individual to help 
him attain certain unconscious desires. Award- 
ing ourselves someone else’s virtues. 
7. Displacement, wherein the emotion aris- 
ing through conflict is transferred to another 
person or object by substitution. 
168 Chapter 9. — NEUROPSYCHIATRY IN RELATION TO AVIATION MEDICINE 
References: 
(D)—pages 42-68. 
(S) —chapter 5. 
(T) —pages 91-100. 
(V)—page 705. 
LECTURE NO. 11 
Psychiobiology and 'psychobiological constitu- 
tional and reaction types: 
1. Origin of the concept of psychobiology: 
a. Definition. 
b. Subject matter. 
2. Comparison with other schools: 
a. Freud. 
b. Adler. 
c. Jung. 
d. Behaviorist. 
e. Gestalt. 
The concept of psychobiology was introduced 
by Adolph Meyer and regards the individual 
as a whole or functioning unit, any part of 
which may break down and influence the func- 
tions of the total individual. It views the in- 
dividual in the long section of life, taking into 
account all important life happenings, somatic 
and emotional. It is the science of personality 
function. According to Meyer, it is the science 
of understanding how and why the integrated 
unit or person made up of organs and parts 
works together, not in the sense of a mere 
summation of parts and part functions, but as 
an integrate in inter-relationship, to produce 
what we call a live man, capable of living, grow- 
ing, reproducing, acting, talking, feeling, un 
derstanding, remembering, anticipating, hav- 
ing desires, ambitions, special appetites and 
traits, which single him or her out as a par- 
ticular one of the zoological entities specified 
by the term man. 
Psychobiology deals with the meanings of 
things in the life of a person. It notes the 
occurrences of the life history and makes an 
estimate of their significance in producing a 
psychoneurotic or psychotic maladjustment. 
Freud reached the conclusion catharsis was 
sufficient. Free association developed into 
psychoanalysis. He felt psychic phenomena 
were uniformly present, determined by the in- 
dividual’s mental motives, even though out of 
awareness. He postulated the unconscious by 
reason of his findings in free association, mis- 
takes, and dreams. He also introduced the 
concept of repressed infantile sexuality. 
Adler postulated organ inferiority, and de- 
veloped the idea that most emotional disorders 
grow out of a striving for power, indulged 
in an effort to compensate for feelings of in- 
adequacy and inferiority. He felt neuroses were 
all on a basis of inability to meet goals, a 
face-saving dodging of social responsibility. 
Jung introduced analytic psychology and the 
concepts of the personal and collective or racial 
unconscious. He felt neurosis was a failure 
in an attempt at adjustment to life, and that 
symptoms resulted because not all of the nat- 
urally adaptable materials were used. He laid 
the groundwork for the ideas of Introvert and 
Extrovert. 
The Behaviorist School of Pavlov and others 
was wholly objective, threw heredity to the 
winds, developed a stimulus-response psychol- 
ogy, disallowed the subconscious. 
The Gestalt School dealt with configuration 
and contrasted the meaning of an idea with 
its structure and content. It advanced the con- 
cept of the human brain as an energy system 
possessing the power of will, and held that 
the whole is not built by coordination of parts, 
but that parts are derived by differentiation 
or individuations from the whole. 
Psychobiological constitution and reaction 
types is a study of the relationship between 
human form and human nature. Sheldon’s 
classification of endomorph, mesomorph, and 
ectomorph is undoubtedly familiar to readers. 
Kretschmer’s classification of the pyknic, 
asthenic, athletic, and dysplastic physiques is 
also well known. Sheldon classified tempera- 
ment as viscerotonic, somatotonic, or cerebro- 
tonic. These classifications may be related in 
that asthenic or ectomorph is by personality 
more often schizoid, introvert, and cerebro- 
tonic, and tends towards anxiety or schizo- 
phrenia if mental illness develops; whereas the 
phynic or endomorph, cycloid, extrovert, vis- 
cerotonic tends toward hysteria and manic de- 
pressive disease if mental illness develops. 
References: 
(D)—pages 69-93. 
(S) —pages 29-32. 
(T) —pages 9-25. 
(X)—pages 4-48. 
169 AVIATION MEDICINE PRACTICE 
LECTURE NO. 12 
Broken personalities: 
1. Somatic type (physical illness person- 
alities) : 
a. Physically crippled personality. 
b. Illness-prone personalities. 
c. Diseases with first symptoms physi- 
cal; later, disorders of perception, 
thinking, feeling, behavior. 
2. Hypophrenic (stupid) personalities. 
3. Isolation type (lonely) personalities. 
4. The schizoid type—queer personalities. 
5. The cycloid type (moody personalities). 
6. The neurotic type (frustrated person- 
alities) . 
7. The anti-social type (perverse person- 
alities). 
The core of the human personality is con- 
stitutional, and largely genetically determined. 
This can be influenced environmentally, and 
life’s experiences may be thought of as build- 
ing stones which go into the construction of 
the completed personality. Building is never 
finished, however, since this is a dynamic pro- 
cess continuing unto death. The degree of 
mental health depends both on the constitu- 
tional core and the way life’s experiences 
are built into the structure. 
In our dealing with people as adults we are 
prone to categorize individuals into certain 
type of personality. Menninger, in his text 
“The Human Mind,” has given a practical and 
descriptive outline of the personality types 
which are prone to have unusual difficulties 
under adaptational strain. It is important that 
the Flight Surgeon recognize these various 
types of personality. Menninger, in his text 
deal appropriately with each type as he serves 
his group. 
First is the somatic type, or physical illness 
personality, who gives somatic evidence of his 
psychological difficulties. Various sub-types are 
recognized, including those prone to asthma, 
constipation, peptic ulcer, hypertension, etc. A 
second type which will have difficulties in adap- 
tation is the hypophrenic, or stupid personality. 
These individuals of limited intellectual capacity 
can succeed only under favorable conditions. 
They frequently get caught for crimes smarter 
people get away with; they are prone to follow 
simple, though tedious, tasks. 
Ninety percent of these people are peaceful, 
law-abiding citizens. A third type, the isola- 
tion, or lonely personality, is marked by seclu- 
siveness, eccentricity, unsociability. Some of 
these are the temperamentally unsocial who 
prefer to be left out of things; and others are 
the wistful outsiders who long to enter social 
activities and either don’t know how or are 
held back by fears. These people rate particu- 
lar attention from the flight surgeon. A fourth 
type, the schizoid or queer personalities, show 
a common tendency, their inability to get along 
well with other people. 
By sub-types, they may be the seclusive, the 
hardboiled, the artistic, the grouchy, or the 
radical. Their adaptation is particularly diffi- 
cult. A fifth type, the cycloid or moody per- 
sonalities, are those who show mood swings 
not provoked by the environment. In the up 
phase, they do a prodigious amount of work, 
are full of pep, and often participate in fistic 
or legal fights from encountering unsuspecting 
irritants about them. In the down phase, they 
show no interest, no enthusiasm, are apathetic, 
self-deprecatory, are in need of help. 
Another type, the neurotic, or frustrated 
personalities, are those whose childhood devel- 
opment was such that the conflicts between 
their instinctive tendencies and the environ- 
ment were never resolved in a way wholly 
satisfactory to the ego, and who are therefore 
constantly impelled to indulge in behavior 
which gives them a needed satisfaction at an 
exorbitant cost. 
This type always contrives to defeat its own 
aim, to spike its own guns, and lay its own 
pitfalls. Their primitive sexual and aggressive 
instincts have been modified to meet social 
requirements only with painful difficulty. In- 
decisiveness is marked. They substitute neu- 
rotic symptoms for instinctual gratification. 
Another type, the antisocial or perverse person- 
alities, are those often called psychopathic 
personalities. Perverse is a good word. These 
people play at the game but break’the rules. 
Their defectiveness is in their emotional and 
volitional functions; they cannot keep out of 
trouble. Rather than symptoms, they show be- 
havior abnormalities, and the environment suf- 
170 Chapter 9. — NEUROPSYCHIATRY IN RELATION TO AVIATION MEDICINE 
fers. They may be troublesome, even danger- 
ous; yet they themselves suffer worst of all. 
They have no place in naval aviation. 
References: 
(A)—pages 34-158. 
LECTURE NO. 13 
Psychosomatic relationships: 
1. Definition of psychosomatics. 
2. Effect of emotions on structural 
changes. 
3. Emotional contacts and exposures. 
4. Commonest emotional components of 
structural disease: 
a. Infantile reactions (regressive in na- 
ture) . 
b. Repression of hostility. 
c. A stepped-up pace of life. 
In association with this lecture, a movie is 
shown which beautifully illustrates the influ- 
ence of emotions on bodily function and vice 
versa. All emotional reactions have certain 
physical accompaniments. With fear, tachy- 
cardia, palpitation, nausea, vomiting and other 
symptoms result. 
Similarly, a physical sensation such as severe 
acute abdominal pain results in the emotional 
manifestation of apprehension or fear. An in- 
dividual cannot be sick only in body or only in 
his mind. This relationship between mind and 
body is a constant and dynamic one. Psycho- 
somatics is a point of view rather than a body 
of knowledge. We must abandon the dualistic 
concept that the disorder is either functional 
or organic. 
Terminology may often be a strait jacket to 
our thinking. An aviator who is frustrated by 
his responsibilities and tasks, and who gener- 
ates excess acid may develop acute abdominal 
pains and eventually get enough erosion of the 
gastric mucosa to produce an ulcer. If we 
diagnose this peptic ulcers, we automatically 
think of treatment by diet, powders, or surgery. 
If we formulated the case into the total person 
terms, we might appropriately think of man- 
agement by changing the job situation or re- 
ducing the emotional tension. A diagnostic 
formulation such as “worry over job, fear at 
competition, panic at jeopardy of his status and 
living standards resulting in excess gastric 
acidity” would be more helpful in our thinking 
than a simple diagnosis of ulcer, although ad- 
mittedly no hospital record committee would 
accept it. 
We must understand that emotions can and 
do produce structural changes through affect- 
ing the tonus, secretion and circulation of tis- 
sues and organs. If we admit that a single 
severe emotional experience can produce a 
transient rise in blood pressure, why can’t we 
accept the thesis that nagging, prolonged frus- 
tration can and does produce a prolonged or 
permanent hypertension. 
We must also recognize the result of emo- 
tional contacts, particularly in the early de- 
velopmental years of an individual’s life. Later 
emotional exposures are also important. One 
man is exposed to the bacteriological trauma of 
a roommate with active tuberculosis; whereas 
another man has a roommate with heart disease, 
who lives in constant contemplation of sudden 
death. Certainly both are real exposures. 
The commonest emotional components of 
structural disease are: (a) infantile reactions 
(regressive in nature); repression of hostility, 
and (c) a stepped-up pace of life. The doctor 
must be able to assay the environmental forces 
acting on his patient and be able to manipulate 
these for the patient’s welfare. He must also 
be able to modify the patient’s own goals, 
ambitions, and demands in a realistic way. 
References: 
(Y)—pap:es 251-277. 
LECTURE NO. 14 
Events which precipitate a neurosis; and 
emotions and their effect on the body. 
Crises at which vulnerable personalities tend 
to break down: 
1. Puberty. 
2. Leaving school. 
3. Love affair. 
4. Marriage. 
5. Bearing or fathering a child. 
6. Vocational or financial disappointments. 
7. Loss of a loved one. 
8. Threats from environment. 
AGE OF ADULT NEUROSIS 
Nature of adult deprivation: 
1. In single people. 
171 AVIATION MEDICINE PRACTICE 
2. Married women. 
3. Married men. 
4. Financial insecurity. 
5. Need for aggression. 
6. Disappointment in loved object. 
7. Career women. 
8. Discussion regarding real illness and 
neuroses. 
9. Appendix removal. 
10. Approach of involutional period. 
There are crises in every life, and at these 
points the vulnerable personality tends to break 
down. (See outline). In the past we have been 
prone to think of a neurosis as resulting from 
a major catastrophe. It is true that such events 
may precipitate a neurotic outbreak, but many 
begin without any such event in close relation 
to the onset. It is usually a culmination of 
events and forces, often difficult to piece to- 
gether, which precipitated the final break. 
Most adult neuroses break out between late 
adolescence and 35 years of age, when in a 
period of increasing responsibilities an effort 
is being made to establish oneself socially, 
economically and with his sexual instincts. This 
is a period with frustrating and disappointing 
experiences, many of which are similar to the 
original ones in childhood. 
In single people, a neurosis may occur gradu- 
ally following a second marriage of a parent. 
This may reawaken and disappoint an oedipal 
attachment. Married women may gradually de- 
velop a neurosis when their fantasied desires 
in marriage are not fulfilled. Some women ex- 
pect the impossible in marriage. When they can 
verbalize their feelings, they often realize that 
their partner is not enough like some childhood 
image, usually the father. 
An unwanted pregnancy may lead to anxiety, 
depression, and G. I. symptoms because the 
patient is too psychically immature to want a 
child. At a deeper level, it may represent a long- 
desired yet feared competition with her mother 
and arouse much guilt. A married man may 
become neurotic because his wife is not enough 
like the mother, because he cannot have the 
dependent role he wishes as he is temporarily 
dislodged from his wife’s affection by the birth 
of a child, or by slow failure to reach a desired 
goal or a position of prominence which is seen 
unconsciously as a thwarting from a superior. 
The human psyche is not an area of harmony; 
it is a continued battleground of conflicts and 
trends, mostly from the dynamic instincts of 
sex, self, and herd. Usually the respective de- 
mands are in conflict with each other and are 
often irreconcilable. The friction of emotional 
conflict cannot be continued forever, nor can it 
remain in status quo. The emotional cross-pur- 
poses must be relieved or compromised, even if 
the compromise be a pathological one. Every 
pathological solution of the emotional conflicts 
gives rise to psychoneurotic manifestations. 
Basic patterns of emotional conflicts are end- 
lessly repeated, filled with disappointments, 
marital difficulties, rejections in love life, eco- 
nomic reverses, etc. These and many other life 
situations tend to bring on anxiety, which over 
a long time takes a heavy toll of the mental 
resistance and often disrupts the personality. 
In aviation medicine, having decided the ill- 
ness of an individual is psychosomatic, the 
flight surgeon’s next step is to locate the source 
of emotional difficulty. Sometimes it is apparent 
in the life situation of the patient; at other 
times it is not so simple and may lie buried in 
the unconscious of the patient, who will not 
know anything about it except as it produces 
a chronic feeling of uneasiness or anxiety. The 
flight surgeon may then rightfully refer the 
patient to a psychiatrist. 
References: 
(J)—chapter 14. 
(S)—pages 18-21. 
(X)—pages 511-529. 
LECTURE NO. 15 
Neurasthenia: 
Outstanding complaints: 
1. Fatigue. 
2. Somatic discomforts. 
3. Mild mood disturbances. 
Objective findings. 
Etiology and structure. 
Illustration of investing objects with libido. 
Differential diagnosis. 
Prognosis. 
Treatment and management. 
Neurasthenia is a term of Greek derivation, 
literally meaning lack of nerve strength, first 
used by Beard in 1869. It now has a more 
limited meaning than formerly, although all 
172 Chapter 9. — NEUROPSYCHIATRY IN RELATION TO AVIATION MEDICINE 
psychiatrists do not agree on its being a separ- 
ate entity. Generally it covers the three out- 
standing complaints of fatigue, various poorly 
defined somatic discomforts, and mild mood 
disturbances. The fatigue is the most constant 
and usually the first symptom mentioned. It 
may be tiredness after minimal exertion or con- 
stant fatigue independent of exertion. 
It makes him think himself organically ill. 
The somatic discomforts are many and varied, 
may be recited glibly, and include palpitation, 
anorexia, post-prandial discomfort, gas forma- 
tion, constipation, headaches, sensation of pres- 
sure on top of the head, a bandlike constricting 
sensation, dizziness, spots before the eyes, etc. 
The most common mood distubances are irrit- 
ability and mild depression. Patient is gloomy, 
introspective, unable to concentrate. He lacks 
self-confidence; problems in the sexual sphere 
are common, including impotence, frigidity, and 
disgust, all of which are indicative of general 
maladjustment of the love life of either sex. 
The objective findings include loss of weight, 
low blood pressure, vasomotor lability, the mood 
reflected by the facies or posture; while ex- 
amination of the body systems reveals normal 
function. The etiology is defective personality 
development permitting conflicts. While over- 
work has been blamed, we rarely find a neuras- 
thenic who is ever overworked. Those who do 
not accept psychogenic origin seek some 
somatic or organic pathology to explain what 
is seen, and often pounce upon some minor 
deviation and over-treat this, with no result 
save discouragement for the patient and the 
doctor. 
What is the etiological structural pathology 
in neurasthenia, or how do we get the present- 
ing complaints? We recall that in the discus- 
sion of libido development, we recognized the 
infant’s early interest in himself. Later, after 
the narcissistic stage, comes an interest in 
others, which is more or less sexually tinged. 
The interest and sexual component cannot be 
separated successfully; consequently if the 
sexual interest is frowned upon, rejected or 
punished, it finds only limited gratification in 
these love objects and returns with itself. 
With curtailment of outside interests, self- 
interest grows proportionately; and this fact 
of self-preoccupation has long been stressed in 
the neurasthenic. When the capacity to choose, 
or no desire to choose an external object exists, 
the fantasy life absorbs libido, resulting in in- 
activity, poor concentration and dissatisfaction. 
Perverted organ function, fatigue, and symptom 
formation may result. Added tension comes 
from the frustration and self-preoccupation. 
The individual feels vague needs are unsatis- 
fied. 
A differential diagnosis must include psy- 
chotic depression, schizophrenia, early paresis, 
early arteriosclerosis, early tuberculosis, hypo- 
thyroidism, various blood dyscrasias, ulcer, 
neoplasm, and, rarely, Addison’s Disease. 
Once the diagnosis of neurasthenia is made, 
we must recognize we have a serious problem. 
The prognosis is variable. It is better in acute 
cases with a sudden appearance of symptoms. 
In longer standing cases, treatment is much 
more difficult. Certain neurasthenias approach 
psychoses in psychic structure. The most suit- 
able treatment is probably psychoanalysis. 
When this is impossible, less intensive psycho- 
therapy along the lines of recognition that no 
infectious or structural changes exist to ac- 
count for the symptoms, that the difficulties 
exist in the psyche and that concentration upon 
these problems may result in improvement, is 
taken. The more the patient can be helped 
to see where emotional satisfactions are to 
be gained in the outside world, the less psychic 
energy there is left to stagnate in the body to 
produce discomfort. 
References: 
(A)—pages 138-141. 
(F)—page 32. 
(J)—pages 194-208. 
(X)—pages 534-540. 
LECTURE NO. 16 
Anxiety Hysteria: 
Anxiety hysteria: 
Types. 
1. Primary. 
2. Ego. 
3. Mutilation. 
Clinical manifestations: 
1. Sudden feeling of discomfort and ap- 
prehension. 
2. Somatic manifestations. 
Phobia. 
173 AVIATION MEDICINE PRACTICE 
Etiology and psychopathology. 
Differential diagnosis. 
Prognosis. 
Treatment: 
1. Psychoanalysis. 
2. Primary requisites: 
a. Knowledge of the structure of 
neurosis. 
b. Time. 
c. Cooperation on patient’s part. 
This is probably our most common neurosis 
today. The three types of anxiety are: primary, 
or the anxiety incident to psychic helplessness 
in early life; ungratified hunger needs lead to 
this anxiety. Ego anxiety occurs later, when 
the life situation threatens a return of early 
psychic helplessness. Mutilation anxiety, or 
fear of bodily harm, is a retaliation for aggres- 
sive fantasies of a sexual or other nature. This 
awakens early fears based on the childhood be- 
lief in retaliation. 
The clinical manifestations include a sudden 
feeling of discomfort and apprehension, intense 
mental suffering, sometimes definite fears of 
insanity or impending death. Somatic mani- 
festations include palpitation, sweating, dizzi- 
ness, dyspnea, trembling, nausea, “terrible all- 
gone feeling,” etc. These may occur either night 
or day. They are very incapacitating; attacks 
last a few minutes with gradual subsidence. 
The patient gradually modifies his activities in 
such a way as to attempt to avoid the attacks. 
This attempted avoidance is termed a phobia. 
Some common phobias are fear of going alone 
in the streets, fear of crowds, of riding in pub- 
lic conveyances, of closed spaces, open spaces, 
of dirt, etc. These enlarge to increasingly cur- 
tail healthy activity. 
If primary anxiety in the infant is too fre- 
quent or too overwhelming, unconscious memor- 
ies of it remain to show themselves later when 
the individual perceives a warning of impending 
helplessness. Early childhood disappointments 
and frustrations lead to aggressive hostile fan- 
tasies which stimulate a fear of retaliation 
or punishment, and anxiety results. Every 
adult anxiety hysteria is considered a replica 
of a childhood experience. The phobia projects 
an inner danger outward, so that the ego is in 
the middle, between the dangers of instinctual 
demands and the dangers of the outside world. 
The unsolved oedipus complex is considered the 
kernel of the neurosis, in that the child’s fear 
of the dreaded rival parent is displaced, so the 
child can go on living with and loving the 
parent by avoiding the substitute. It is im- 
portant to realize that the phobias are in them- 
selves results of the process of substitution, 
and that one must look beneath the surface 
for the causative agent. 
Anxiety hysteria must be differentiated from 
a cardiac crisis, G. I. dysfunction, and schizo- 
phrenia. Some familiarity with the syndrome 
will make it readily recognizable. The prognosis 
is not as good as for conversion hysteria, but 
better than neurasthenia. The earlier in life 
it is treated the better. These patients are very 
adept at self-defense. The prognosis depends 
on the length of time the attack has been going 
on and the skill of the physician. 
References: 
(R)—pages 193-215. 
LECTURE NO. 17 
Conversion hysteria: 
Symptomatology: 
1. Sensory phenomena. 
2. Motor phenomena. 
3. Convulsive seizures. 
4. Visceral phenomena. 
5. Vasomotor disturbances. 
6. Psychic phenomena. 
7. Somnambulism. 
8. Dual personality. 
9. Hysteric catalepsy. 
10. Hallucinations. 
12. Occupational neuroses. 
13. War neuroses. 
Etiology and psychic structure: 
Psychological occurrences in genesis of at- 
tack. 
Differential diagnosis. 
Prognosis. 
Treatment. 
There are few symptoms of organic disease 
that this complex medical entity cannot simu- 
late. It was one of the first neuroses to be 
studied widely, and the French school, includ- 
ing Charcot, Bernheim, and Janet, worked in- 
tensively with hysterics. Mood and character 
changes as well as physical or somatic altera- 
tions are prominent. Traumatic neuroses or 
174 Chapter 9. — NEUROPSYCHIATRY IN RELATION TO AVIATION MEDICINE 
traumatic hysteria, which were loosely called 
war neuroses, are important to the flight sur- 
geon. Shellshock, concussion neuroses, exhaus- 
tion neuroses, etc., belong in this category. It 
is difficult to evaluate the results of actual tissue 
injury and the results of fear, fright, and 
threat to the organism’s integrity. In these 
so-called traumatic neuroses, there is a prepond- 
erance of headache and dizziness, with mental 
symptoms of headache, depression, and impair- 
ment of memory. 
Terrifying dreams may occur. Often an ele- 
ment of compensation plays a large role in the 
continuation of symptoms. One sees many cases 
where seemingly more could be gained by get- 
ting well than by holding out in this way for 
compensation; yet the patient prefers to over- 
look his future adjustment and tends to con- 
centrate too much on the immediate problems 
of restitution. 
Charcot called hysteria a psychosis produced 
by ideation and responding to suggestion. It 
is not currently considered a psychosis but 
rather a neurosis, and it was Freud who showed 
the importance of unconscious conflicts and of 
early sexual trauma. He considered it the dis- 
torted expression of unconscious mental con- 
flicts, the symptoms being attempted defenses 
against instinctual desires which threaten to 
break through. 
The character of the hysteric is infantile. 
The patient demands a great deal of attention, 
and is sensitive to the necessary daily frustra- 
tions of life. He has feelings of inferiority, a 
great craving for expressions of love, is change- 
able in his affections, and lacks the capacity to 
love in an adult, altruistic way. He is an open 
personality who can quickly make friends, even 
strong attachments, but eventually his friends 
disappoint them, since their demands are so 
great. 
The psychological occurrences in the genesis 
of the attack are, according to Pearson and 
English: 
1. Deprivation with resulting anxiety. 
2. Introversion or withdrawal of libido and 
failure to retain contact with the environment 
and maintain relationship with people. 
3. Regression to earlier mode of reaction. 
4. Return of the repressed oedipal wishes. 
5. Symptom formation as the solution of 
conflict. 
In differential diagnosis, a suspicion that 
hysteria exists should not preclude any reason- 
able examinations that would reveal organic 
disease. One distinctive factor in hysteria is 
la belle indifference. The prognosis, while good, 
still must recognize that a disturbance in the 
personality of considerable magnitude exists. 
Treatment may be lengthy, and to be success- 
ful must depend largely on understanding the 
forces at work in the condition. Modification 
of the environmental conditions, plus modifi- 
cation of the patient’s attitude, is essential. 
References: 
(J) —pages 210-237. 
(K) —pages 47-54. 
(R)—pages 216-235. 
(X)—pages 540-560. 
LECTURE NO. 18 
Psychopathic personality: 
Cause. 
Distinction from other personality disorders: 
1. Psychoneuroses. 
2. Mental defective. 
3. Ordinary criminal. 
General picture: 
1. Superficially attractive. 
2. No irrationality, marked nervousness, or 
other symptoms of psychoneurosis, 
3. No sense of responsibility. 
4. Total disregard for truth. 
5. Accepts no blame—employs mechanism 
of projection. 
6. No sense of shame. 
7. Offensive conduct without apparent cause. 
8. Lack of interest in financial success. 
9. Most outstanding trait—inability to profit 
from experience. 
10. Egocentricity. 
11. Poverty of affect. 
12. Lack of insight, 
13. Alcoholic indulgence—peculiar pattern. 
14. Peculiar sex life. 
15. Not prone to suicide. 
16. Inability to follow life plan consistently. 
17. Striving for failure. 
Borderline psychopathic personality; 
1. In Naval service. 
2. In aviation medicine. 
Psychopathic personality in the military serv- 
ice. 
This is a vague diagnostic category covering 
175 AVIATION MEDICINE PRACTICE 
a wide variety of maladjusted people who can- 
not be classed either as psychotic or psycho- 
neurotic, but who do have inadequacies of per- 
sonality structure resulting in their being so- 
cially maladjusted persons. When lifelong ab- 
normal behavior is antisocial, egocentric and 
unaltered by experience, the diagnosis of 
constitutional psychopathic inferiority is ap- 
propriate; whereas if the outstanding charac- 
teristics are not primarily antisocial, but rather 
those of inadequacy coming on around adoles- 
ence, the diagnosis of personality disorder is 
more appropriate. The psychopath exhibits a 
particular type of emotional immaturity, with 
strong drives for immediate satisfactions and 
pleasure without regard for the future. 
This condition must be distinguished from 
psychoneurosis, wherein, the patient is anxious, 
unhappy, or obsessed with thoughts he recog- 
nizes as absurd. The psychopath shows none 
of the usual neurotic picture, he tends to act 
out his conflicts, with resulting suffering and 
unhappiness for those in his environment, but 
with little conflict or guilt feeling. He is hard, 
in contrast to the sensitivity of the neurotic. 
The mental defective is obviously stupid, and 
his follies may be readily understood as result- 
ing from his lack of intelligence; the ordinary 
criminal works consistently towards his own 
ends; the psychopath seldom takes advantage 
of what he gains, and almost never works 
consistently in crime or anything else to achieve 
prominence. The criminal’s end can usually be 
understood by the average man. The psycho- 
path’s end is not so readily understood. His 
antisocial actions are incomprehensible and 
often for no material gain. His general picture 
is given in the outline above. 
In the naval service, the borderline psycho- 
path presents perhaps a greater problem than 
the true psychopath, particularly in regard to 
the magnitude of the problem. These people 
prove inadequate to the complete fulfillment 
of their duties and must be considered both 
by medical and disciplinary authorities. 
The borderline psychopathic personality ac- 
counts for a large portion of our maladj ustmenst 
in the naval service. Many of these maladjust- 
ments are incidental to the service and actually 
extend back years prior to entrance, resulting 
primarily from a personal inadequacy. In 
civilian life these people were sufficiently pro- 
tected by their families, and their communities, 
to prevent serious difficulties in their daily 
routine. In service, they are deprived of this 
protection and immediately begin to experience 
difficulties. The majority are disloyal to any 
organization, are easily suggestible, and as a 
result are in constant difficulty. They lower 
efficiency and impair morale. They form a large 
number of absentees, the discontented, the in- 
efficient, the inmates of the brig, and the 
frequent visitors to sick bay. They are useless 
to the service. 
References: 
(C) —all of this reference. 
(D) —pages 504-520. 
(X)—pages 495-510. 
Article by Bloom in Cosmopolitan Magazine, February 1948 
issue. 
LECTURE NO. 19 
The psychiatrist in a dispensary ; 
Psychiatry as a medical science really began 
in the latter part of the 19th and the early 
part of the 20th century, when such men as 
Kraepelin, Prince, Freud, Meyer, and White 
began their memorable contributions to the 
study of the human mind. 
Thirty years ago, many first-class medical 
schools did not provide their students, internes, 
and residents with any systematic psychiatric 
training. 
In the past three decades, there has been a 
rapid development and extension of the field 
of psychiatry. An important step forward was 
the child guidance movement beginning in 1920 
under the influence of Dr. William Healey. 
As early as 1909, the Surgeons General of 
both the Army and the Navy accepted the in- 
vitation of the Superintendent of St. Elizabeth’s 
hospital in Washington, D. C. to assign medical 
officers to that institution for instruction and 
study. This was the beginning of graduate 
training in psychiatry for the armed services. 
Recognition must be given to Colonel Thomas 
W. Salmon, MC, U. S. Army, and to Dr. William 
A. White for their scholarly contributions to 
military psychiatry during World War I. 
In the past 10 years, the field of psychiatry 
has made further progress, both in its con- 
tribution to the health of the nation and its 
acceptance by the general public. Psychiatry 
was placed on the same plane with medicine 
176 Chapter 9. — NEUROPSYCHIATRY IN RELATION TO AVIATION MEDICINE 
and surgery by the military forces in the late 
war, and the opportunity was thus provided 
for psychiatry to take its proper place as a 
major member in the constellation collectively 
known as the healing arts. The establishment 
by the Veterans Administration and by our 
larger American cities of mental hygiene clinics 
to provide the necessary out-patient care to 
the emotionally handicapped veteran and the 
troubled citizen has been another step forward 
in the emancipation of the specialty from the 
cloistered State hospitals to the place it should 
have in the community. 
Concurrent with the spread of psychiatry to 
the general public, there has been increased 
emphasis on prevention rather than custody, 
and therapy rather than diagnosis and disposi- 
tion. With the appropriate shift in emphasis 
to prevention has come increased acceptance 
of the specialty by the public and a decrease 
in the hesitancy of the individual to seek 
psychiatric assistance. 
Naval medicine has long provided competent, 
well-trained psychiatric personnel for the major 
naval hospitals, prisons, and training stations. 
The Navy has been ahead of its civilian count- 
erpart in that almost all naval hospitals have 
had a psychiatric service as an integral part of 
the organization. The drive to have such a 
service in all large civilian hospitals is making 
progress, but much yet remains to be done to 
achieve this undeniably desirable goal. Keyes, 
Bookhammer, and Kaplan, writing in the 
American Journal of Psychiatry, August 1948, 
reported a study of the consultations done by 
a psychiatric service in a six-months period 
at the Jefferson Medical College hospital. They 
found that 81 percent of the patients referred 
for study consisted of psychosomatic disorders 
or psychoneuroses. 
It is believed that in the large dispensary 
such as one finds at our naval air stations there 
is an even greater opportunity for service by 
medical officers trained in psychiatry than has 
heretofore been recognized. Captain Francis 
J. Braceland has pointed out that wartime 
experience in the field of psychiatry in the 
Navy showed that the neuroses and psycho- 
pathies in general made up more than 90 
percent of the neuropsychiatric problem during 
the war; while hospitalized psychotics amounted 
to one per thousand personnel per year, and 
represented less than ten percent of the hos- 
pital psychiatric problem, to say nothing of 
the over-all psychiatric picture. 
General Menninger, in discussing the Army’s 
experience in psychiatry during the war, stated 
that the neuroses, psychopathic personalities 
and mental defectives constituted 93 percent of 
the admissions to hospital psychiatric services; 
and further stated that for every psychiatric 
patient hospitalized, three or more were seen 
in facilities other than hospitals for psychiatric 
help. He went on to point out that the vast 
majority of psychiatric cases seen in the Army 
were mild maladjustments and neurotic reac- 
tions; whereas the major portion of the civil 
practice had long been with psychotics. 
Let us now look at the role of the psychia- 
trist serving outside a naval hospital. In any 
naval community, problems are constantly aris- 
ing wherein psychiatric help would be useful. 
Among these, consideration may be given to 
the young enlisted man fresh from training 
camp who finds difficulty in integrating himself 
to service life. Many of these apparently mal- 
adjusted young men would profit from psychia- 
tric study and counsel. In this manner the 
work of the personnel officer and the command 
may be lessened by the avoidance of the ad- 
ministrative problem the misunderstood misfit 
becomes as he fights his conflicts through ir- 
regular behavior. 
Those obviously inadequate, inapt, immature, 
and those suffering from longstanding person- 
ality disorders which militate against successful 
service, can be readily identified and should 
be eliminated by administrative discharge. This 
saves both time and money for the service 
by avoiding unnecessary hospitalization. 
Admiral Dallas G. Sutton, long active in the 
field of psychiatry in the Navy, corroborates 
this point when, writing in the Naval Medical 
Bulletin, he states: “Under normal conditions 
the loss of man days attributed to the study 
and hospitalization of psychiatric cases is very 
considerable.” Many of the new men with 
adaptational problems are salvageable through 
understanding advice and proper placement. 
Personnel officers are quick to cooperate with 
the psychiatrist in these matters, for a well- 
adjusted man reduces their problems and con- 
177 AVIATION MEDICINE PRACTICE 
tributes to the over-all efficiency of the com- 
mand. 
Another field of service is with the psycho- 
somatic illnesses. The concepts of inter-reaction 
of mind and body in the production of sym- 
ptoms have long been established. Strecker, 
Weiss, English, and others state that from 50 
percent to 75 percent of all patients appearing 
in the offices of the general practitioner have 
illnesses with a large emotional component. The 
experienced naval medical officer would readily 
agree that elimination of the traumatic cases 
would leave the percentage ever higher. These 
men come in with real complaints of illnesses 
known so often to be functional: headache, 
nausea, vomiting, asthma, diarrhea, epigastric 
pain, and certain skin conditions. They merit 
more attention than the brief encounters they 
sometimes get from the medical officer. Quickly- 
ordered and dispensed standard remedies do 
not always suffice in these cases. Many of 
these functional complaints can be relieved only 
by psychiatric treatment. 
Marked improvement in efficiency and saving 
in manpower can be effected when such treat- 
ment is available. This is not to imply that all 
non-psychiatric medical officers are ignorant of 
the more common psychotherapeutic procedures; 
but in these days of understaffed dispensaries 
and harrassed, overworked medical officers, there 
is often not sufficient time available to handle 
such cases in the manner the medical officer 
himself may recognize as necessary. It is main- 
tained here that the availability of a psychia- 
trist will enhance the quality of medical care, 
and at the same time improve the morale of 
the medical staff. 
Another field for the psychiatrically trained 
medical officer is in the study of men facing 
disciplinary action. The responsibility for the 
punishment of the offender in the naval service 
lies with the command. More and more, com- 
manding officers are showing not only their 
willingness but their desire to have these men 
studied by psychiatrists in an effort to de- 
termine the forces at work in their anti-social 
or delinquent behavior. 
A life history from the longitudinal view- 
point, a psychometric and attitudinal study, and 
an estimate of the strength of the various 
forces at work in the personality will shed 
light on the conflicts of the man and his failing 
adaptation. Such information and advice to the 
responsible officer or court martial enables con- 
sideration of important and appropriate factors 
before action is taken. In a similar manner the 
psychiatrist can aid both the command and 
the individual patient in cases of suspected or 
actual sexual deviation and of alcoholism. 
Still another area where psychiatric aid is 
necessary is in the care of dependents. These 
patients will be found to constitute a large part 
of the total number of patients served. They 
present problems which vary from requests for 
advice concerning “problem” children or mari- 
tal maladjustment, through the various mild 
somatic and psychic manifestations of tension 
states, to the frank psychoneuroses and psy- 
choses, Although it is the policy of the Navy 
to provide medical care for dependents of naval 
personnel, as yet no steps have ben taken to 
furnish hospitalization for psychiatric patients 
in this category. It is certain that the avail- 
ability of psychiatric help can be an asset to 
the mental health of the naval community and 
prevent in some cases the actual personality 
disruptions which necessitate hospitalization. 
Experience has shown that adaptation to the 
military environment, with its attendant regi- 
mentation and reduced opportunities for indi- 
vidual expression, works a hardship on the 
feminine members of the service, perhaps in 
a greater degree than on their brothers-in- 
arms. On the other hand, it is to the credit 
of the opposite sex that so many were able 
to make the transition to military life during 
the past war, often with an efficiency and sense 
of personal satisfaction not previously achieved 
in civil life. It is felt that psychiatric assistance 
plays a role in continuing the successful in- 
tegration of women into the naval service. 
Marital and family problems of both officers 
and men frequently arise wherein services are 
needed that neither the chaplain nor the legal 
officer can provide. Medical officers who are 
trained to appreciate the variations in per- 
sonality organization, and the psychological 
needs of the individual, can often assist patients 
to understand and solve the conflicts which 
arise in the family circle. In so doing, they are 
contributing not only to the mental and social 
health of the community, but to the efficiency 
178 Chapter 9. — NEUROPSYCHIATRY IN RELATION TO AVIATION MEDICINE 
of the naval personnel involved. 
It is the writer’s opinion that a psychiatrist 
should be available at all large dispensaries. A 
relatively large naval community may be served 
on an out-patient basis by one medical officer 
so trained. Dr. Morris Levine, in reference (M), 
discusses some 40 methods of psychotherapy 
for the mentally or emotionally ill patient. 
Study reveals that 35 of these techniques are 
suitable for use on an office or out-patient 
basis. Dispensary psychiatrists could, and 
should be, looked upon in a sense as engaged 
in preventive medicine. They should be seeing 
patients who are in the incubation stage of 
emotional illness while tension is the predomi- 
nant etiologic factor, and before the appear- 
ance of such disorders as ulcers, hypertension, 
asthma, and chronic gastro-intestinal dysfunc- 
tions, which would necessitate hospitalization. 
Keeping men on the job both prevents lost 
manpower and lessens the patient load for the 
hospital staff. We know that wartime experi- 
ence conclusively showed treatment near the 
front lines to be more effective than treatment 
in the rear areas. In like manner it is main- 
tained that treatment while the patient is still 
on the job is much more effective than after 
he has been hospitalized. In addition, we can 
thus avoid the psychic contagion often seen 
in hospital wards when the medical discharge 
of one or two patients results in other poorly 
motivated personnel becoming “survey happy.” 
Admiral Swanson, our Navy Surgeon General, 
speaking to the Reserve Naval medical officers 
at a recent meeting of the American Psychiat- 
ric Association, firmly supported these ideas 
when he said: “Let me say most emphatically 
that, as I see it, the responsibility of psychiatry 
in the armed forces is by no means one solely 
of eliminating the obviously unfit; psychiatry 
can be of great significance in assisting our 
training officers to discover the spark of posi- 
tive motivation in new recruits, and to point 
the way of fanning this spark into the flame 
of effective, responsible personnel; and beyond 
all this, we must explore the possibility of a 
really preventive psychiatry in our training 
centers and schools, and in operational and 
combat units.” 
Commander Thomas A. Harris called the 
attention of the American Psychiatric Associa- 
tion to the role of the psychiatrist in the 
future. He pointed out the devastating psycho- 
logical effects of atomic warfare on initiative 
and personal effectiveness through demoralizing 
hysteria, and expressed a hope psychiatrists 
could prepare the civilian population to cope 
with these tendencies. 
Aviation activities offer an unusual opportun- 
ity for the services of a psychiatrically trained 
medical officer. Here, in an environment where 
even the routine daily training activities pose 
a constant threat to the safety of the individual 
flyer, tension states of varying degree present 
an ever-present problem for the Medical De- 
partment. It is an impossible goal to expect 
selection processes to eliminate these hyper- 
reactive individuals, and it is not necessarily 
a desirable goal. It is felt that any aviation 
activity of appreciable size should have a 
psychiatrist who is also a flight surgeon as an 
important member of the medical staff. 
Other places where a psychiatrist can be 
efficiently and effectively utilized are at the 
larger naval schools, with task groups, and 
with fleets. 
It is suggested that the assistant staff medical 
officer of major air commands, both training 
and operational, should be a medical officer with 
graduate training in psychiatry. It is perhaps 
appropriate here to suggest, too, that the addi- 
tion of a psychiatrist to the teaching staff of 
the General Line School would be a definite 
step forward in the general orientation of the 
younger line officer. This would enhance his 
understanding of the dynamics of inter-per- 
sonal relationships, and thus would contribute 
to his over-all ability as he progressed to com- 
mand rank. 
The type of medical officer best qualified to 
discharge the duties outlined in this paper is 
one in the intermediate ranks who has had a 
good general medical background with graduate 
training in the field of psychiatry. It is not 
necessary that the men in these billets be 
certified by the American Board of Psychiatry, 
although such added qualification is desirable. 
Flight surgeons have in general had a better 
grounding in psychiatry than the general serv- 
ice medical officer, and in many instances would 
179 AVIATION MEDICINE PRACTICE 
be qualified to serve in such a billet as outlined, 
providing at least one, preferably two, addi- 
tional years of graduate training in psychiatry, 
either in naval or civilian facilities, was 
afforded. In order to avoid the assumption of 
a label as a “specialist” too early in their 
service careers, these medical officers should 
stand all regular watches and collateral duties. 
Care of . gynecological, pediatric, urological, 
E.E.N.T., and general medical cases on watches 
is considered a necessary part of the profes- 
sional experience of these medical officers. In this 
manner they do not sacrifice their all-round 
medical ability, which has long been a source 
of personal and professional pride to the career 
naval medical officer. 
At the large stations a psychologist who can 
serve as an assistant to the psychiatrist is 
considered an invaluable colleague. This is in 
line with the experience in the military services 
during World War I, when they cooperated 
both in the selection and training of personnel. 
Furthermore, this follows in part the team idea, 
which proved to be so satisfactory in the 
hospital care of psychiatric patients during the 
past war. 
Since the cardinal mission of the Medical 
Department is to maintain the health of the 
service as well as to promote morale and to 
plan for increasing efficiency, it is maintained 
that the assignment of psychiatrists to dis- 
pensaries and the other extra-hospital func- 
tions is a desirable step forward toward the 
goal of providing mental hygiene clinics for 
service personnel. Certainly it must be recog- 
nized that the provision of such facilities for 
service people is a progressive step in the field 
of preventive medicine and fully as important 
as is the role of Veterans Administration or 
community mental hygiene clinics. For, to quote 
Dr. William A. White, “the production and 
maintenance of morale is a psychiatric problem 
that affects the whole nation at arms—the 
worker and the farmer, the parent and teacher, 
civilian administrative personnel, the executive 
department and the entire military and naval 
establishment. The protection of morale, of 
concentrated motivation, and of solidarity, are 
much more economical than are remedial efforts 
after disastrous failures,” 
SAMPLE EXAMINATIONS FOR THE 
STUDENT OFFICER S PRACTICE 
FIRST NEUROPSYCHIATRIC EXAMINATION 
Answer any six. Time 50 minutes. 
No. Value QUESTION 
Score: Question value indicated. 
1. (15) Discuss the reasons a flight surgeon 
should know something of neuro- 
psychiatry. 
2. (15) Discuss the body-mind reciprocal re- 
lationship. 
3. (15) Discuss the influence of environment 
on personality. 
4. (15) Outline the psychosexual development 
of the individual. 
5. (10) Identify and discuss briefly your 
ideas of Id, Ego, and Super-Ego 
and their relationships. 
6. (10) Discuss the psychoanalytic concept 
of “fixation” and its possible influ- 
ence on personality in later life. 
7. (10) Distinguish between conditioning and 
precipitating factors in the etiology 
of emotional illness. 
8. (10) List several sources of internal stress 
in military environment. Which 
two or three do you consider the 
more important? 
9. (10) Define and illustrate: 
a. Complex. 
b. Rationalization. 
c. Projection. 
d. Delusion. 
e. Identification. 
Take any six questions. 
1. (15) Discuss briefly the development of 
the personality as seen by the 
psychobiological adherents. 
2. (10) Mention five important points in his- 
tory-taking and six headings for 
the direct mental examination of 
a psychiatric patient. 
3. (10) Indicate the three major headings 
under which psychoses may be con- 
sidered and illustrate with two ex- 
amples of each group. 
4. (10) Discuss the constitutional psycho- 
pathic inferior. 
180 Chapter 9. — NEUROPSYCHIATRY IN RELATION TO AVIATION MEDICINE 
5. (10) List several types of possible trau- 
matic reactions and discuss the im- 
portance of an appreciation of 
these reactions in Aviation Medi- 
cine. 
6. (15) Define a psychoneurosis. List three 
types and illustrate the basic 
symptomatology in each. 
7. (15) What is meant by psychosomatic 
medicine ? Illustrate by a brief 
hypothetical case. 
8. (15) Identify a chronic alcoholic, give the 
etiology and your approach to 
treatment. 
To answer the following 20 questions make 
a + (true) or a — (false) for each question 
in the left-hand margin opposite each number 
as appropriate: 
1. The chronic alcoholic is a neurotic drinker. 
2. A girl usually undergoes one more stage 
than the male in the solution of the 
Oedipus Complex. 
3. Conversion hysteria is the only neurosis 
which does not show some impairment 
of sexual function. 
4. The personality type usually seen in the 
obsessive-compulsive neurosis is serious, 
and intolerant of human foibles. 
5. Emotional Problems of Living was written 
by Strecker and Appel. 
6. Progressive deterioration is an incidental 
finding in organic psychoses. 
7. Adolph Meyer introduced the concept of 
psychobiology. 
8. In infancy instinctual tensions are mostly 
from internal physiologic needs. 
9. Instincts do not follow the pleasure-pain 
principle. 
10. The superego shows no expression of the 
influence of the parents. 
11. Many principles of psychotherapy are con- 
trary to religious teachings. 
12. There are psychotherapeutic procedures 
which are not time-consuming. 
13. Cases of accidental homosexuality will 
rarely be seen by the naval medical 
officer. 
14. Secondary gains are a large factor in trau- 
matic neuroses. 
15. The rule that a person who is afraid of 
insanity does not become insane is true. 
16. The person who claims he will commit 
suicide is more likely to do so than the 
depressed patient. 
17. Treatment of obsessive-compulsive disease 
is usually unsuccessful. 
18. Action is a good outlet for anxiety. 
19. All unusual or bizarre thoughts indicate 
psychoses or abnormality. 
20. Daydreaming is a dangerous activity. 
MULTIPLE CHOICE 
1. You are asked by the air group com- 
manding officer to recommend a man to him to 
fill the following billets. Choose people in 
column 2 to match the billets in column 1 so 
that the man best suited by personality gets 
the proper billet. 
Air group historian. 
Engineering officer. 
Entertainment officer. 
Air combat intelligence officer. 
Athletic officer. 
A. Extroverted, husky, popular single man. 
B. Syntonic, popular, salesman type. 
C. Schizoid, erudite, literary college graduate. 
D. U. S. Naval Academy graduate, class 
1948-B. 
E. Older, calm, sincere officer with degree in 
business administration. 
F. High school graduate disinclined to exert 
self. 
G. MIT graduate, with degree in mechanical 
engineering. 
H. Passed-over lieutenant inclined toward ir- 
responsibility. 
2. You are at sea beginning a six-months 
cruise with a newly commissioned air group. 
Underline the cases you would be able to handle 
successfully aboard the carrier for at least six 
weeks: 
a. Mild anxiety state precipitated by 
financial worries. 
b. Acute alcoholism. 
c. Paranoid state. 
d. Personality disorder (immaturity). 
e. Catatonic schizophrenia. 
f. Petit mal. 
g. Old paretic showing some deteriora- 
tion. 
h. Acute transient tension state with 
headache. 
181 AVIATION MEDICINE PRACTICE 
i. Obsessive-compulsive state (klepto- 
mania) . 
j. Meningioma with acute symptoms. 
3. The universal goal of people is: (Under- 
line.) 
a. Financial success. 
b. A home, wife, and family. 
c. Peace of mind. 
d. Promotion. 
4. The dissimilar term in the following is: 
(Underline.) 
a. Projection. 
b. Disintgeration. 
c. Introjection. 
d. Rationalization. 
5. A psychiatrically trained medical officer 
can be of most service: (Underline.) 
a. Aboard ship with an operational 
squadron. 
b. At the college where midshipmen 
get their two years’ study. 
c. On major commanders’ staffs’. 
d. At the primary training level. 
6. Underline the word which is dissimilar: 
a. Libido. 
b. Anal sadistic. 
c. Latent content. 
d. Anergasia. 
7. Reassurance, desensitization, pentothal 
interview, education, and routinizing are all 
forms of: 
a. Hospitalization. 
b. Psychotherapy. 
c. Analysis. 
d. Psychobiology. 
8. Elation, flight of ideas, circumstantiality, 
and increased psychomotor activity are seen in: 
a. Hypomania. 
b. Frontal lobe tumor. 
c. Arteriolosclerosis cerebri. 
d. Psychomotor equivalent. 
9. Underline the dissimilar word: 
a. Pinel. 
b. Jones. 
c. Charcot. 
d. Freud. 
e. Strecker. 
f. Weir Mitchell. 
g. Bleuler. 
h. Breuer. 
i. Herschkowitz. 
COMPLETION 
1. Burlingame likens a balanced personality 
to a four-legged chair and maintains that any 
leg out of proportion causes an unbalanced per- 
sonality. The legs in such example are: 
1 
2 
3 
4 
2. The personality consists of three portions, 
according to the psychoanalytical school. These 
are: 
1 
2 
3 
3. One of the great foundation stones util- 
ized for the structure of psychoanalysis is the 
concept that mental processes actively function 
on what may be thought of as different strata 
or levels. These are called: 
1 
2 
3 
4. Three essential constituents of peace of 
mind are: 
1 
2 
3 
5. Three fundamental urges or instincts are 
those of: 
1 
2 
3 
6. A group of related ideas bound together 
by and striv- 
ing for action is collectively called a 
7. Disguises employed by repressed ideas 
and desires seeking reentry to consciousness 
are known collectively as 
Examples are: 
1 
2 
3 
8. Kretschmer classified people into four 
anthropological groups: 
1 
2 
3 
4 
182 Chapter 9. — NEUROPSYCHIATRY IN RELATION TO AVIATION MEDICINE 
While Sheldon in a somewhat similar manner 
classified people into three classes by physique: 
1 
2 
3 
and matched these by three temperament types: 
1 
2 
3 
9. According to Menninger some of the type 
personalities prone to have unusual difficulties 
under adaptational strain are: 
1 
2 
3 
4 
10 Some of the more important symptoms 
of anxiety hysteria are: 
1 
2 
3 
11. Some of the outstanding diagnostic cri- 
teria regarding the psychopathic personality 
are: 
1 
2 
3 
4 
12 Manic-depressive reaction, involutional 
melancholia, and psychotic depressive reaction 
are all classed as disorders, 
13. Some of the major psychoneurotic dis- 
orders, according to the new nomenclature, are: 
1 reaction 
2 reaction 
3 reaction 
4 reaction 
14. Illustrative somatization reactions are: 
1 reaction 
2 reaction 
3 reaction 
15. One of the most severe mental diseases 
without known organic patholgy is 
DISCUSSION 
1. A pilot in your air group begins to louse- 
up his landings. You note he is becoming ir- 
ritable and moderately aloof. You try to be 
friendly and offer to help if you can. He tells 
you to “mind your own G - - D business, 
Doc; I’m all right.” 
Briefly discuss what action on your part 
might be appropriate. 
SECOND NEUROPSYCHIATRIC EXAMINATION 
1. It is obligatory that any doctor practicing 
medicine, either in the civilian or military set- 
ting, must have: 
a. Maximum psychiatric information. 
b. No psychiatric information. 
c. A minimum of psychiatric informa- 
tion. 
2. The brain was declared to be the organ 
of the mind by: 
a. Hippocrates. 
b. Pythagoras. 
c. Galen. 
3. Chains were removed from mentally ill 
patients, and they were considered as patients 
rather than criminals, first by; 
a. Charcot. 
b. Jung. 
c. Pinel. 
4. In the field of psychiatry, there are 
numerous sub-specialties. Among these are: 
a 
b 
c 
d 
e 
5. In the daily practice of medicine, a large 
segment of functional sickness is seen. It has 
been said that such cases make up over 
percent of a doctor’s practice. 
6. Scientific research has still not isolated 
the specific etiological factor in such diseases 
as and 
7. Neguchi and Moore are best remembered 
for having demonstrated the 
in the of 
8. In regard to psychiatric illnesses, some 
of the more important predisposing causes are: 
a 
b 
c 
d 
e 
f 
9. Exciting causes of emotional disorders 
may be either preponderantly 
or 
183 AVIATION MEDICINE PRACTICE 
10. activate and energize 
behavior. 
11. Strecker classifies mental diseases as be- 
ing in one of the following three groups: 
a —— 
b : 
c 
Under a, some examples are: 
Under b, two examples are: 
Under c, two examples are: 
12. Behavior in schizophrenia is best de- 
scribed as being or 
The schizophrenic’s emotional life is strikingly 
Schizophrenia is usually 
classified in the following four sub-groups: 
13. Pyknics tend to be : 
or predominantly outgoing people, while the 
leptic type tends to be or 
predominantly ingrowing in personality. 
14. A psychiatric examination includes not 
only a physical examination but a. 
examination. Under the latter, the following 
headings should be considered: 
a 
b 
c 
d * 
e 
f 
15. Flight of ideas is a symptom most often 
seen in disease. 
16. Insight is the capacity of the patient to 
look at himself and his symptoms and 
that he is mentally sick. 
17. In organic psychoses, there is progres- 
sive deterioration of: 
a 
b 
c 
18. Paroxysmal cerebral dysrhythmia is also 
known as Manifestations of 
this illness are considered under the headings 
of , and 
19 is a progressive 
19 is a progressive 
degenerative disease of middle life entailing 
severe dementia and in which inheritance plays 
a significant role. 
20. Prominent disturbances of sensorium 
and consciousness varying in degree from mere 
clouding to a full-fledged delirium with marked 
motor activity, complete disorientation and a 
vivid illusory and hallucinatory content, are 
symptomatic of psychoses. 
21. A Philadelphia Cocktail, consisting of 
the intravenous administration of 100 cc. of 
50 glucose, 100 mgm. of thiamin chloride and 
30 units of insulin, is used in the treatment of 
, which is a 
delirium encountered in patients who use 
to excess. 
22. In bromide intoxication, a blood bromide 
concentration above mgm, is danger- 
ously high. The important aspect of therapy 
is the administration of 
23. Shellshock is actually 
, and the conflict is between 
the instincts of 
and the expectations and demands of 
24. Regression, rationalization, repression, 
projection, and introjection are examples of 
25. A spike and dome EEG tracing is char- 
acteristic of 
26. In the depressed phase of manic depres- 
sive psychosis, the thoughts become sluggish 
and are expressed with the greatest difficulty. 
This is known as In involu- 
tional melancholia, however, there is marked 
useless activity, and the depression is said to 
be an one. 
27. Hallucinations may occur in every psy- 
chosis except 
28. Delusions which are self-accusatory or 
in which the patient feels he has committed 
an unpardonable sin are most often seen in 
disease and in 
184 Chapter 9. — NEUROPSYCHIATRY IN RELATION TO AVIATION MEDICINE 
29. A thought which dominates the mind 
and personality of the patient and which can- 
not be put out of consciousness is known as an 
30. A person who cannot correctly relate 
himself as regards person, time, and place is 
said to be 
31. An important factor in aviation medi- 
cine, which may be responsible for marked 
behavior deviations, is 
32. An acute infectious disease which like- 
wise may cause marked behavior problems is 
33. The illness in which there is memory 
loss but fairly good appreciation of immediate 
impressions, and in which there is confabula- 
tion with falsification of memory, is known as 
34. A drug which is usually smoked in cig- 
arettes and which may produce serious mental 
disturbances, chiefly a manic-like delirium, is 
35. , more often unconsci- 
ous than conscious, is a vital and dynamic con- 
ception and considered basic as to psycho- 
pathologic mechanisms. 
36. The neurosis in which fatigue is so 
marked, and in which the patient may become 
hypchondriacal, even though she is organically 
sound, is known as 
37. An effective but pathologic device which 
enables the neurotic patient to escape the dis- 
approval of his own self-ideal and the con- 
demnation of the herd by so camouflaging 
unworthy motivations that even to that stern- 
est critic, his own ego, they appear satisfactory, 
even praisworthy, is 
38. Possibly the most serious disease menace 
of modern civilization is 
39. The disease in which delusions of perse- 
cution are prominent, and contact with reality 
is largely lost, and in which latent homosex- 
uality plays a definite etiologic role, is known 
as 
40. The type of schizophrenia which offers 
the poorest prognosis is 
41. is 
one of the main clinical territories of the spe- 
cial fears or phobias. It is important to remem- 
ber these phobias represent a 
for deeply-hidden psychopathologic material, 
and that the phobias exist in order to keep out 
of consciousness submerged complexes which 
the personality of the patient cannot face. 
42. thinking may re- 
main ruminative and not eventuate in compul- 
sive behavior. 
43. One of the most essential factors in 
treatment of functional emotional conditions is 
to keep the patient 
44. A life-long history of emotional in- 
stability, occupational inadequacy, impulsive 
conduct, absence of ethical and moral consid- 
erations, disregard of truthfulness, decency 
and social responsiveness, is justification for a 
diagnosis of 
45. The most important place for the psy- 
chiatrist relative to his service in a military 
organization is at the early stages of 
46. Whereas in World War I the common 
neurosis was a relatively simple, somewhat 
naive conversion hysteria, in World War II the 
preponderant psychoneuroses were 
47. In his personality traits, the alcoholic 
is more apt to be preponderantly an 
than an 
48. The person who cannot face reality 
without alcohol, and yet whose adequate ad- 
justment to reality is impossible so long as he 
uses alcohol, is known as a 
49. A return to a former somewhat primi- 
tive and rather childish type of behavior which 
has as its object the domination by the in- 
dividual of some life situations, is known as 
50. Flight into reality with destructability 
and accentuated psychomoter activity is char- 
acteristic of 
51. A disorder characterized by transient de- 
lusions of persecution, without the bizarre 
fragmentation and deterioration of the schizo- 
phrenic, is called 
52. A severe depression with self-blame and 
suicidal trends, but without the constitutional 
or recurrent tendency of true manic depressive 
disease, and in which the mind of the patient 
there is clear cause and effect connection be- 
tween the environmental vicissitudes and the 
depression suffered, is known as a 
185 AVIATION MEDICINE PRACTICE 
SEMINARS 
Seminar No. 1: 
Navy Film—The Neuropsychiatric Patient. Illustrat- 
ing the proper approach to the care of a mental case. 
Seminar No. 2: 
Psychiatric experiences in World War II. Presen- 
tation of articles and discussion. 
Reference: 
(Z) —complete article. 
Seminar No. 3: 
Combat fatigue. Discussion of appropriate method of 
handling. 
Reference: 
(AA)—Complete article. 
Seminar No. U: 
The technique of the neuropsychiatric examination. 
Reference: 
(T)—Pages 39-62. 
Seminar No. 5: 
Schizophrenia: 
1. Schizophrenic Dynamisms. 
2. The pattern of schizophrenia. 
3. Varieties of schizophrenia. 
4. Case presentation. 
References: 
(K)—pages 67-80. 
(Q)—section II. 
(X)—pages 407-450. 
Seminar No. 6: 
Manic depressive disease: 
1. Etiology, psychopathology, and symptomatology. 
2. Causes and symptoms. 
3. Manic states. 
4. Depressed and mixed phases. 
5. Depression. 
6. Physical symptoms, course, prognosis, and treat- 
ment. 
References: 
(BB)—Pages 130-136; 137-157; 166-175. 
(D)—Pages 396-426. 
Seminar No. 7: 
Navy film—Combat Fatigue, Psychosomatic Disor- 
ders. A dramatic presentation of patients suffering 
these disorders. 
Seminar No. 8: 
Written examination on Fundamentals of Psychiatry 
by Dr. Strecker. 
Seminar No. 9: 
Head injuries and cranial trauma: 
1. Concussion and contusion. 
2. Intra-cranial hemorrhage. 
3. Treatment. 
4. Complications. 
Seminar No. 10: 
Alcoholism. Speaker from Alcoholics Anonymous 
with group discussion. 
References: 
(DD) —complete. 
(EE)—complete. 
(X)—pages 236-255. 
References: 
(D)—pages 202-209; 272-288; 290-300; 323-330. 
(X)—-pages 182-195. 
(FF)—page 298. 
Seminar No. 11: 
Organic psychoses and epilepsy: 
1. Epilepsy; phychoses with epilepsy. 
2. Psychoses with cerebral arteriosclerosis and cir- 
culatory disturbance. Senile psychoses. 
3. Psychoses with epidemic encephalitis; psychoses 
with brain tumor; phychoses with organic change of 
central nervous system. 
References: 
(D)—pages 61; 511, 512. 
(J)—pages 286-310. 
(M) —complete. 
(R)—pages 554-589. 
(T)— pages 176-187. 
(Y)—pages 323-331; 368-406. 
Seminar No. 12: 
Psychotherapy 
Reports on current practices in the use of electro- 
shock, insulin shock, electronarcosis, hypnosis, pento- 
thal interview, etc. 
Seminar No. 13: 
National Film Board of Canada films: The Feeling 
of Rejection. The Feeling of Hostility. 
Seminar No. H: 
Neuropsychiatric evaluation of prisoners and failing 
flight students. 
The role of the flight surgeon in evaluating prisoners 
for courts and retraining commands, and the flight 
surgeon’s study of the student aviator having ground 
or air difficulties; discussion by the legal officer of the 
types of naval courts and the role expected of medical 
officers. 
References; 
(GG)—complete. 
Seminar No. 15: 
U. S. Army film, Shades of Grey. 
Seminar No. 16: 
Test of diagnostic ability with pseudo-dramatization 
of cases by instructor. 
Seminar No. 17: 
Journal reports. 
References: 
As listed under Journal References. 
Seminar No. 18: 
Case presentation of homosexuality: 
References; 
(HH)—pages 610-666. 
(R)—selected references. 
(H)—page 400, plus other references. 
(A)—pages 258-295. 
(J)—pages 276-285. 
(G)—pages 50; 143; 148; 226; 238. 
Seminar No. 19: 
Original cases for diagnosis. 
Each student is requested to prepare three hypotheti- 
cal psychiatric cases to be presented for diagnosis. 
Each abstract should be 300 to 600 words in length, 
present sufficient details for diagnosis, but not make 
the case too obvious. The goal is the preparation of 
186 Chapter 9. — NEUROPSYCHIATRY IN RELATION TO AVIATION MEDICINE 
succinct summaries, and the ability to make rapid diag- 
nosis on the possession of critical factors. 
REFERENCES—NEUROPSYCHIATRY 
A. The Human Mind, Karl A. Menninger, Alfred 
A. Knopf, New York, 1946. 
B. Peace of Mind, J. L. Liebman, Simon and Schus- 
ter, New York. 
C. The Mask of Sanity, Hervey Cleckley, M. D., 
The C. V. Mosby Company, St. Louis, Missouri, 1941. 
D. Modern Clinical Psychiatry, Arthur P. Noyes, 
M. D., W. B. Saunders Co., Philadelphia, 1940. 
E. Men Under Stress, Roy R. Grinker, Lt. Col., MC, 
Army Air Forces, and John P. Spiegel, Major, MC, 
Army Air Forces, Blakiston, Philadelphia, 1945. 
F. Psychosomatic Medicine, Edward Weiss, M. D., 
and O. Spurgeon English, M. D., W. B. Saunders Co., 
Philadelphia, 1943. 
G. Freud’s Contribution to Psychiatry, A. A. Brill, 
M. D., W. W. Norton Co., Inc., New York, 1944. 
H. The Structure and Meaning of Psychoanalysis, 
William Healy, M, D., Augusta F. Bronner, M. D., 
Anna Mae Bowers, A. B., Alfred A. Knopf, New 
York, 1946. 
I. Lectures on Psychoanalytic Psychiatry, A. A. 
Brill, M. D., Alfred A. Knopf, New York, 1946. 
J. Common Neuroses of Children and Adults, O. 
Spurgeon English, M. D., and Gerald H. J. Pearson, 
M. D., W. W, Norton and Co., Inc., New York, 1937. 
K. Principles of Dynamic Psychiatry, Jules H. Mas- 
serman, M. D., W. B. Saunders Co., Philadelphia, 1946. 
L. Psychoanalytic Therapy, Franz Alexander, M. 
D., Thomas Morton French, M. D., The Ronald Press 
Co., New York, 1946. 
M. Psychotherapy in Medical Practice, Maurice Le- 
vine, M. D. The MacMillan Co,, New York, 1946. 
N. A History of Medical Psychology, Gregory Zil- 
boorg, M. D., W, W. Norton, Inc., New York, 1941. 
O. The Neurotic Personality of Our Time, Dr. 
Karen Homey, W. W. Norton, Inc., New York, 1937. 
P. Emotional Problems of Living, Pearson and Eng- 
lish, W. W. Norton, 1945. 
Q. The Biology of Schizophrenia, R. G. Hoskins, 
M. D., W. W. Norton, 1946. 
R. Psychoanalytic Theory of Neurosis, Otto Feni- 
chel, M. D., W. W. Norton, 1945. 
S. Outline of Neuropsychiatry in Aviation Medicine, 
Army Air Forces, School of Aviation Medicine, Ran- 
dolph Field, Texas. 
T. Fundamentals of Psychiatry, Edward A. 
Strecker, M. D., J. B. Lippincott Co., Philadelphia, 1943. 
U. Outline of Neuropsychiatry in Aviation Medi- 
cine, War Department Technical Manual, TM 8-325. 
V. A Textbook of Clinical Neurology, Israel S. 
Wechsler, M. D., W. B. Saunders Co., Philadelphia, 
1943. 
W. Orientation to Psychosomatics, Major Henry A. 
Davidson, Medical Reserve, U. S. Army. 
X. Practical Clinical Psychiatry, E. A. Strecker, 
M. D., and Franklin G. Ebaugh, M. D., The Blakiston 
Co., Philadelphia, 1940. 
Y. Outline For Neuropsychiatric Examination in 
Aviation Medicine, Captain E. L, Caveny, MC, USN, 
Chief of Neuropsychiatry, U. S. Naval Hospital 
Philadelphia, Pennsylvania. 
Z. Psychiatric Experiences in World War II, Ameri- 
can Journal of Psychiatry, March 1947. 
AA. Combat Fatigue, BuMed News Letter 18 Au- 
gust 1944. 
BB. A Textbook of Psychiatry, D. K. Henderson 
and R. D. Gillespie, Oxford University Press, New 
York, New York, 1943. 
CC. Injuries of Skull, Brain, and Spinal Cord, 
Samuel Brock, Williams and Wilkins, Baltimore, 1940. 
DD. Alcoholics anonymous, Works Publishing, Inc., 
New York, 1947. 
EE. Alcohol—One Man’s Meat, Edward A. Strecker 
and Francis T. Chambers, Jr., The Macmillan Company, 
New York City, New York, 1945. 
FF. Gallinek in Journal of Mental and Nervous 
Diseases, Vol. 108, No. 4, October 1948. 
GG. BuPers Itr Pers-5212-AJA, P13-10, dated 15 
December 1944, 
HH. Sexual Behavior in the Human Male, Kinsey, 
Pomeroy, and Martin, W. B. Saunders Co., Philadelphia, 
1948. 
JOURNAL REFERENCES 
“ ‘Experimental Neurosis’ resulting from Semi-Star- 
vation in Man”—Schiele, in Psychosomatic Medicine, 
May-June 1948. 
“The Role of Motivation”—Hawley, in American 
Journal of Psychiatry, June 1948. 
“Patient-Physician Relationship in Psychotherapy”— 
Coleman, in American Journal of Psychiatry, June 
1948. 
“Psychiatric Problems of Adolescence”—Mohr, in 
Journal of the American Medical Association, 28 Au- 
gust 1948. 
“The Use of Ergotamine Compounds in the Treat- 
ment of Acute Simple Anxiety States”—Kelley, in 
American Journal of Psychiatry, April 1948. 
“Psychoses Occurring among Psychopathic Person- 
alities”—Ripley, in American Journal of Psychiatri/, 
July, 1948. 
“The Problem Soldier and the Army”—Caldwell, in 
American Journal of Psychiatry, July 1948. 
“The Infantile Personality”—Ruesch, in Phychoso- 
matic Medicine, May-June 1948. 
“Personality Types in Soldiers with Chronic Non- 
Ulcer Dyspepsia”—Rosen et al, in Psychosomatic 
Medicine, May-June 1948. 
“The Effort Syndrome and Low Back Pain”— 
Moloney, in Journal of Nervous and Mental Diseases, 
July 1948. 
“The Flight Surgeon—His Role in Student Pilot 
Training”—Cummings, in The Military Surgeon, May 
1947. 
187 AVIATION MEDICINE PRACTICE 
“Treatment of Hysterical Amnesia by Pharmacology” 
—Myerson, in New England Journal of Medicine, 29 
May 1947. 
“Emotional Problems of a Flight Surgeon with an 
Air Group”—Requarth, in Naval Medical Bulletin, 
March-April 1947. 
“Camptocormia, or the Functional Bent Back”— 
Psychosomatic Medicine, May-June 1947. 
“Psychogenesis and Psychotherapy in Ulcerative Co- 
litis”—Psychosomatic Medicine, May-June 1947. 
“Psychosomatic Medicine—Somatization Reactions” 
—Psychosomatic Medicine, March-April 1947. 
“Brief Psychotherapy in Psychosomatic Problems”— 
Psychosomatic Medicine, March-April 1947. 
“Ocular Manifestations of Psychosomatic Disorders” 
—Harrington, in Journal of the American Medical As- 
sociation, 133-669. 
“Central Angiospastic Retinopathy”—Zeligs, in Psy- 
chosomatic Medicine, March-April 1947, 
“Emotional Factors in Urticaria”—Kay win, in Psy- 
chosomatic Medicine, March-April 1947. 
“The Psychological Component in a Case of Herpes 
Simplex”—Schroeder, in Psychosomatic Medicine, Janu- 
ary-February 1947. 
“Psychosomatic Aspects of Dermographia and Pruri- 
tus”—Dengrove, in Psychosomatic Medicine, January - 
February 1947. 
“Herpes Simplex and Second Degree Burn Induced 
under Hypnosis”—American Journal of Psychiatry, 
May 1947. 
“Psychological Factors in Men with Peptic Ulcers”— 
American Journal of Psychiatry, March 1947. 
“Neuropsychiatric Manifestations during the Course 
of Malaria”—Brookes, in Archives of Neurology and 
Psychiatry, July 1947. 
188 CHAPTER 10 
AVIATION PHYSICAL STANDARDS AND 
THE GENERAL PHYSICAL EXAMINATION 
Editor’s Note.—Consult a currently corrected copy of the 
Manual of the Medical Department, U. S. Navy, for the aviation 
physical standards, because changes are made from time to time. 
The following general provisions and stand- 
ards for physical examinations are taken from 
the Manual of the Medical Department, section 
XXV, aviation: 
21137.—Object.—The object of the aviation 
examination and the instructions incident 
thereto is to select for flying duty only such 
officers and enlisted men as are physically and 
mentally qualified for such duty, and to remove 
from flying duty those who may become tem- 
porarily or permanently unfitted for such duty 
because of physical or mental defects. Physical 
qualifications shall in general conform to the 
standards prescribed in previous sections. In 
addition, properly authorized applicants for 
duty involving actual control of aircraft shall 
qualify on psychological tests described in tech- 
nical memoranda and directives issued by the 
Bureau. 
21138. CLASSIFICATION OF PERSONNEL 
REQUIRING THE EXAMINATION 
21138,1.—Aviation personnel are divided in- 
two classes: 
Class 1.—Aviation personnel engaged in ac- 
tual control of aircraft, which includes naval 
aviators, student naval aviators, naval aviation 
pilots, student naval aviation pilots, naval avia- 
tion cadets, lighter-than-air-pilots, student 
lighter-than-air-pilots, and student flight sur- 
geons. 
Class 2.—Aviation personnel not engaged in 
the actual control of aircraft, which includes 
naval aviation observers, naval aviation navi- 
gators, naval flight surgeons, combat aircrew- 
men, and other persons ordered to duty involv- 
ing flying. 
21138.2— Class 1 is considered regular flying 
personnel and shall take the complete physical 
examination for flying. For this purpose, Class 
1 is further divided into flying service groups, 
based on the age of the aviator and other 
conditions, for which special physical require- 
ments are prescribed in paragraph 21141. 
21138.3— Class 2 shall meet the standard 
physical requirements for the general service 
with such additional requirements as are pre- 
scribed in paragraph 21141.2. 
21138.4— When submitting a Standard Form 
88 (Report of Physical Examination for Fly- 
ing), flight surgeons and aviation medical ex- 
aminers shall state whether any defect noted 
is considered disqualifying. 
21138.5— The examination for flying shall be 
limited to members of the aeronautical organi- 
zation and properly authorized applicants for 
this service. Applicants shall be given a pre- 
liminary physical examination by the local 
medical and dental officers to eliminate those 
who obviously cannot meet the physical require- 
ments for aviation, 
21139 RESTRICTIONS UNTIL 
PHYSICALLY QUALIFIED 
21139.1— No person shall be assigned to duty 
involving actual flying until he has successfully 
passed the physical examination for flying pre- 
scribed herein, and, except as authorized in 
paragraph 21139.4, until official notification 
has been received from the Bureau that such 
person is physically qualified for that duty. 
21139.2— All applicants, commissioned or en- 
listed, including those in the naval aviation 
189 AVIATION MEDICINE PRACTICE 
college program for aviation training shall suc- 
cessfully pass the physical examination for 
flying. The examination must not antedate the 
application by more than six months. When 
an applicant for aviation training is not in the 
vicinity of one of the ships or stations where 
the physical examination for flying can be 
made, he shall be examined in accordance with 
the instructions governing the examination of 
candidates for commission and shall be expected 
to meet the standards set forth as acceptable 
for a commissioned officer. Before being as- 
signed to duty involving flying under training 
as a pilot, he shall be given the complete 
physical examination for flying at the station 
to which he may be attached for training. 
21139.3— Pilots of the Naval Reserve who 
apply for permission to pilot naval aircraft shall 
be subjected to the examination prescribed 
herein unless they present satisfactory evi- 
dence that they have passed such an exami- 
nation within six months of the dates on which 
flight is desired. 
21139.4— Pending receipt of the approved 
copy of the record of physical examination 
(par. 21146), or certificate from the Bureau 
that the record of the physical examination 
has been approved, personnel may be considered 
physically qualified if an authorized medical 
examiner (par. 21145) certifies that the appli- 
cant has no physical or mental defect that 
would disqualify him for flying. 
21140. POLICIES ON SERVICE GROUPS FOR 
PILOTS OF NAVAL AIRCRAFT 
21140.1—The following policies shall, in gen- 
eral, be followed in the assignment of pilots of 
naval aircraft to flight duties: 
Service group I: Pilots under 40 years of 
age. Unlimited. 
Service group II: Pilots of 40 to 50 years of 
age, or younger pilots who, for other reasons, 
are not qualified for unrestricted flying in serv- 
ice group I, but who are so qualified for unre- 
stricted flying in service group II, shall not 
be assigned to fighter, bomber, or torpedo 
squadrons. 
Service group III: Pilots over 50 years of 
age shall normally be expected to perform 
flights in executive or broad command status. 
Solo flying shall be performed in such basic 
types of naval aircraft as may be prescribed 
by the Deputy Chief of Naval Operations for 
Air, as believed commensurate with their physi- 
cal and service qualifications. 
Pilots of younger age groups who for physi- 
cal or other reasons are not qualified for un- 
restricted flying in their service group, but who 
are physically and otherwise qualified for flying 
in service group III, may be so employed when 
sufficiently justified by other considerations. 
Normally the assignment of pilots below the 
rank of captain to service group III shall be 
restricted, and shall be limited to individuals 
recovering from illness or injury or to individ- 
uals not physically qualified for other service 
groups whose flying experience and the needs 
of the service sufficiently justify their employ- 
ment in a limited pilot status. 
21140.2— The physical requirements em- 
ployed in determining the above service groups 
are provided in paragraph 21141. 
21140.3— Should any pilot fail to meet the 
physical requirements prescribed for unre- 
stricted flying in his service group, such failure 
shall be set forth in the Standard Form 88 
(Report of Physical Examination for Flying), 
and the report forwarded to the Bureau. The 
Bureau will submit its recommendation to the 
Bureau of Naval Personnel via the Deputy 
Chief of Naval Operations (Air), and the pilot 
shall be disposed of as follows: 
1. Permitted to continue unrestricted flight 
status in his Service Group subject to waiver 
of defects by the Bureau of Naval Personnel. 
2. Restricted to flight duties of the next 
service group, that is, from I to II, or from 
II to III. 
3. Restricted to flight duties of lessened 
tempo commensurate with present temporary 
physical condition (pilots recuperating from in- 
juries or illness). 
4. Restricted to flight duties of service group 
III, requiring the presence of a copilot quali- 
fied in service group I or II. 
5. Dropped from flight status. 
21141. PHYSICAL REQUIREMENTS FOR 
AVIATION PERSONNEL 
21141.1—Class I.—Aviation personnel en- 
gaged in the actual control of aircraft.— (a) 
190 Chapter 10. —AVIATION PHYSICAL STANDARDS AND EXAMINATION 
Service group I (pilots under 40 years of age, 
unrestricted flying). The physical requirements 
for these personnel shall be those set forth 
in paragraphs 21149 through 21165 below. 
Service group II (pilots 40 to 50 years of 
age, or younger pilots who for other reasons 
are not qualified for unrestricted flying in 
service group I but who are qualified for un- 
restricted flying in service group II, not to 
include fighter, bomber, or torpedo squadrons). 
Physical requirements for unrestricted flying 
in service group II shall be the same as those 
prescribed for service group I, with the follow- 
ing exceptions: 
1. Visual acuity shall be not less than 10/20 
for each eye unaided by glasses, provided that 
when visual acuity is less than 13/20 for either 
eye, it shall be corrected by lenses to 20/20 
and the correction shall be worn while flying. 
2, Variation in depth perception shall not 
exceed 35 mm. with the aid of glasses. 
3. Accommodation below the requirements 
for age is permissible, provided that ac- 
commodation for each eye shall be not less 
than 3 D without correction. Whenever accom- 
modation is less than 3 D, it shall be corrected 
to a minimum of at least 3 D by lenses, which 
correction shall be placed in the lower section 
of lens only (bifocal or lower half of lens) and 
be available for use at all times when flying. 
4, Moderate defects of hearing may be per- 
mitted, but shall not exceed the minimum of 
7/5 whispered voice, binaural. 
Service group HI (pilots over 50 years of 
age, who will normally be expected to perform 
flights in executive or broad command status). 
Physical requirements for unrestricted flying 
within service group HI shall be the same as 
for service group I, with the following excep- 
tions : 
1. Visual acuity shall be not less than 8/20 
for each eye unaided by glasses, provided that 
when visual acuity is less than 13/20 for either 
eye, it shall be corrected to 20/20 by lenses and 
the correction worn while flying. 
2. Variation in depth perception shall not 
exceed 35 mm. with the aid of glasses. 
3. There shall be no muscle imbalance 
(phoria) of sufficient degree to result in di- 
plopia within 50 cm. of the central position of 
the tangent curtain. 
4. Accommodation below the requirements 
for age is permissible, provided there shall be 
not less than 3 diopters of accommodation for 
each eye with the aid of glasses and the cor- 
rection shall be placed in the lower section of 
lens only (bifocal or lower half of lens) and 
be available for immediate use at all times 
when flying. 
5. The diastolic blood pressure shall not 
regularly exceed 100 mm. Hg. The systolic 
blood pressure shall not regularly exceed 165 
mm. Hg. 
21141,2—Class 2.—Aviation personnel not 
engaged in actual control of aircraft: (a) 
Naval aviation observers.—Candidates shall 
normally be expected to meet the standard 
physical requirements prescribed for the gen- 
eral service with the following additional re- 
quirements as prescribed for naval aviators; 
namely, accommodation of the eyes, circulatory 
efficiency, and the neuropsychiatric examina- 
tion. Reports of examinations shall be made 
on Standard Form 88, as provided in para- 
graph 21146. In each case that a Standard 
Form 88 is forwarded to the Bureau appropri- 
ate entries shall be made on the NavMed-H-9 
(Aviation Medical Abstract) of the individual’s 
health record. 
Naval aviation observers (navigation or tac- 
tical) .—Candidates shall be physically qualified 
and temperamentally adapted for duty involving 
flying in accordance with existing standards 
for candidates for flight training leading to the 
designation of naval aviator or naval aviation 
pilot, except that the ACT, MCT, and BI tests 
are not applicable, and shall not be adminis- 
tered. Reports of examination shall be made 
on Standard Form 88 as provided in para- 
graph 21146. In each case that a Standard 
Form 88 is forwarded to the Bureau appropri- 
ate entries shall be made on the individual 
NavMed-H-9 (Aviation Medical Abstract) of 
the individual’s Health Record. 
Naval aviation observers {radar).—No sne- 
cific physical standards beyond those for the 
general service shall be required. Candidates 
shall be examined physically to determine their 
fitness to engage in aerial flights, with the ex- 
amination relating primarily to the circulatory 
system, neuropsychiatric stability, and patency 
of the eustachian tubes. The purpose of such 
191 AVIATION MEDICINE PRACTICE 
an examination is to eliminate those individu- 
als with physical defects likely to be aggra- 
vated by duty involving flying, or to constitute 
a hazard when performing such duty. The 
result of the examination shall be entered on 
the NavMed-H-9 of the individual’s health 
record, and his commanding officer shall be 
notified as to his physical qualifications. No 
report of these examinations shall be made to 
the Bureau. 
Naval flight surgeons and aviation medical 
examiners.—When ordered to duty involving 
flying (not in control of aircraft), naval flight 
surgeons and aviation medical examiners shall 
meet the physical requirements prescribed for 
naval aviation observers. Reports of examina- 
tion will normally not be made to the Bureau. 
In the case of physical disqualification, how- 
ever, the report of examination shall be regu- 
larly prepared on Standard Form 88 and for- 
warded to the Bureau. When a Standard Form 
88 is forwarded to the Bureau appropriate en- 
tries shall be made on the NavMed-H-9 (Avia- 
tion Medical Abstract) of the individual’s 
Health Record. 
Student naval flight surgeons.—Physical re- 
quirements for student naval flight surgeons 
are those prescribed for qualified naval flight 
surgeons; provided that for the purpose of 
flight indoctrinal training, in order to be physi- 
cally qualified to solo elementary type aircraft, 
vision shall be not less than 15/20 in each 
eye, unaided by glasses, and depth perception 
shall not exceed 30 mm. Failure to meet the 
special requirements of the eyes shall serve 
to disqualify only for solo flying, but shall 
not disqualify for other indoctrinal training in- 
volving flying, leading to the designation of 
flight surgeon. Reports of examination will 
normally not be made to the Bureau. In the 
case of physical disqualification, however, the 
report of examination shall be regularly pre- 
pared on Standard Form 88 and forwarded to 
the Bureau. When a Standard Form 88 is for- 
warded to the Bureau appropriate entries shall 
be made on the NavMed-H-9 (Aviation Medi- 
cal Abstract) of the individual’s Health Record. 
Combat aircrew personnel.—The physical re- 
quirements for combat aircrew personnel are 
in general the same as those prescribed for the 
general service with the following additional 
special requirements: 
Height.—Maximum height shall not exceed 
72 inches (waived in the case of lighter-than- 
air aircraft machine gunners (Art. 5313(7), 
Bureau of Naval Personnel Manual). 
Weight.—Maximum weight shall not exceed 
185 pounds (waived in the case of lighter-than- 
air aircraft machine gunners (Art. 5313 (7), 
Bureau of Naval Personnel (Manual). 
Heart and lungs.—A normally functioning 
cardiorespiratory system in which the blood 
pressure does not persistently exceed 150 mm. 
Hg., systolic or 90 diastolic, is a requirement. 
The Schneider index test shall be conducted 
only in special cases when so indicated. It 
alone shall not be cause for rejection. 
Eyes.—No abnormality shall be allowed 
which will interfere with the wearing of gog- 
gles or the use of the eyes while in flight. 
Vision shall be not less than 20/20 in each eye, 
unaided by glasses. Color vision shall be as 
prescribed for the general service. Accommo- 
dation shall be not less than 3 diopters in each 
eye, unaided by glasses, as determined by use 
of the Prince rule or the Jaeger test type. 
Nose and ears.—Defects of hearing are al- 
lowable, provided such defects are not of suffi- 
cient degree as to interfere with radio per- 
ception. The eustachian tubes shall be patent. 
There shall be no evidence of manifest or latent 
disease of the middle ear or of the accessory 
sinuses of the face and head. Nasal obstruc- 
tion shall not exceed 50 percent of total venti- 
lation on either side; a distinction shall be made 
as between transitory turgescence and anatomi- 
cal deformity. 
Central nervous system.—Applicants shall be 
examined to determine their freedom from 
disease of the central nervous system, or evi- 
dence of psychic instability of sufficient nature 
and degree as to disqualify. 
Equilibrium.—Equilibrium shall be normal 
as determined by the self-balancing test. 
Speech.—Applicants shall have clear diction 
for normal spoken voice, with no impediment 
of speech which will interfere with radio com- 
munication. 
Reports of the physical examination of com- 
bat aircrewmen shall not be made to the Bureau; 
entries on the NavMed-H-9 (Aviation Medical 
192 Chapter 10. —AVIATION PHYSICAL STANDARDS AND EXAMINATION 
Abstract) of the individual’s Health Record 
will serve for this purpose. Commanding Offi- 
cers shall be officially informed concerning the 
result of the examinations. 
Other nonflying personnel.—When ordered 
to duty involving flying, for which specific 
physical requirements have not been prescribed, 
personnel shall, prior to engaging in such duties, 
be examined to determine their physical fitness 
for aerial flights. The examination shall relate 
primarily to the circulatory system, equilibrium, 
neuropsychiatric stability, patency of the eus- 
tachian tubes, with such additional considera- 
tion as the individual’s specific flying duties 
may indicate. The examination and its evalua- 
tion shall be of a practical nature. The result 
of the examination shall be entered on the 
Nav-Med-H-9 (Aviation Medical Abstract) of 
the individual’s Health Record and the com- 
manding officer officially notified. Reports of 
these examinations shall not be submitted to 
the Bureau. 
21142. REEXAMINATION FOR 
PHYSICAL INCAPACITY 
21142.1— A reexamination of any individual 
shall be made whenever considered necessary 
by the Bureau, the Deputy Chief of Naval 
Operations for Air, or by the commanding 
officer, to determine his physical fitness to 
continue flying duty or flying training. 
21142.2— Upon recommendation by the flight 
surgeon, the commanding officer may relieve 
from flying duty, or suspend the flying training 
of, any individual reported physically incapa- 
citated. When the individual is reported 
physically fit again by the flight surgeon, the 
commanding officer may authorize resumption 
of such duty or training. 
21142.3— Aviation personnel of class 1 (par. 
21138), upon reporting for duty at a new ship 
or station, or upon reporting for duty following 
absence due to serious injury or illness, or upon 
return to duty from a protracted leave of ab- 
sence, or when otherwise indicated, shall be 
given such physical examination as may be re- 
quired to determine their physical fitness to 
resume their flying duty. 
21142.4— When certified as fit for duty by a 
board of medical survey, a naval aviator or 
naval aviation pilot shall be examined by a 
board of flight surgeons as prescribed in para- 
graph 3323. 
21143.—Annual physical examination.—All 
aviation personnel engaged in duty involving 
actual control of aircraft (par. 21138.2) shall 
be required to undergo the complete physical 
examination for flying. Other aviation person- 
nel (par. 21138.3) on their prescribed annual 
physical examination shall be required to meet 
the specific physical standards for their classi- 
fication. Such examinations shall be recorded 
on Standard Form 88 in the case of those on 
duty involving actual control of aircraft. These 
Standard Form 88’s shall not be forwarded 
unless some disqualifying abnormality exists, 
but are retained in the activity and the results 
entered on NavMed-H-8’s (Medical History 
Sheets) of the Health Records. In the case of 
combat aircrewmen and personnel in class 2 
(par. 21138.3) ordered to duty involving flying, 
but not assigned particular flight duties, the 
results of their examinations shall be recorded 
in the Health Records on NavMed-H-9’s. 
21144. —Examination, where made.—Equip- 
ment and personnel for .conducting the physical 
examination for flying have been established 
aboard aircraft carriers and the large aircraft 
tenders, at fleet air bases, and within certain 
flag commands to which staff flight surgeons 
are attached; and at naval air stations, Navy 
and Marine Corps air bases, Naval Reserve 
aviation bases, and at other shore activities 
and commands within the several naval districts 
to which flight surgeons or qualified aviation 
medical examiners are attached. 
21145. —Examiners qualified.—The physical 
examination for flying shall be made only by 
medical officers who, after a special course of 
instruction, are qualified to conduct such an 
examination. The dental examination shall be 
conducted by an officer of the Dental Corps, if 
available. There are two groups of medical 
officers qualified to conduct the physical ex- 
amination for flying: flight surgeons, who have 
qualified by taking the basic course in aviation 
medicine followed by additional indoctrinal 
flight training; and aviation medical examiners, 
who have qualified by taking the basic course 
in aviation medicine but have not received in- 
doctrinal flight training. 
193 AVIATION MEDICINE PRACTICE 
21146. RECORDS 
21146.1— A record of the physical examina- 
tion for aviation duty shall be made on Standard 
Form 88. Reports on qualified personnel shall 
be forwarded in accordance with instructions 
on the form. 
21146.2— The following procedure shall be 
observed in examining and reporting upon in- 
dividuals found not physically qualified or tem- 
peramentally adapted for duty involving flying. 
Original examination of applicants for flight 
training—When, on original examination for 
flying, an applicant for flight training is found 
physically or psychologically disqualified for the 
performance of such duty, the report of ex- 
amination (Standard Form 88) shall be sub- 
mitted, via the commanding officer, in accord- 
ance with existing instructions. Abnormalities 
disclosed in the neuropsychiatric examination 
shall be included in the report of examination. 
Examination of designated personnel.—Stu- 
dent naval aviators, aviation cadets undergo- 
ing regular flight training, student aviation 
pilots, qualified naval aviators, qualified naval 
aviation pilots, and qualified navigators who, 
on physical examination for flying, are con- 
sidered not qualified for the performance of 
their flying duties shall appear before a board 
of medical examiners, of which at least one 
member shall be a flight surgeon, for the pur- 
pose of establishing the nature of their defects 
and their qualifications for performance of (1) 
duty involving flying or (2) general duty not 
involving flying. In the event the defects dis- 
closed as the result of such examination are 
considered sufficient to disqualify for the per- 
formance of general duty not involving flying, 
the examinee shall appear before a board of 
medical survey in accordance with instructions 
in part III, chapter 3, of the Manual of the 
Medical Department. 
Personnel temporarily disqualified.—These 
provisions are not intended to apply to flying 
personnel who may be disqualified for the per- 
formance of their duties because of disabilities 
considered as temporary (par. 21142). 
Commanding officers shall recommend direct- 
ly to the Chief of Naval Personnel the disen- 
rollment of any naval aviation college program 
student who fails to maintain the required 
physical standards. Such recommendations 
shall be accompanied by Standard Form 88. 
Assistance may be requested for the physical 
examinations from the Commandant of the 
naval district. 
21146.3—Naval aviators, naval aviation pi- 
lots, student naval aviators, and aviation cadets, 
on being surveyed to duty following a serious 
illness or injury, shall appear before a board 
of flight surgeons, or flight examiners, to deter- 
mine their physical and temperamental quali- 
fications for return to flight duty. Standard 
Form 88 shall accompanjr the survey to the 
Bureau (Par. 3323). 
21147. —Transfer of records.—Whenever an 
individual is transferred from one ship or sta- 
tion to another, the certified copy of his current 
Standard Form 88 shall be forwarded to the 
medical officer of his new ship or station. 
21148. —Inspection of records.—The physical 
examination records of aviation personnel in 
Class 1 (par. 21138.1) shall be inspected by 
the medical and dental officers annually at the 
end of January. If a medical or dental record 
is missing or incomplete in any particular, 
the medical or dental officers shall so inform 
the commanding officer, who shall direct the 
individual to report to the medical or dental 
officers for the necessary examination to com- 
plete his records. 
21149. THE EXAMINATION 
21149.1— Except as modified by the provi- 
sions of this paragraph, the general physical 
examination and general physical standards 
shall be the same as those prescribed for the 
general service. 
21149.2— Properly authorized applicants for 
duty involving actual control of aircraft who 
fail to attain the qualifying scores on psycho- 
logical tests as specified in technical memoranda 
and directives of the Bureau shall be disquali- 
fied and shall not proceed to the flight physical 
examination. 
21149.3— A history of any of the following 
shall be considered as disqualifying: syphilis, 
repeated attacks of hay fever or asthma, recent 
attacks of malaria, paroxysmal tachycardia, 
any organic heart disease, recurrent attacks of 
any of the rheumatic group, recent renal calcu- 
194 Chapter 10. —AVIATION PHYSICAL STANDARDS AND EXAMINATION 
lus, encephalitis lethargica, or any illness ac- 
companied by diplopia and lethargy. 
21149.4—Height and weight.— (3) The mini- 
mum height is 66 inches. The maximum height 
is 76 inches. No specific minimum weight is 
established. In general the maximum weight 
shall be 200 pounds, below the age of 40 years, 
except that applicants weighing in excess of 
200 pounds may be accepted without waiver if 
such excess weight is due to heavy bone struc- 
ture and musculature and is not due to obesity. 
Individuals shall be well proportioned. Marked 
disproportion in the physical proportions is a 
cause for rejection. 
(b) Chest.—Any condition that serves to im- 
pair respiratory function may be cause for 
rejection. The examinee, if an average-sized 
individual should normally have not less than 
three inches of chest expansion. A variation of 
one half inch is allowable if the individual is 
otherwise acceptable. 
(c) Cardiovascular system.—Cardiac arrhy- 
thmia or heart murmur or other evidence of 
cardial abnormality shall be the cause of care- 
ful study, including recourse to an electro- 
cardiographic examination when indicated. Evi- 
dence of heart disease shall be cause for rejec- 
tion. 
Blood pressure and pulse rate.—In consider- 
ing the blood pressure, the examiner must give 
due regard to the age of the candidate and to 
physiological causes such as excitement, recent 
exercise, and digestion. The condition of the 
arteries, the tenseness of the pulse, and the 
degree of accentuation of the aortic second 
sound must be taken into consideration, as 
must also the relation between the systolic and 
diastolic pressures. No examinee shall be re- 
jected as the result of a single reading. When 
the blood pressure estimation at the first exam- 
ination is regarded as abnormal, or in case of 
doubt, the procedure shall be repeated twice 
daily (in the morning and in the afternoon) 
for a sufficient number of days to enable the 
examiner to arrive at a definite In 
conducting the circulatory efficiency test 
(Schneider index), the examinee shall be af- 
forded every opportunity to relax. Loud noise, 
conversation, and other disturbing influences 
which may serve to excite or adversely affect 
the examinee, are to be avoided. The test should 
not be taken within two hours after a meal. 
Smoking, fatigue, and intercurrent infections 
will affect the score. Before taking the test, the 
subject reclines in a quiet environment for not 
less than five minutes, after which the examina- 
tion proceeds as follows: 
METHOD 
Heart rate is counted for 20 seconds. When 
two consecutive counts are the same, the 20- 
second rate is multiplied by three and recorded. 
The systolic pressure is taken by auscultation 
and recorded. Two or three readings should be 
taken to be certain. 
The subject then rises and stands for two 
minutes to allow the pulse to assume a uniform 
rate. When two consecutive 15-second counts 
are the same, multiply by four and record. This 
is the normal standing rate. 
Standing pulse minus the reclining pulse 
gives the increase on standing. 
The systolic pressure is taken as before and 
recorded. 
Timed by a stop watch, the subject steps 
upon a chair 18 x/i inches high, five times in 
15 seconds. To make this uniform, the subject 
should stand with one foot on the chair at the 
count of one. This foot remains on the chair 
and is not brought to the floor again until after 
the count of five. At each count he brings the 
other foot on the chair and at the word “down” 
replaces it on the floor. This should be timed 
accurately so that at the 15-second mark on 
the stop watch both feet are on the floor. 
Start counting the pulse immediately at the 
15-second mark on the stop watch and count 
for 15 seconds. Multiply by four and record. 
Continue to take pulse in 15-second counts 
until the rate has returned to the normal stand- 
ing rate. Note the number of seconds it takes 
for this to return and record. In computing 
this return, count from the end of the 15 sec- 
onds of exercising to the beginning, of the 
first 15-second normal standing pulse count. 
If the pulse has not returned to normal at the 
end of two minutes, record the number of beats 
above normal and discontinue counting. 
Check up points and enter final rating as 
indicated in the table. If after repeated tests 
the circulatory efficiency rating is seven or less, 
195 AVIATION MEDICINE PRACTICE 
Table for grading cardiovascular changes 
B. Pulse rate increase 
on standing 
/ ■ 
A. Reclining pulse 
rate 
—' 
0-10 
11-18 
19-26 
27-34 
35-42 
f 
N 
beats. 
beats. 
beats. 
beats. 
beats. 
Rate 
Points 
points 
points 
points 
points 
points 
50-60 
3 
3 
3 
2 
1 
0 
61-70 
3 
3 
2 
1 
0 
—1 
71-80 
2 
3 
2 
0 
—1 
—2 
81-90 
1 
2 
1 
—1 
—2 
—3 
91-100 
0 
1 
0 
—2 
—3 
—3 
101-110 
— 1 
0 
—1 
—3 
—3 
—3 
D. Pulse rate increase immediately after exercise 
C. Standing pulse 
rate 
11-20 
21-30 
31-40 
41-5(N 
/ ——— 
\ 
beats. 
beats. 
beats. 
beats. 
beats. 
Rate 
Points 
points 
points 
points 
points 
points 
60-70 
3 
3 
3 
2 
1 
0 
71-80 
3 
3 
2 
1 
0 
0 
81-90 
2 
2 
2 
1 
0 
—1 
91-100 
1 
2 
1 
0 
—1 
—2 
101-110 
1 
1 
0 
—1 
—2 
—3 
111-120 
0 
1 
—1 
—2 
—3 
—3 
121-130 
0 
0 
—2 
—3 
—3 
—3 
131-140 
—1 
0 
—3 
—3 
—3 
—3 
E. Return of pulse rate to standing normal after exercise F. Systolic pressure. 
standing. 
compared with 
reclining 
Seconds 
Points Change 
in mm. 
Points 
more . . . . 
3 
2 
1 
0 Fall of 2-5 
0 
. 
—1 
After 120: 11-30 beats 
above normal. . 
—2 
it is considered sufficient to disqualify. 
Enter history of case, including amount of 
sleep, amount of smoking, kind of work (out- 
door or indoor, active or sedentary, etc.), time 
since last meal, any personal worries, or any 
pathological condition which might affect the 
condition of the subject. 
INTERPRETATION OF FINDINGS 
Blood Pressure.—If the examinee is a candi- 
date for flight training, the systolic blood pres- 
sure shall not persistently exceed 135 mm., nor 
the diastolic pressure exceed 90 mm. In the 
case of qualified pilots, if the examinee is over 
25 years of age, the systolic blood pressure shall 
not persistently exceed 150 mm. If the exam- 
inee is 25 years of age or younger, the systolic 
pressure shall not persistently exceed 140 mm. 
A systolic blood pressure of less than 105 mm. 
disqualifies. A diastolic blood pressure persis- 
tently above 95 mm. is disqualifying. Abnor- 
mally low diastolic blood pressure should be 
viewed with concern, particularly with regard 
to its effect on vasomotor tone while flying. In 
such cases, the underlying cause should be de- 
termined if possible. The condition, if suffi- 
ciently marked, may be considered as disquali- 
fying. 
Circulatory index.—This index shall be re- 
garded as a valuable check on the physical con- 
dition of the examinee. An index below eight 
shall be regarded as unsatisfactory. No in- 
dividual shall be rejected because of a single 
failure to pass the test satisfactorily, but shall 
be recalled for further observation and study. 
When the index is persistently below the ac- 
ceptable limit and is indicative of neurocircula- 
tory asthenia, or other abnormalities of the cir- 
culatory system, the examinee shall be disquali- 
fied. 
Teeth.—Evidence of marked malocclusion, 
especially when associated with a weak or 
defective dental arch, or with evidence of ex- 
tensive caries or loss of teeth, shall be cause for 
rejection. 
Neuropsychiatrical examination.—Following 
the completion of the general examination, the 
196 Chapter 10. —AVIATION PHYSICAL STANDARDS AND EXAMINATION 
examiner shall make a careful study of the 
examinee’s family history for evidence of in- 
sanity, familiar traits of psychoneurotic mani- 
festations, degenerations, and inherited defi- 
ciencies. The candidate’s personal history shall 
be searched for significant factors which relate 
to the formative years that affect his person- 
ality trend. The infantile period shall be 
searched for evidence of retardation. Consider- 
ation shall be given to examination of the fam- 
ily life, play life, school life, sex life, and a 
careful search for epileptic equivalents. Deter- 
mine the family attitude toward flying and the 
examinee’s reaction to the stresses of life and 
his general emotional response and control. The 
object of the examination shall be to determine 
the individual’s basic stability and capacity to 
react favorably to the special stresses en- 
countered in flying. This phase of the examina- 
tion shall be performed routinely only on ap- 
plicants for flight training who are otherwise 
physically qualified. 
N eurological examination.—A careful neuro- 
logical examination shall be made, attention 
being given to the following examinations and 
report of findings: 
Pupils.—Regular, irregular, equal, unequal, 
do or do not react to light and accommodation. 
Deep sense {Romberg).—Negative, slightly 
positive or pronouncedly positive. 
Deep reflexes.—Patellar, biceps, etc.—Absent 
(o), diminished (—), normal (-f-), hyperactive 
(H—h)> and exaggerated (-j-H—h)- 
Superficial reflexes.—Abdominal, cremas- 
teric, etc.—Any abnormalities found. 
Sensory disturbances.—Any abnormalities 
found. 
Motor disturbances.—Evidence of muscle 
weakness, paresis, or any other abnormality. 
Trophic disturbances.—Evidence of atrophy, 
compensatory hypertrophies, or any other ab- 
normality. 
Tremors.—State whether fine or coarse, and 
name parts affected. 
Tics.—Specify parts affected. 
Cranial nerves.—Examine carefully for evi- 
dence of impaired function or paresis. It should 
be remembered that some of the cranial nerves 
are subject to frequent involvement in a num- 
ber of important diseases, such as syphilis, 
meningitis, encephalitis lethargica, and injuries 
to the cranium. 
Psychomotor tension.—Ability voluntarily to 
relax. This shall be tested by having the ex- 
aminee rest forearm upon palm of examiner 
and then testing the tendon reflexes of the fore- 
arm with a percussion hammer. The flight 
surgeon should keep himself informed regard- 
ing all indications of staleness in order to recog- 
nize the earliest manifestations of that condi- 
tion. 
Peripheral circulation.—Examine for flush- 
ing, mottling, and cyanosis of face, trunk and 
extremities. Question as to the presence of 
localized sweating (armpits and palm) and 
cold extremities. Any abnormalities disclosed 
on the neurological examination should be care- 
fully studied and an opinion expressed as to 
their cause and significance and whether they 
are sufficient cause for rejection. 
21149.5—After the examination has been 
completed, the examiner shall make an assess- 
ment of the individual’s qualifications for fly- 
ing, based upon the physical findings and the 
result of the neuropsychiatric examination. 
While no individual will possess all good traits, 
or all bad ones, the examiner shall summarize 
his impressions of the individual’s aeronautical 
adaptability, which shall be recorded as favor- 
able or unfavorable. When an individual is 
found to be physically qualified but his aero- 
nautical adaptability is regarded as unfavor- 
able, the entry of findings on Standard Form 
88 as finally recorded, shall be “Physically qual- 
ified but not aeronautically adapted.” When an 
individual is found not aeronautically adapted, 
sufficient comment and information shall be 
furnished to justify such a conclusion. 
21150. VISUAL ACUITY 
21150.1—Apparatus.—The apparatus for 
testing visual acuity consists of five Snellen 
test charts, each with a different arrangement 
of letters and a blank card about 6x9 cm. 
Four test charts are cut off so that the 20-foot 
and successive smaller rows of letters are used. 
The central chart is left fully exposed. The five 
charts are arranged in close formation against 
a neutral-colored wall at the end of the exam- 
ining room and each is numbered. The numerals 
197 AVIATION MEDICINE PRACTICE 
must be distinctly visible at a distance of 20 
feet. Two 100-watt daylight Mazda lamps with 
reflectors are installed about four feet above 
and in front of the test charts to provide uni- 
form illumination. A single 200-watt daylight 
Mazda lamp in a suitable reflector may be sub- 
stituted for the above. The switches controlling 
these lamps and the spotlight used with the 
phorometer trial frame should be located on 
the side wall, where they can be reached easily 
by the examiner as he stands beside the ex- 
aminee’s chair. All windows and other sources 
of light located in front and to the side of the 
examinee are shaded during the examination. 
Other standard appliances acceptable to the 
Bureau for testing visual acuity may be used 
in lieu of the apparatus described. 
21150.2— Procedure.—Upon entering the 
room, the examinee occupies a chair facing the 
test charts exactly 20 feet away. In order to 
prevent study of the letters, the test is begun 
promptly. The examiner stands at one side of 
the examinee, using the 6x9 cm. blank card 
to cover the left eye while the right is being 
tested. Designating one of the small charts by 
number, the examiner instructs the examinee 
to read as many letters as possible. When the 
best vision for the right has been obtained, 
the card is shifted to cover the right eye and 
the left eye is tested on one of the other small 
charts. The large (complete) chart is used only 
when the vision is less than 20/20. The row 
of smallest letters read correctly determines the 
numerator of the fraction used in recording 
visual acuity. The number of smaller letters 
read in the next line is added to this fraction 
following the plus sign; for example 20/20 -(- 4. 
21150.3— Precautions.—Every possible safe- 
guard is thrown around the test to prevent 
memorizing the charts. Examinees awaiting 
their visual acuity test are not permitted to re- 
main in the room within sight of the test let- 
ters or where they can hear them read aloud. 
When the examinee is suspected of having 
memorized the charts, the examiner will select 
letters in the doubtful lines and have the exam- 
inee name them. The small charts should be 
given a different arrangement from time to 
time in order to prevent memorizing the letters 
according to the position of the charts on the 
wall. One eye is completely screened from the 
letters while the other is being tested. The use 
of the hand or of an opaque disk from the trial 
case as a screen does not insure a monecular 
test. 
21150.4 — Interpretation of findings. — For 
candidates for flight training, the minimal vis- 
ual requirement for each eye is 20/20. For 
qualified and experienced pilots, visual acuity 
of not less than 15/20 for each eye unaided by 
glasses may be permitted when the pilot’s ex- 
perience is sufficient to compensate for this 
departure from normal vision. 
21151. DEPTH PERCEPTION AT SIX METERS 
21151.1— Apparatus.—Depth perception ap- 
paratus may be obtained from the Naval Medi- 
cal Supply Depot on approved requisition. The 
apparatus shall be installed in such a manner 
as to receive adequate illumination without the 
examinee being subjected to the direct glare 
of the light. 
21151.2— Procedure.—The rods in the box 
are widely separated by the examiner, and the 
examinee is required to manipulate the two 
cords so as to bring the movable rod beside 
the fixed one in such position that both appear 
to be the same distance from him. The test 
is repeated several times, the rods being widely 
separated before each trial. The examinee’s 
estimation of depth difference is read in milli- 
meters directly from the scale and entered on 
the record. The test shall be conducted at a 
distance of 20 feet. 
21151.3— Precautions.—No information con- 
cerning the results of the successive trials shall 
be given the examinee until after the test is 
completed. The examinee is required to hold 
his head straight and not to one side or the 
other. Care shall be taken by the examiner to 
avoid casting a shadow on the background, to 
avoid placing the hands so as to give the exam- 
inee information as to his error, and to avoid 
any facial expression from which the examinee 
might gain information as to the result of his 
efforts* 
21151.4 — Interpretation of findings. — An 
average depth difference of more than 30 mm. 
in five readings disqualifies. An erratic result 
shall necessitate an examination the following 
day and if still erratic shall disqualify until 
consistently below 30 mm. 
198 Chapter 10. —AVIATION PHYSICAL STANDARDS AND EXAMINATION 
21152. THE MADDOX-ROD SCREEN TEST 
AT SIX METERS 
21152.1 — Apparatus. — A photometer trial 
frame equipped with a pair of multiple Maddox 
rods and a pair of Risley rotary prisms, a 
blank card about 6x9 cm., which serves as a 
screen, and a blank card about 13 x 20 cm., 
with a 3-cm. hole in its center, shall be used. 
21152.2—Procedure.—Before beginning the 
test, determine the examinee’s fixing eye. For 
this purpose the 13 x 20 cm. card is employed. 
The examinee, seated, facing the spotlight six 
meters away, grasps the card by the long sides 
with both hands. While looking intently at the 
light, he slowly raises the card at arm’s length 
and locates the light through the hole without 
closing either eye. Only one eye can see the 
light through the hole, and the eye selected for 
this purpose is the one used habitually for 
sighting or fixing. The photometer trial frame 
is now properly leveled and adjusted closely 
in front of the examinee’s eyes. 
One of the multiple Maddox rods is swung 
into position before the non-fixing eye. A rotary 
prism is placed before the same eye. The sight- 
ing or fixing eye must have an unobstructed 
view of the spotlight. For the measurement of 
esophoria or exophoria, the Maddox rod is ad- 
justed before the nonsighting eye to give a 
vertical line of light. The rotary prism is ad- 
justed also before the nonsighting eye for the 
measurement of lateral deviation and set four 
or five prism diopters off the zero mark. This 
gives enough deflection at the first reading to 
detect an examinee who has been coached to 
say the line passed through the light. The 
6x9 cm. card is moved from one eye to the 
other a few times to ascertain if the examinee 
sees both line and the light. 
If the line is not seen readily, the Maddox 
rod is readjusted by centering it carefully in 
front of the pupil. Some further darkening 
of the room may be necessary to render.the 
rod clearly visible. When the examinee sees 
the line with one eye and the light with the 
other, the examiner holds the card or screen in 
front of the nonfixing eye to shut out the image 
of the line. The examinee now sees only the 
light. After he has fixed it for several seconds, 
the screen is removed for an instant and quickly 
replaced. In that brief interval the examinee 
will be able to see the line and locate it in ref- 
erence to the light. 
After one or two such exposures, he will say 
that the line is to the right or left of the light 
or possibly through it. He is instructed to 
grasp the milled head that rotates the prism 
and turn it to bring the line directly into the 
light. To enable him to do this, the screen is 
removed from the eye at intervals and quickly 
replaced. Finally, the examinee will have ro- 
tated the prism enough to cause the line to pass 
through the light every time the screen is re- 
moved. The number of prism diopters neces- 
sary to do this is read from the scale of the 
rotary prism. This is entered on the record as 
esophoria if the prism is base out, and exo- 
phoria if the prism is base in. 
For the measurement of hyperphoria, the 
Maddox rod before the nonfixing eye is read- 
justed to give a horizontal line of light. The 
rotary prism is also readjusted before the same 
eye to measure vertical deviation. The screen 
is used exactly as before to give an occasional 
glimpse of the line. The number of prism diop- 
ters read from the scale is recorded as right 
hyperphoria if the prism is base down before 
the right eye, or base up before the left. It 
is recorded as left hyperphoria if the prism is 
base up before the right eye or base down be- 
fore the left. In testing for hyperphoria, the 
Stevens’ frame which is normally a part of the 
phorometer mechanism, should be used instead 
of the larger prisms. The Stevens’ frame at- 
tachment is composed of weaker prisms which 
are calibrated in tenths of a diopter and there- 
fore permit more accurate readings for hyper- 
phoria. 
21152.3— Precautions.—The Maddox rod and 
the measuring prism are always used together 
before the nonfixing eye and never before the 
fixing eye. The test gives an inaccurate result 
if the examinee is permitted to see the line for 
a longer time than is allowed by the momentary 
flash exposures described above. 
21152.4— Interpretation of findings.—Eso- 
phoria of more than 4 D., if associated with a 
prism divergence of less than 4 D., disqualifies, 
199 AVIATION MEDICINE PRACTICE 
even though the red lens test shows no evidence 
of diplopia. Esophoria of more than 10 D. dis- 
qualifies even if unassociated with any other 
visual defect. Exophoria of more than 5 D. 
disqualifies. Hyperphoria of more than 1 D. 
disqualifies. 
21153. PRISM DIVERGENCE 
21153.1— Apparatus.—The phorometer trial 
frame and the rotary prism with a spotlight 
1 cm. in diameter at a distance of 13 inches 
from the eyes shall be used. 
21153.2— Procedure.—The procedure shall 
follow paragraph 2124C. 
21153.3— Interpretation of findings.—A prism 
divergence of less than 12 diopters is disquali- 
fying. An excessive amount of prism divergence 
(above 22 diopters) should be accompanied by 
a disqualifying amount of exophoria. 
21154. RED LENS TEST 
21154.1 — Apparatus. — A spectacle trial 
frame, a red lens from the trial lens case, a 
small light such as an ophthalmoscope without 
head, and metric rule or tape shall be used. 
21154.2—Procedure.—The examinee is seated 
in the darkroom facing the dark wall or tan- 
gent curtain at 75 cm. distance. The spectacle 
trial frame is adjusted into position and the 
red lens from the trial lens case is placed in 
one cell of the trial frame. With the examinee’s 
head in a fixed position, the small lamp is held 
directly before the dark tangent curtain at 75 
cm. distance from the eyes. The presence or 
absence of diplopia in this position (primary) 
is noted. The light is then slowly moved from 
the central position toward the right for a dis- 
tance of 50 cm. in the horizontal plane. In the 
same manner the light is moved in the remain- 
ing five cardinal directions, up and to the left, 
to the left, down and to the left, and down and to 
the right. The presence or absence of diplopia 
in any of these positions should be noted. 
Normally, diplopia * should not occur in any 
meridian within 50 cm. of the primary or cen- 
tral position. In the presence of diplopia, no- 
tation should be made as to whether it is 
crossed, honomomous, or vertical, and the dis- 
tance in centimeters from the central position 
that diplopia occurs should be recorded. When 
diplopia is suspected and the examinee has been 
coached to deny its presence, a prism of 3 or 
4 D. may be placed, either base up or base 
down, in one cell of the trial frame, and if 
diplopia is still denied, the statement is obvi- 
ously untrue. 
21154.3— Precautions.—The head of the ex- 
aminee must remain fixed and the movement of 
the light followed only by the eyes. No tilting 
or rotation of the face shall be permitted. 
21154.4— Interpretation of findings.—Diplo- 
pia within 50 cm, of the primary position, in 
any meridian, disqualifies. 
21155. TEST OF 
ASSOCIATED PARALLEL MOVEMENTS 
21155.1— Apparatus.—A pin with a white 
head 2 mm. in diameter shall be used. 
21155.2— Procedure.—The examinee stands 
near a window where good illumination falls on 
both eyes. The examiner holds the white headed 
pin about 33 cm, directly in front of the exami- 
nee’s eyes and directs him to look at it steadily. 
Nystagmus in the primary position is to be 
noted at this stage of the test. The examinee 
is then instructed to hold his head still and 
watch the pin as it is moved slowly to his right. 
The pin is not carried beyond the field of bin- 
ocular fixation, but is held motionless for a 
moment near the lateral limit of the field. Each 
eye is inspected to discover any failure in fix- 
ing the pin. The lagging or overaction of 
either eye is noted. The pin is then carried 
slowly to the extreme left, up and to the 
left, straight up, up and to the right, to 
the extreme right, down and to the right, 
straight down, and down and to the left. The 
lagging of either eye in any of these eight 
cardinal directions is due to underaction of at 
least one of the extrinsic ocular muscles. The 
underaction is recorded by stating which eye 
lags and in which direction the lagging is ob- 
served. In the same way any overshooting of 
either eye is recorded by stating which eye is 
involved and in which direction. If any under- 
action or overaction is revealed by this test, 
the final diagnosis shall be made on the tangent 
curtain by means of the red lens test. 
21155.3— Interpretation of findings.—The ex- 
200 Chapter 10. —AVIATION PHYSICAL STANDARDS AND EXAMINATION 
aminee is disqualified if the underaction or 
overaction of any of the extrinsic ocular mus- 
cles results in heterophoria at six meters in 
excess of normal limits, or produces diplopia 
within 50 cm. of the primary position in any 
meridian as determined by the red lens test. 
21156. INSPECTION OF THE EYES 
21156.1— Procedure.—Whenever possible, the 
eyes are inspected by bright daylight. Every 
pathologic condition and congential anomaly is 
recorded. The following conditions may be 
found by this procedure: 
1. Lids: Ptosis, blepharitis, trichiasis, en- 
tropion, ectropion, and chalazion. 
2. Tear Sacs: Imperfect drainage. 
3. Lower Puncta: Failure of contact with 
bulbar conjunctivae. 
4. Conjunctivae: Trachoma and old scars. 
5. Corneas: Scars, pannus, and pterygium. 
6. Pupils : Unequal size, irregular shape, and 
failure to react to light or accommodation. 
21156.2 — Interpretation of findings. — Any 
pathologic condition which may become worse 
or interfere with the proper functioning of the 
eyes under the fatigue and exposure of flying 
disqualifies. 
21157. TEST FOR ACCOMMODATION 
21157.1— Apparatus.—The Prince rule, a 
small millimeter rule, and a card with several 
rows of small letters shall be used. 
21157.2 — Procedure. — Accommodation is 
measured from the anterior focus of the eye, 
which is about 11.5 mm. in front of the cornea. 
Using the millimeter rule, make a pencil mark 
on each side of the examinee’s nose 11.5 mm. 
in front of the right and left cornea respective- 
ly. In measuring the accommodation of the 
right eye, lay the flat side of the Prince rule 
against the right side of the examinee’s nose, 
with the end of the rule at the pencil mark. The 
rule is held horizontally and extends directly 
to the front, edge up. The card of test letters 
is held not more than 5 cm, in front of the 
examinee’s right eye. His left is screened from 
sight of the letters by the flat side of the rule. 
The card of test letters is now carried slowly 
away from the eye and the examinee instructed 
to begin reading the letters aloud as soon as 
they become legible. The card is halted the in- 
stant he begins to read the letters correctly and 
the point on the rule opposite the card is read 
off in diopters. This is the measure of accom- 
modation of the right eye. To test the left eye, 
change the rule to the left side of the nose and 
repeat the above procedure, using a different 
line of letters. 
21157.3 — Precautions. — The examinee is 
placed with his back to good light, with the 
card well illuminated. The card is started from 
close to the eyes and carried away from them. 
The letters on the test card are read aloud. The 
same line of letters is not used for testing both 
eyes. 
21157.4—Interpretation of findings.—The 
following table gives the mean values of ac- 
commodation in diopters from 18 to 50 years of 
age. Accommodation may be regarded as with- 
in normal limits provided it is not more than 
3 D. below the mean for the examinee’s age. 
The examinee is disqualified if his accommo- 
dation falls more than 3 D. below the mean for 
his age, but before an examinee is disqualified, 
his accommodation shall be taken on three suc- 
cessive days and an average of the three find- 
ings determined. Accommodation may be af- 
fected by fatigue, staleness, or other debilitat- 
ing conditions. 
Age 
Diopters 
Age 
Diopters 
Age 
Diopters 
Age 
Diopters 
18 
11.9 
24 
10.4 
30 
8.9 
36 
7.1 
19 
11.7 
25 
10.2 
31 
8.6 
37 
6.8 
20 
11.5 
26 
9.9 
32 
8.3 
38 
6.5 
21 
11.2 
27 
9.6 
33 
8.0 
39 
6.2 
22 
10.9 
28 
9.4 
34 
7.7 
40 
5.9 
23 
10.6 
29 
9.2 
35 
7.3 
45 
50 
3.7 
2.0 
21158. ANGLE OF CONVERGENCE 
21158.1—Near 'point of convergence (PcB), 
—The Prince rule and a pin with a white head 
2 mm. in diameter shall be used. The distance 
to the near point of convergence is computed 
from the base line connecting the centers of 
rotation of the eyes. The end of the Prince rule 
is placed, edge up, at the mark on the right 
side of the nose, 11.5 mm. in front of the 
cornea. The white-headed pin is held 33 cm. 
201 AVIATION MEDICINE PRACTICE 
away in the median line above the edge of the 
rule and the examinee is instructed to look at 
it intently. If both eyes are seen to converge 
upon the pin, it is then carried in the median 
line, along the edge of the rule, toward the 
root of the nose. The examinee’s eyes are care- 
fully watched and the instant one is observed 
to swing outward the limit of convergence has 
been reached. The point on the rule opposite 
the pin is then read in millimeters. This test 
is repeated until a fairly constant reading is 
obtained. To this reading 25 mm. is added, 
which will give approximately the distance 
from the near point of convergence to the base 
line, PcB. Both eyes must converge upon the 
pin at the start of the test. The examinee’s 
observation of the onset of diplopia is not relied 
upon to determine the near point, although he 
is asked to state when he sees double. The near 
point of convergence, unlike the near point of 
accommodation, varies little with age. Its 
measurement is of value only in computing the 
angle of convergence. Examinees are not quali- 
fied or disqualified on this measurement, but 
on the angle of convergence. 
21158.2— Interpupillary distance (Pd).—A 
small millimeter rule is used. The examiner 
stands with his back to the light, face to face 
with the examinee. The rule is held in the ex- 
aminer’s right hand and laid across the exam- 
inee’s nose in line with his pupils, as close to 
the two eyes as possible. The examiner closes 
his right eye and instructs the examinee to fix 
his eyes on the open left eye. With the eyes 
in this position, a predetermined mark on the 
rule is placed in line with the nasal border of 
the examinee’s right pupil. The rule must 
be held steadily in this position while the ex- 
aminer opens his right eye and closes his left. 
The examinee is then instructed to look at the 
open right eye. The point on the rule in line 
with the temporal border of the examinee’s 
left pupil is read in millimeters and the exact 
difference in millimeters between the two points 
on the rule is the interpupillary distance. 
21158.3— Computing the angle of conver- 
gence.—The following formula is used for com- 
puting the angle of convergence: 
a i * i/2PdX100 Q 
Angle of convergence = — - + 3 
An angle of convergence of less than 40° is 
undesirable, but is not disqualifying unless as- 
sociated with excessive exophoria, or diplopia 
on the tangent curtain. Diplopia in the extreme 
positions on the tangent curtain shall not be 
considered disqualifying. 
21159.—Central color vision.—Color vision 
shall be tested by means of the American Opti- 
cal Company Pseudo-Isochromatic Plates for 
Testing Color Perception, 1940. The examinee 
is placed with his back to good light (natural 
light is preferable) in such a manner as to 
insure that the plates of the chart are illumin- 
ated and free of shadow. The plates are ex- 
posed to the examinee, who is required to call 
the numbers or letters indicated in the colored 
chart. The examinee may be permitted to tilt 
or alter the position of the charts to improve 
the light. The instructions in the A. 0. C. 
chart book shall be followed, and the require- 
ments of paragraph 2125.3 as modified by Bu- 
Med Circular Letter No. 46-177 shall apply. 
21160. FIELD OF VISION 
21160.1— The examiner faces the examinee at 
a distance of 2 feet. He instructs the examinee 
to close his left eye and to fix his right eye 
on the examiner’s left eye, the examiner’s right 
eye being closed. The examiner then brings 
his moving fingers in from the periphery mid- 
way between them. The examinee is instructed 
to say when he sees the fingers, and how many. 
He should see them as soon as the examiner, 
if normal. The fingers are brought in from all 
cardinal directions. The test is then repeated 
for the left eye. Any evidence of abnormality 
should be given detailed study on the peri- 
meter. 
21160.2— The field of vision for each eye 
shall be normal as determined by the finger 
fixation test. When there is evidence of ab- 
normal contraction of the field of vision in 
either eye, the examinee shall be subjected to 
perimetric study for form and color. Any con- 
traction of the form field of 15° or more in 
any meridian shall disqualify. 
21161. REFRACTION 
21161.1—Refraction of the eyes shall not be 
required on original or routine examination, 
202 Chapter 10. —AVIATION PHYSICAL STANDARDS AND EXAMINATION 
but shall be performed in special cases only, 
when so indicated. An electric retinoscope, or 
a plain retinoscope and a wall lamp, a trial 
case and trial frame, Snellen test type, and a 
cycloplegic shall be used. 
21161.2— The tension of both eyes must be 
taken by palpation and found normal before in- 
stilling a cycloplegic. The fundus of both eyes 
must also be examined with the ophthalmo- 
scope, and if evidence of glaucoma are found 
a cycloplegic shall not be used. One drop of 
a 4 percent homatropine solution is placed in 
each eye every 10 minutes until four instilla- 
tions have been made. At the end of one hour 
from the time of the first instillation, the ex- 
aminee is ready for refraction. Retinoscopic 
examination is conducted in the darkroom and 
the results of the refraction are then verified 
by having the examinee read the Snellen charts. 
The minimum correction required to enable 
the examinee to read 20/20 each eye is re- 
corded, together with the true correction as 
determined by retinoscopy. 
21161.3— The examinee is disqualified if he 
requires more than 2 D. total correction in 
any meridian in order to read 20/20 each eye 
with the accommodation paralyzed. Of this 
allowable correction not more than a total of 
0.5 D. shall be due to any form of myopia or 
astigmatism or any combination thereof. 
21161.4— After the use of a cycloplegic the 
examinee must wear dark glasses until the 
effects have disappeared. The instillation into 
each eye of a 1 percent solution of pilocarpine 
hydrochloride in distilled water will contract 
the pupil and thus relieve the photophobia. 
21162. OPHTHALMOSCOPIC EXAMINATION 
21162.1— The examination shall not be re- 
quired on original or routine examination, but 
shall be performed in special cases only, when 
so indicated. The examination must not be made 
before the refraction is completed. In exam- 
ining the macular region of the retina, the 
light should be reduced and the exposure made 
as brief as possible. 
21162.2— Any abnormality disclosed on oph- 
thalmoscopic examination that materially in- 
terferes with normal ocular function disquali- 
fies. Other abnormal disclosures indicative of 
disease, other than those directly affecting the 
eyes, shall be considered with regard to the 
importance of those conditions. 
21163. EAR 
21163.1— General.—The external auditory 
canals and membranae tympani are examined 
by means of a speculum and good light. Wax 
interfering with a good view of the tympanum 
must be removed from the external auditory 
canal. If internal to the bend of the canal; 
the canal should be filled with a bland oil and 
blocked with cotton. The following day thor- 
ough washing of the external canal with a 
solution of sodium bicarbonate will remove the 
wax. The external canal is then examined 
throughout. Any serious permanent blocking 
of the canal or diseased condition which threat- 
ens trouble later, such as the impairment of 
hearing, disqualifies. The membranae tympani 
are then examined. A perforation or evidence 
of present inflammation disqualifies. The pres- 
ence of a small scar, caused by trouble several 
years previously which has not recurred and 
with which there is no deficiency of hearing 
and no evidence of other inflammation, does not 
disqualify. Marked retraction of a drum mem- 
brane, following chronic ear disease, disquali- 
fies. 
21163.2— Hearing tests.—Hearing should be 
normal for each ear. To determine this the 
following tests shall be used. A quiet room is 
essential. 
Whispered-voice test.—The examinee should 
stand 15 feet from the examiner with the ear 
being tested turned toward him, the other ear 
being covered or closed. The examiner, after 
full expiration, will whisper a number or word 
and require the examinee to repeat it after 
him. Each ear shall be tested in turn. If the 
examinee is unable to hear at 15 feet, the ex- 
aminer shall approach until he is able to distin- 
guish the words or numbers the distance being 
recorded in feet with 15 as the denominator. 
Clock test.—The clock test should be made 
using the standard ward desk clock, Stock No. 
7-754-700, Catalog of Navy Material, BuMed 
Section according to the instructions of para- 
graph 2130. The distance in inches at which 
the clock is heard by the examinee, with eyes 
203 AVIATION MEDICINE PRACTICE 
closed and opposite ear occluded, is taken as 
the numerator and the distance the clock should 
be heard as the denominator. Hearing by this 
test should be equivalent to 40/40. 
Coin-click test.—An assistant closes the ear 
not under examination. The examiner, 20 feet 
back of the examinee, then clicks two coins 
softly together and the examinee is directed to 
count, aloud, the number of clicks each time. 
The other ear shall then be tested in a similar 
manner. If the candidate is unable to hear the 
click, the examiner will approach until he does 
hear, the distance being recorded in feet. Hear- 
ing by this test should be equivalent to 20/20. 
21163.3—If the examiner is convinced from 
the results of the several tests that definite im- 
pairment of hearing exists, he shall reject the 
examinee if he is an applicant for aviation 
training. In case of a qualified flyer, however, 
due allowance shall be made. 
21164. NASO-PHARYNX 
In the examination of the naso-pharynx the 
examiner shall, in general, be guided by the 
instructions and requirements prescribed for 
the general service as outlined in paragraphs 
2148 and 2149 of this chapter. Any abnormality 
disclosed on examination indicating an esti- 
mated 50 percent or more of nasal obstruction, 
acute or chronic sinusitis, acute or chrome 
tonsillitis, nasal blockage, mechanical obstruc- 
tion to drainage of accessory sinuses, occlusion 
of one or both eustachian tubes, or other ab- 
normalities which may seriously interfere with 
normal function, shall be cause for rejection. 
21165. EQUILIBRIUM (VESTIBULAR) TESTS 
21165.1—Barany chair test.—The nystagmus 
and falling after turning are tested, when prac- 
ticable, on original examination and when 
otherwise indicated. Where facilities are not 
available, or circumstances do not permit of 
the test, then the examination shall be limited 
to the self-balancing test as outlined below. 
Inasmuch as the self-balancing test is in effect 
a modified Romberg test, all examinees shall 
undergo that test as a regular part of their 
examination. 
21165.2— Nystagmus.—Examinee’s head is 
inclined 30° forward, so that the tragus of the 
ear is on a horizontal line with the external 
canthus of the eye. The examinee is then 
asked to fix his eyes on a distant point and the 
chair turned slowly from side to side in order 
to note whether or not spontaneous nystagmus 
is present. Then turn the examinee to the 
right, with eyes closed, 10 times in exactly 20 
seconds. The instant the chair is stopped, click 
the stop watch; the examinee opens his eyes 
and looks straight ahead at some distant point. 
There should occur a horizontal nystagmus to 
the left of 26 second duration. A variation of 
10 seconds above or 12 seconds below is allow- 
able. 
21165.3— Falling.—The examinee’s head is 
inclined 90° forward, resting his forehead on 
his upper fist, his fists being placed one above 
the other on his knees, which are brought close 
together. He should then be turned to the 
right, five times in 10 seconds. On stopping, 
the examinee raises his head and should fall 
to the right. This tests the vertical semicircular 
canals. The examinee should then be turned 
to the left, his head forward 90°; on stopping, 
he raises his head and should fall to the left. 
21165.4— Self-balancing test.—The applicant 
stands erect, without shoes, with heels and 
large toes touching. He then flexes one knee 
to a right angle, being careful not to support 
it against the other leg, closes his eyes, and 
endeavors to maintain this position for 15 
seconds. The test is then repeated on the 
other foot. The findings are recorded as Steady, 
Fairly Steady, Unsteady, or Failed. The appli- 
cant should be instructed that this is the equi- 
librium test. There is no objection to his as- 
sisting his balance by moving and bending back 
and forth, 
21165.5— Interpretation of findings.—Inabil- 
ity to pass the tests for equilibrium satisfac- 
torily shall be cause for rejection. 
204 CHAPTER 11 
AVIATION DENTISTRY * 
Aerodontalgia is the term applied to dental 
pain resulting from a decrease in atmospheric 
pressure. 
In dealing with pain, it is necessary to dis- 
cuss the part responsible for its action, namely, 
the dental pulp. The dental pulp may be defined 
as the connective tissue occupying the central 
cavity of a tooth. It is composed of embryonal 
connective tissue which is more closely related 
to the tissues occupying the spaces of cancel- 
lous bone than to any other tissue. So we have 
as the structural elements of the dental pulp the 
odontoblasts, connective-tissue cells, intercellu- 
lar substance, blood vessels, nerves, and lym- 
phatic vessels. 
Pain registering on the teeth is carried to 
the brain by the fifth cranial nerve. All of the 
maxillary teeth are supplied by the second or 
superior maxillary division of this trigeminal 
nerve, which further branches into the poster- 
ior superior dental, middle superior dental and 
anterior superior dental nerves. The mandibu- 
lar teeth are supplied by the third or mandibu- 
lar division. 
The functions of the pulp are the formation 
of dentin, the main bulk of a tooth—in the 
embryonic developmental stage—the reproduc- 
tion of a limited amount of dentinal material 
for the protection of the pulp in various de- 
structive conditions such as dental caries, and 
sensory function responding to thermal and 
chemical change and traumatic irritation. 
The sensory function of the pulp resembles 
an internal organ in that in its normal condi- 
tion it is always inclosed in the cavity of a 
tooth. If a situation could be created where by 
only the pulps of the teeth on one side of the 
median line of both the maxillary and mandibu- 
lar arch were exposed and a stimulus applied 
to the pulp of one tooth, it would be impossible 
for the patient to say which pulp had been 
touched. This creates a difficult problem in 
diagnosis, particularly in conditions where 
there may be complications between the maxil- 
lary teeth and the maxillary sinus, as in locat- 
ing the tooth producing the pain when it is not 
clinically obvious. 
The pulp is an extremely vascular tissue and 
the arrangement of the vessels, the structure 
of their walls, and the nature of the intercel- 
lular substance through which they run render 
the tissue especially susceptible to the patho- 
logical conditions associated with alterations 
in the circulation. This is due primarily to the 
very minute foramina in the apex of a tooth. 
In other parts of the body, when damage has 
occured there is always some room for the 
tissues to swell and make room for increased 
flow of the repair vessels, but in a tooth all 
repair is limited to the size of the apical fora- 
men which is a calcified structure not amen- 
able to any pathologic condition. Therefore, 
any traumatic pressure sufficient to cause swell- 
ing or severance of the vessels in the apex of 
the tooth will cause the tissue to die. 
Although, many of these chronic devitilized. 
teeth are painless at sea level barometric pres- 
sure they will liberate gas and cause pain at low 
pressure. 
Other causes of aerodontalgia have been at- 
tributed to: carious teeth; recently filled teeth; 
teeth filled with insufficient insulating base ma- 
terial when in close proximity to the pulp. 
Radiographic examination will reveal many of 
these potential causes to the dental officer. 
As stated above, because of the relation of 
the maxillary teeth to the maxillary sinus, in 
* Prepared by Cdr. E. E. Jeansonne, D.C., USN. 
205 AVIATION MEDICINE PRACTICE 
some cases the apices of the posterior teeth ex- 
tend the floor of the sinus upward and there can 
be doubt as to where the pain and infection 
is located. 
Cases of aerotitis media have been attributed 
to abnormalities of the temporo-mandibular 
joint. These conditions, such as impaired hear- 
ing, stuffy sensation, and dull pain in the ears 
have been attributed to a loss of intermaxillary 
distance or over closure of the mandible. The 
posterior teeth and the muscles of mastication 
maintain the normal distance, but where there 
has been a loss of teeth or loss of tooth struc- 
ture from excessive wear or malocclusion the 
intermaxillary distance is changed. This will 
produce some change in the position between 
the condyle of the mandible and the glenoid 
fossa of the temporal bone. Usually the condyle 
moves upward and backward, possibly causing 
pain from pressure on the auriculo temporal 
nerve. 
Loss of maxillary distance may cause com- 
pression of the eustachian tubes by relaxation 
of the external pterygoid muscle producing 
excessive tissue in the region of the tubes. 
Costen has stated, “when this is done manually 
the tensor veli palatine muscle bordering the 
membranous anterior edge of the eustachian 
tube and the adjacent sphinomeniscus muscle 
are seen to wrinkle and crowd the eustachian 
tube, closing it firmly. During the act of swal- 
lowing the tensor veli palatini muscle should 
be tense and effect a temporary opening to the 
tube. This function cannot occur during over- 
closure and the result is derangement of intra- 
tympanic pressure”. 
A study of aviators with overclosure cases 
with correction by prosthetic interdental splint 
was made by Lowery at N.A.S., Pensacola in 
1939. The statistics of his report of 540 avia- 
tors showed that 83, or 15 percent, had loss of 
vertical dimension. Thirty-three, or 39 percent 
of the 83 persons with loss of vertical dimension 
gave histories of faulty ventilation of the tym- 
panum. This was 6 percent of the 540 exam- 
ined. The 33 cases with loss of vertical dimen- 
sion gave symptoms of discomfort and inability 
to readily equalize pressure on the tympanum, 
pain tinnitis and impaired hearing. Splints to 
lengthen the vertical dimension were construct- 
ed for 31 of the 33 cases, two did not wish 
them. After becoming accustomed to wearing 
them they were used in actual flight from six 
months to one year. Twenty-six persons sub- 
mitted written reports on the effectiveness of 
the splints, five made no reports. The reports 
showed nine persons, or 34 percent, relieved of 
all distressing ear symptoms, 14 persons or 53 
percent benefited by its use, three derived no 
beneficial results. 
An observation made on “Toothache and the 
Aviator” at N.A.S., San Diego by Joseph 
and others over a period of six months revealed 
an incidence of toothache in 1.2 percent of 
cases. They found that tooth pains had no 
particular relationship to specific altitude, be- 
yond the fact that the greatest number of pain 
reactions occurred at the highest altitude 
reached. Fifty-seven percent of cases exper- 
ienced pain at 28,000 feet, 23 percent at 18,000 
feet and the remaining twenty percent at 10,- 
000 feet or below. About half of the men re- 
ported their toothache as a sharp pain, while 
the other half complained of a dull ache. 
BIBLIOGRAPHY 
Dental Histiligy and Embryology—Noyes, F. B. 
A Syndrome of Ear and Sinus Symptoms Dependent 
upon Disturbed Functions of the Temporomandibular 
Joint—Ann, Otol, Rhin and Laryng. 43:1 (March) 
1934—Costen, J. B. 
“Loss of Intermaxillary Distance: Effect on Avia- 
tors and Relief by Interdental Splint,” U. S. Nav. Med. 
Bui. 37:367-380 (July) 1939—Lowery, R. A. 
Toothache and the Aviator—Joseph, T. V.; Cell, C. F.; 
Carr, R. M.; Shelesnyak, M. C. 
“Experimental Investigation of the Referred Pain 
of Aerodontalgia”—Journal of Dental Research. Febru- 
ary, 1947—Hutchins, H. C.; Reynolds, O. E. 
QUESTIONS 
1. Name the structural elements of the dental pulp. 
2. Why does the dental pulp fail to recover under- 
most pathologic conditions? 
3. Describe the effect caused by overclosure of the 
mandible at low pressure. 
4. What is the percentage incidence of aerodont- 
algia? 
DENTAL STANDARDS 
Summarized from BuMed Circular 
Letter No. 48-131, 23 November 1948, are given below: 
Standards for enlistment and reenlistment in the 
regular Navy and class V-(i Naval Reserve: 
206 Chapter II. —AVIATION DENTISTRY 
Applicants must be well nourished and have good 
musculature, be free from gross dental infections and 
have a minimum requirement of an endentulous upper 
and/or an edentulous lower jaw corrected or correctible 
by a full denture or dentures. 
Standards for qualification for appointment as com- 
missioned and warrant officer, USN and USNR, = 
Manual of the Medical Department U. S. Navy para- 
graph 2150.2 (formerly standards for enlistment) and 
paragraph 2151: 
Applicant must have a minimum of 18 vital, service- 
able, permanent teeth and must have sufficient teeth in 
functional occlusion to insure satisfactory incision and 
mastication. 
The applicant must not require immediate dental 
prosthesis. 
Since a change in status from enlisted to officer 
grade is an appointment and not a promotion, medical 
examining boards may not find candidates physically 
qualified on the basis of ability to perform the duties 
of the grade for which examined when requirements 
for commission are not met. It is proper, however; 
for boards to certify that the candidate’s inability to 
meet the required dental standards is not sufficient to 
disqualify, and to recommend him for appointment, 
when the candidate, in the opinion of the board, has 
other qualifications which are notably higher than aver- 
age (Secs. 864 and 867, Naval Courts and Boards). 
Standards to qualify for appointment as midship- 
man, USN, for the U. S. Naval Academy, midshipman 
and contract student U. S. Naval Reserve Officers 
Training Corps, midshipman Merchant Marine Acad- 
emy, and other officer training programs: paragraph 
2152.2 Manual of the Medical Department, U. S. Navy; 
A candidate for appointment as midshipman must 
have a minimum of 20 vital, serviceable, permanent 
teeth including (a) 4 molars. Of this number, 1 upper 
and 1 lower molar on the right side, and 1 upper and 1 
lower molar on the left side must be in functional oc- 
clusion; (b) 4 incisors. Of this number, 2 should be in 
the maxillae and 2 should be in the mandible in such 
position as to enable the applicant to incise satisfac- 
torily. The teeth must be free from dental caries, 
restorations must be of high quality, and the peridental 
tissues must be free from disease. A candidate should 
not be acceptable who has teeth missing in the anterior 
part of the mouth which have not been replaced and 
which result in an unsightly space. Any deviation 
from normal occlusion should be minor, and good func- 
tional occlusion as well as absence of interference with 
speech must be demonstrable. Candidates should not 
be considered qualified for appointment when orthodon- 
tic appliances are attached to teeth for the purpose 
of continued treatment. Orthodontic retaining appli- 
ances such as are used after the completion of treat- 
ment are acceptable provided they are not an oral 
health hazard. 
Standards for enlistment or reenlistment in the 
Marine Corps—paragraph 2150 Manual of Medical De- 
partment, U. S. Navy: 
The teeth and mouth shall be examined by a dental 
officer, if one is available. 
To be accepted for enlistment an applicant must have 
a minimum of 18 vital, serviceable, permanent teeth 
and must have sufficient teeth in functional occlusion 
to insure satisfactory incision and mastication. The 
applicant must not require immediate dental prosthesis. 
In order to be accepted for enlisted as a bugler, 
trumpeter, or musician playing a wind instrument, an 
applicant, as well as meeting the standards in 2150.2 
must have, in serviceable condition, the six upper and 
the six lower anterior teeth; namely, right and left 
central incisors, right and left lateral incisors, and 
right and left cuspids, none of which may be markedly 
out of alignment or rotated sufficiently to present 
other than a labial surface of the lip. 
The explanation of standards in paragraph 2153 
shall apply in interpreting the above requirements. 
General Examination for Aviation; Instructions and 
Requirements. Paragraph 21149.4 (e) Manual of the 
Medical Department, U. S. Navy: 
Candidates shall conform to the following standards: 
Teeth.—Evidence of marked malocclusion, especially 
when associated with a weak or defective dental arch, 
or with evidence of extensive caries or loss of teeth, 
shall be cause for rejection. 
207 CHAPTER 12 
OPERATIONAL PROBLEMS IN AVIATION MEDICINE * 
This chapter deals with problems encountered 
by the flight surgeon in aviation operational 
activities. The solution to these problems is 
characterized by the necessity of close liaison 
between the flight surgeon and the aviator. 
Discussed in this chapter are the following 
subjects: (1) air-sea rescue and survival, (2) 
air transportation of patients, and (3) aviation 
safety. 
AIR-SEA RESCUE AND SURVIVAL 
RESCUE ORGANIZATION 
Mission of an Air Sea Rescue Organization.— 
The primary mission of air-sea rescue is to 
render emergency assistance to aircraft and 
vessels in distress and to rescue survivors 
thereof. It includes assistance and rescue oper- 
ations, distress communication procedures and 
distress flight control, survival methods and 
equipment, and the indoctrination of personnel 
in these matters. 
Corollary missions are: 
1. To save manpower valuable to the mili- 
tary services. The rescue of one highly trained 
airman saves not only his life, but also the 
time and expense required for his replacement. 
2. To improve the morale of airmen and 
seamen. Nervous tension decreases consider- 
ably when airmen feel that should they be 
forced down at sea, there is a maximum chance 
of their being rescued. 
3. To relieve training and operational units 
of such search and rescue operations as may 
interfere with or divert them from their pri- 
mary missions. 
Necessity for Organized Operations.—Where 
over-water flying is limited in amount and local- 
ized in nature, it is generally true that locally 
furnished rescue facilities are adequate. If 
the volume and extent of over-water aircraft 
operations increase in a particular area the 
need for an organized air sea rescue service 
becomes imperative. In those areas where air 
sea rescue organizations are established statis- 
tics show a considerable increase in the per- 
centage of lives saved. 
Elements of Operational Organization.—Air- 
sea rescue organizations established by the 
Army and Navy vary in detail but all have the 
common element of centralized control. How- 
ever, for purposes of illustration, the basic ele- 
ments of a typical air-sea resuce organization 
are outlined: 
Rescue Operations Center: 
To centralize information 
To exercise emergency flight control when 
necessary 
To direct primary rescue facilities 
To coordinate secondary rescue facilities. 
Communication Net; 
To receive and relay distress and crash 
information 
To expedite and direct rescue operations 
To establish position of aircraft or vessels 
in distress 
To facilitate emergency flight control. 
Rescue Craft, Surface and Air, including — 
Primary facilities — established and main- 
tained for the primary purposes of engag- 
ing in rescue operations. Secondary facili- 
ties — any other units which may be 
available for air-sea rescue as an inci- 
dental mission. 
Rescue operations center.—A rescue opera- 
tions center may be any office where distress 
information is pooled, communications are 
handled, and rescue operations are directed. 
It is land-based where practicable, but in ocean 
* Prepared by Cdr, M. T. Martin. (MC), USN. 
208 Chapter 12. — OPERATIONAL PROBLEMS IN AVIATION MEDICINE 
DIAGRAM OF IDEAL AIR SEA RESCUE OPERATIONAL ORGANIZATION 
Army - Navy 
Commands 
OPERATIONS CENTER 
i 
Operations - 
Surface 
Control 
Air 
Control 
Rescue 
Control 
Weather 
Central 
Land Lines 
Direction Finders 
Radar Nets 
Communications 
Land Lines 
Base Radio 
Command Wires 
Command Radio 
Rescue Craft- 
Secondary 
Rescue 
Craft 
(Surface) 
1. Fleet 
Units 
2. Patrol 
Vessels 
3. Merchant 
Ships 
Secondary 
Rescue 
Craft (Air) 
1. Local 
Crash 
Facili- 
ties 
2. Transient 
Aircraft 
Primary 
Rescue 
Craft (Air 
and Surface) 
1. Planes 
2. Vessels 
3. Blimps 
areas may be on board a ship underway. Gen- 
erally, rescue operations can be run best from 
an existing centralized command or operations 
center having adequate communication facili- 
ties. That is, a rescue operations center should 
be an integral part of an organization having 
full knowledge of all air and surface operations 
in the area. 
Air control maintains a current record of 
aircraft in flight throughout the area for tacti- 
cal reasons and for purposes of instituting res- 
cue proceedings promptly where an aircraft is 
overdue, and diverting aircraft which may 
be of possible assistance in an emergency. 
Air control, when required, exercises emer- 
gency flight control of aircraft lost or potenti- 
ally distressed, utilizing all available radar and 
direction finder facilities. 
Surface control maintains a current. record 
of all surface ships and submarines operating 
in the area. This plot is to provide immediate 
information on locations of vessels which may 
be of assistance in rescue operations. 
Rescue control should be close to air control, 
preferably part of the same office. If rescue 
control cannot be incorporated within air con- 
trol, rapid intercommunication between the 
offices is provided. Rescue control should: 
Maintain a location and availability board 
showing all primary and secondary rescue fa- 
cilities. 
Receive and evaluate all distress informa- 
tion and take positive action toward rendering 
assistance. 
Plot the position of all distress incidents and 
the tracks of all assisting planes and vessels. 
Direct and coordinate search and rescue 
operations. 
Keep posted on weather and sea conditions 
and other factors affecting rescue. 
Communication nets.—Air Control keeps 
complete and adequate communication lines 
with all military and civil air fields in the 
area, for rapid transmission of flight plans 
and distress information. This circuit usually 
consists of teletype command telephone, CAA 
209 AVIATION MEDICINE PRACTICE 
inter-com, and radio. Air control has cogni- 
zance over all direction finder and radar net- 
works, including coverage on medium and high 
frequencies, VHF, and radar. 
Surface Control should have direct telephone- 
teletype connections with all surface operating 
bases in the area, as well as a base radio for 
communication with vessels at sea. 
Rescue control must have direct communi- 
cations, preferably telephone, with all rescue 
craft at their bases, for standby purposes; also 
a command radio for controlling rescue craft 
in activated status, and for coordinating rescue 
operations. 
Rescue craft.—Primary rescue craft are spe- 
cially equipped air and surface craft, main- 
tained in constant readiness, on full-time air- 
sea rescue duty. Lighter-than-air craft are also 
specifically designated for rescue purposes. 
Other vessels may be specifically detailed and 
assigned to air-sea rescue. 
Secondary rescue facilities may be: Local 
air base, ready planes, and crash boats; Tran- 
sient aircraft suitable for rescue missions; fleet 
units; patrol vessels; and merchant ships and 
private vessels. 
Rescue crcaft designated as primary facili- 
ties are deployed throughout the area to pro- 
vide adequate coverage, and to minimize time 
required for arriving at a particular distress 
position. Planes and boats must be manned 
and equipped to carry out rescue missions ex- 
peditiously, and to function as a team, utilizing 
each other’s capabilities with regard to speed, 
range, methods of search, and rescue. It is 
essential that planes and boats be organized 
and dispatched collectively as rescue squadrons 
or task units to facilitate standardization of 
procedures, equipment, and training. 
Air-land rescue organization.—In land areas 
where flying is concentrated, the same principle 
of centralized control of rescue forces is in- 
dicated. On the coasts it is advantageous to 
exercise direction over both land and sea rescue 
facilities from the same point, since aircraft, 
amphibious vehicles, and other equipment fre- 
quently can be used interchangeably. 
Air-land rescue facilities are composed of 
highly trained mobile units, located at strategic 
spots, and capable of being moved by air to the 
locality where such facilities are needed within 
a given area. 
RESCUE PROCEDURES 
Principles.—Basic principles of successful 
rescue operations require planned methods for: 
anticipating distress incidents when operations 
permit; promptly reporting and relaying dis- 
tress information; promptly dispatching ade- 
quate assistance; and following through rescue 
operations to completion. 
Delivery of distress information requires an 
adequate communication system. The dispatch- 
ing of assistance is a matter of doctrine; usu- 
ally at least one rescue plane and one rescue 
vessel should proceed immediately, notwith- 
standing any othev action which has been or 
will be taken. Speed is paramount throughout. 
Rescue aircraft and vessels operate as a 
group to accomplish a common mission, and 
the essence of successful operation is close 
teamwork. The primary purpose of the planes 
is to locate survivors, drop equipment to sustain 
them, and direct the boat to the scene. Ordin- 
arily the boat is to pick up survivors, provide 
first aid, and deliver them ashore. 
Offshore landings by rescue aircraft are not 
made when rescue can be accomplished by 
other means without jeopardizing the lives of 
the survivors. Occasionally rescue pilots, in 
their efforts to help fellow aviators, have landed 
unnecessarily, with disastrous results. How- 
ever, there are unusual circumstances wherein 
the pilot of the rescue plane will determine 
that an open sea landing is necessary, as when 
a survivor is injured or suffering from ex- 
posure, when darkness is approaching, or when 
the nearest surface vessel is too far away. In 
such cases, the rescue pilot bases his decision 
on his knowledge of the situation, the capabili- 
ties of his aircraft, and the calculated risk to 
his own crew. 
Rescue pilots are given broad discretion and 
are instructed that in cases where communica- 
tions fail or emergency action is indicated, they 
are expected to act immediately on their own 
best judgment. In any case the final decision 
as to the feasibility of making an open sea 
landing can be made only by the rescue pilot. 
210 Chapter 12. — OPERATIONAL PROBLEMS IN AVIATION MEDICINE 
Cycles of rescue operations.—A probable 
cycle of rescue operations will be as follows: 
A plane in trouble, or an accompanying plane, 
indicates potential or actual distress by radio 
and/or IFF signals (radio identification sig- 
nal). Receiving stations then relay the infor- 
mation to the rescue operations center. The 
rescue operations center utilizes all available 
communications and direction finder facilities. 
It maintains plot of action, dispatches primary 
(and secondary when necessary) rescue craft, 
follows through all incoming and outgoing re- 
ports, monitors radio communications, when 
possible, arranges fighter support when re- 
quired, keeps informed on weather, and desig- 
nates “on scene” commander, who may be: 
senior officer present at scene, or commanding 
officer of the first air or surface craft to arrive 
on scene. 
Rescue craft proceed, conduct search, and 
locate survivors. Survivors are then picked up, 
given medical attention, and landed ashore. 
Aircraft distress procedure.—Rescue can be 
accomplished most expeditiously by the intelli- 
gent cooperation of personnel involved in a 
distress incident. It is important that the first 
step in effecting a rescue be taken by the 
pilot who experiences an emergency or who 
observes a distress incident. 
The pilot in trouble must: 
Immediately switch on his emergency IFF 
signal. (All aviation personnel must be famil- 
iar with this equipment in order to insure its 
positive use when needed and to prevent its 
misuse when not needed.) 
Immediately transmit distress messages by 
radio to his own base if possible, or to any 
shore station, vessel or aircraft, giving identity 
and position, (An accurate position is impor- 
tant, but an approximate position reported 
promptly is preferable to delayed exact posi- 
tion.) Plain language should be used, if local 
regulations permit. Voice should be used in 
preference to CW (Code) whenever practicable. 
Indicate that an emergency exists by any 
available visual means—flares, lights, hand sig- 
nals, etc. 
If time permits, transmit the following ad- 
ditional information: Altitude, course and 
speed. Nature of distress. Intentions (such 
as ditching, bailing out, etc.) 
Rescue Operations Procedure.—The next step 
is taken by the base (or ship) which receives 
a message concerning distress. This base im- 
mediately should dispatch such assistance as 
may be available locally (if the distance is not 
too great) and notify rescue operations center. 
A form for such reports might be as follows: 
1. Exact location: By a known geographic 
point or bearing and distance therefrom. 
By latitude and longitude. 
By the operating area grid position. 
2. Time of crash. 
3. Source of information. 
Name of informant. 
Address (or service and command). 
Telephone number. 
4. Type of plane and designating number. 
5. All information known as to personnel. 
Number involved. 
Whether ditched or bailed out. 
Whether known to be afloat, whether they are 
wearing life vests, whether in a life raft. 
6. What search or rescue has been instigated 
locally. 
By what agency. 
What equipment available. 
Obviously, all the above information is sel- 
dom available immediately but 1, 2 and 3 should 
in every case be included in the first report in 
order that intelligent action may be started. 
Additional information should be the subject 
of amplifying reports, as available. 
Rescue operations center dispatches rescue 
aircraft and vessels as circumstances require, 
and delivers to them sufficient information to 
describe the situation and indicate the neces- 
sary action. Instructions to proceed, whether 
given directly or by radio, should inform rescue 
craft as to: 
Type of aircraft and number of personnel. 
Whether personnel ditched or parachuted, 
whether in sea with life vests or in life rafts. 
Position (preferably in bearing and distance 
from land, or latitude and longitude). 
Craft present at scene or proceeding. 
Any other available basic information. 
Subsequent information is reported to rescue 
craft by radio immediately upon receipt. 
Rescue Plane Procedure.—When a search 
aircraft is dispatched on an emergency rescue 
211 AVIATION MEDICINE PRACTICE 
Figure 12-1.—Rescue operation by PBY. 
mission, it immediately establishes communica- 
tion with rescue operations center. 
During the search all possible observation 
points for lookouts should be filled by aircrew 
members. The lookout or searcher who makes 
a sighting' reports immediately to the pilot on 
the interphone, giving the relative bearing. The 
pilot immediately drops a float light or, if avail- 
able, a radio marker buoy. Float lights can 
best be dropped when carried in flare chutes. 
The pilot should glance at his compass when 
he makes the drop so that he may combine 
plane heading and relative bearing to get the 
compass bearing of the survivor from the 
marker. 
The pilot should not delay dropping the first 
marker until directly over the survivors, but 
should use the bearing and distance of the sur- 
vivors from the marker for relocating them. 
Without this step—particularly if the survivors 
are in a heavy sea—the danger of losing them 
is very great. 
When survivors are seen by pilot, he should: 
1. Fly directly toward them, keeping them 
always in sight, and when passing over the 
survivors, he should drop a drift signal and 
dye sea marker directly alongside. Dye marker 
never should be dropped any great distance 
away from survivors, since it lasts a consider- 
able time and may result in misleading other 
searching aircraft. Float lights are used when- 
ever desired since they last only a few minutes 
and are recognized as having come from air- 
craft and not from survivors. 
2. Switch on emergency IFF signal. 
3. Report situation to controlling ship or 
station as soon as possible, and transmit hom- 
ing signals for rescue craft. Under ordinary 
circumstances this report will include: 
The position. 
Number and condition of survivors. 
State of sea. 
Location of nearest surface vessel. 
Plan of action. 
4. Remain on scene until relieved, recalled, 
rescue is accomplished, or fuel is running low. 
5. Facilitate rescue: To facilitate rescue, 
the rescue plane pilot may: 
Drop flotation, sustenance and communica- 
tion equipment, Life raft (multiple unit as- 
212 Chapter 12. — OPERATIONAL PROBLEMS IN AVIATION MEDICINE 
sembly or airborne lifeboat if available), if 
survivors are without flotation aids. Ration kits 
and/or shipwreck kits, if it is apparent that 
rescue will be delayed. 
Communication equipment and night marker 
signals, if near nightfall, or if forced to leave 
scene without being relieved. 
6. Direct a rescue aircraft, boat, or other 
surface vessel to the scene. 
7. Land and effect a rescue. 
8. Request further assistance from rescue 
operations center. None of these actions pre- 
cludes the use of any other. 
There are several ways in which surface 
vessels can be led to the scene by a rescue air- 
craft : 
1. The plane can drop float lights or fire 
pyrotechnics. 
2. The plane can transmit homing signals 
for the ship. 
3. The plane can zoom the survivor’s posi- 
tion (preferably across the line of sight from 
the ship to the survivor. 
4. The vessel can follow IFF signal and 
radar reflection. 
5. If the vessel is not equipped with DF 
(direction finder), the homing procedure can 
be reversed: the plane can take a bearing on a 
signal from the vessel and give a course to be 
steered. 
6. The plane itself can divert and convoy 
a vessel to the scene by the standard method 
provided that at least one aircraft is left with 
the survivor. 
When leaving scene, for any reason, pilot 
must switch off the emergency IFF signal. 
Unnecessary aircraft should leave the scene, 
as directed by the “on-scene commander.” Cas- 
ual aircraft should keep clear once survivors 
are located. 
Rescue Boat Procedure.—The officer-in- 
charge of a rescue boat should consider his 
vessel as a component of the rescue team and 
be prepared to perform his mission as follows: 
1. Proceed with all practicable speed to-the 
distress scene. 
2. Establish and maintain communication 
with rescue control and rescue aircraft. 
3. Monitor proper frequencies on DF equip- 
ment for homing on orbiting aircraft, “Gibson 
Girl” or radio marker buoy signals. 
Figure 12-2.—Rescue operations by AVR, 
4. Conduct search operations in cooperation 
with rescue aircraft. 
5. Locate and pick up survivors. 
6. Render first aid to survivors as neces- 
sary. 
7. Transfer seriously injured survivors from 
boat to plane and other surface vessel. 
8. Buoy location of wreckage when practi- 
cable and when it does not interfere with as- 
sistance to survivors. 
The plane or vessel effecting a rescue should 
report the following information to rescue op- 
erations center as promptly as possible: 
1. Total number personnel rescued. 
2. Total number personnel injured. (If seri- 
ously ill or injured give name, condition, treat- 
ment rendered and effect thereof.) 
213 AVIATION MEDICINE PRACTICE 
Figure 12-3.—Rescue craft, AYR and lighter-than-air craft. 
3. Total number personnel dead or missing. 
(Give names if available.) 
4. Destination to which proceeding and esti- 
mated time of arrival. 
Rescue craft.—No airplane available today 
has been designed especially for rescue pur- 
poses, and no existing airplane possesses all 
the necessary requirements. However, several 
types of military aircraft are being used for 
rescue operations, and these are satisfactory 
if their limitations are borne in mind by operat- 
ing personnel. Important characteristics in a 
rescue seaplane are: 
1. Good visibility, for aerial search. Ade- 
quate communication and search equipment. 
2. Suitable bomb bays and hatches for car- 
rying and dropping equipment. 
3. Rugged design, for rough water work. 
4. Low wing loading and favorable power- 
weight ratio. 
5. Good maneuvering and taxiing qualities 
on the water. 
6. Suitable hatches and hoists for passing 
survivors. 
7. Adequate facilities for berthing and treat- 
ment of survivors. 
8. Moderate cruising speed. 
9. Reasonably long range. 
The Catalina airplane is common to all U. S. 
services in rescue operations. Where rough- 
water work is required, the seaplane type is 
preferable to the amphibian because of its 
lighter weight. 
214 Chapter 12. — OPERATIONAL PROBLEMS IN AVIATION MEDICINE 
The Mariner has come into extensive use as 
a rescue aircraft. 
The Coronado has been used for long-range 
search and for carrying rescue equipment. 
Where operating conditions permit, rescue 
seaplanes can be stripped of all equipment not 
directly essential to rescue, to lighten the plane 
and thereby improve its possibilities in rough- 
water work. Removal of such items as heaters, 
oxygen equipment, torpedo racks, machine 
guns, self-sealing fuel tanks, etc., will reduce 
considerably the gross weight. 
Rescue Landplanes.—Where water operation 
is not required, the landplane is of major value 
in air sea rescue as a search plane and carrier 
of droppable rescue equipment. 
Land-based fighter planes have been used and 
carrier-based fighters are being used more and 
more extensively for rescue operations of 
limited range. Fighters are extremely valuable 
for getting to a survivor’s position quickly and 
directing surface craft to the position. A group 
of such planes can sweep a large search area 
in minimum time. 
Rescue boats.—Rescue Boats may be separ- 
ated into four categories: 
Self-sustaining offshore type. 
Offshore, shore based type. 
Inshore type. 
Shallow-water type (swamp gliders, etc.). 
Features of a rescue boat which must be 
considered in selecting a boat for use in a par- 
ticular area are: 
1. Maximum practicable delivery range un- 
der own power. 
2. Lifts and weights involved in deck load- 
ing for delivery. 
3. Fuel, oil and water capacities and rates 
of consumption. 
4. Ease of maintenance. 
5. Size of crews required. 
6. Seaworthiness. 
7. Communication equipment. 
8. Casualty handling facilities. 
9. Endurance range. 
10. Speeds, maximum and cruising. 
Lighter-than-air craft.—The lighter-than-air 
craft are used when available as rescue craft. 
The non-rigid airship has certain peculiar ad- 
vantages including: 
Ability to cover any area with a balance 
between area searched and thoroughness of 
search. In covering a well-defined area, an LTA 
(Lighter-than-air) can cruise slowly at low 
altitude and make use of its steady search 
platform and excellent visibility. It can hover 
in moderate winds, when it is desired to ob- 
serve a particular position, or remain over a 
survivor. Ability to assist in coordinating res- 
cue action on the scene. After a survivor has 
been located the LTA frequently can establish 
and maintain visual and verbal contact with 
him to determine his condition and situation. 
Ability to drop or lower survival and rescue 
equipment with more accuracy than heavier- 
than-air craft (except helicopters). Ability 
to conduct night search at slow speed with the 
use of search lights. Ability to rescue survivors 
by means of lowering a harness similar to the 
chestpack parachute harness. (However, this 
maneuver is difficult even for experienced 
lighter-than-air pilots and requires a moderate 
wind.) 
Helicopters.—The helicopter is in use in cer- 
tain areas for limited operations. Difficulties 
experienced in present operational models are 
being overcome as rapidly as possible. Improved 
models are in design and at such time as they 
are placed in large scale production they will 
probably figure prominently in rescue opera- 
tions. 
SURVIVAL 
Life raft drinking water.—Under conditions 
of minimum water loss, an individual consum- 
ing 75 to 125 grams a day of a food constituted 
of carbohydrate and up to 20 percent fat will 
not become severely dehydrated for at least 8 
days if supplied with 500 cc. of water a day. 
Given the same amount of food, a water supply 
of 800 cc. a day will provide for water needs 
indefinitely under these conditions. In the pres- 
ence of complete starvation, the water require- 
ments are slightly augmented. 
It seems likely that loss may be maintained 
at a minimum in all tropical ocean areas by 
observing the following procedures: 
1. Preventing vomiting. 
2. Minimizing evaporative water loss by: 
a. Refraining from unnecessary exertion. 
215 AVIATION MEDICINE PRACTICE 
b. Exposing the body, adequately pro- 
tected against sunburn, to the breeze as much 
as possible. 
c. Shading the body from the sun, with- 
out simultaneously cutting off the breeze. 
d. Keeping the clothing wet with sea 
water in the daytime. 
Procedures 2 b. through 2 d. should be dis- 
continued when sensations of chilliness inter- 
vene, since cold and consequent shivering ex- 
pedite exhaustion and cause water to be lost 
from the body unnecessarily. 
There should be made available on life rafts, 
from all sources, a minimum of 500 to 800 cc. 
of water per man per day of the estimated 
maximum number of days before rescue. Rain 
catchment equipment should also be provided. 
As regards the proper procedure for ration- 
ing water, uninjured survivors should drink 
no water the first day. Thereafter, if the supply 
is limited, water should be consumed at the rate 
of 500 cc. per man per day until the supply is 
exhausted. When finally no water remains, 
individuals can survive several additional days, 
providing that from the very start the survivors 
maintain unnecessary water loss from the body 
at a minimum by using the procedures recom- 
mended in an earlier paragraph. 
Producing drinking water at sea.—Three 
particular methods of producing drinking water 
at sea have been developed. They are: 
1. Removal of salts from sea water by addi- 
tion of chemicals. 
2. Distillation of fresh water from salt 
water by small fuel-burning stills. 
3. Distillation of fresh water by “Solar 
Stills”, using sun alone. 
Chemical desalination is not based upon a 
new principle. Patents relating to this method 
were taken out as early as 15 years ago. The 
Navy desalination kit occupies the same space 
as one 12-ounce can of water, weights 2 pounds, 
and contains 6 briquets which will render 6 
pints of water. 
Fuel stills for distilling fresh water from 
sea water are not new in principle either, many 
of them have and are being used. But develop- 
ment of small portable stills designed for use 
in lifeboats and rafts is recent. The Navy ob- 
tained some 8 pounds safety stills for use in 
rafts on large patrol aircraft. 
The solar still is the most recent of the three 
water producing methods. This still, which is 
standard equipment for single or multi-placed 
life rafts, can produce more than two pints of 
fresh water a day. Although the still needs 
direct sunlight to operate best, it will work to 
some extent if the overcast is not too heavy. It 
will not work at night or on very dark days. 
When the still is inflated it floats in the water 
alongside the raft. Sea water is poured through 
the funnel in the top of the still. The removal 
of salt from the water is accomplished by distil- 
lation. The sun’s rays heat the sea water that 
drips on the black evaporator cloth stretched 
in the center of each still causing evaporation. 
Vapor condenses on the sides of the plastic 
cover in little beads which run down to the 
fresh water trap below the ballast tube. The 
salts do not evaporate, but remain in the black 
cloth. This salt is washed out through the drain 
in the bottom of each still. They are self clean- 
ing and never require washing. 
Life raft rations.—Because of limitations of 
space, no more than a fraction of the approxi- 
mately 2,000 calories per day needed by a cast- 
away can usually be provided in an emergency 
ration. A daily intake of 75 to 125 grams of a 
food constituted of carbohydrate and up to 20 
percent fat effectively spares body water and 
tissue and hence should be included in raft kits. 
Up to 125 grams per day of such a ration is 
more than its weight in water. 
On the basis of the information now avail- 
able, and for several practical reasons, it would 
seem inadvisable to include more than 25 per- 
cent fat in a ration for use on lifeboats and 
rafts. Except as a matter of palatability, pro- 
tein should not be contained in an emergency 
ration for these craft. Addition of protein in 
order to increase palatability is at the expense 
of the more physiologically economical carbohy- 
drate. The concentration of any flavor should 
be minimal and a variety of flavors should be 
provided, if possible. The vitamins available 
in the rafts today merely stimulate the morale 
so far as castaways at sea are concerned. 
The emergency ration now contained in Navy 
life rafts consists primarily of carbohydrates. 
They replaced the former emergency ration 
which consisted of chocolate, malted milk, and 
“pemmican”. The new ration was designed to 
216 Chapter 12. — OPERATIONAL PROBLEMS IN AVIATION MEDICINE 
Figure 12-4.—First - evacuation flight by Navy. 
AIR TRANSPORTATION OF PATIENTS 
Not until after World War I was aerial trans- 
portation accepted as a method of transporting 
patients. The first known Navy transportation 
of a patient by air was-at Key West in 1919 
when one patient was transported in an H-l 
boat. Prior to World War II patients were 
transported by air only on rare occasions. It 
was not until after the beginning of World War 
II that air evacuation became an organized pro- 
gram and this was the result of necessity and 
not of choice. An example of situations present- 
ing such necessities was the air evacuation from 
Guadalcanal in 1942. These experiences in the 
movement of casualties with practically all de- 
grees of wounds and illnesses proved that air 
evacuation was both safe and reliable. 
In 1942, R4D planes were being used, aboard 
which approximately 12 to 16 patients were 
be easily edible and physiologically compatible 
when the water supply is limited, to provide a 
variety of items, and to be compact and easily 
stowable in parachute back pack kits. 
This emergency ration is packed in a 3 by 2 
by 1 inch key opening tin container and con- 
tains the following items: 
Number Item 
5 ........ Sucrose-citric acid tablets. 
10 Sucrose-lipid-citric acid tablets. 
8 Sucrose-malted milk tablets. 
2 Multivitamin tablets. 
2 Sugar coated gum tablets. 
1 Waterproof cellophane bag. 
2 Clips for closing bag. 
At present three of these cans are supplied 
per man in parachute seat type and multiplace 
rafts. A survivor consuming one half a can a 
day will derive about 190 calories daily. 
217 AVIATION MEDICINE PRACTICE 
Figure 12-5.—Evacuation from Okinawa. 
218 Chapter 12. — OPERATIONAL PROBLEMS IN AVIATION MEDICINE 
transported. By 1945 the planes in use were 
USD’s which transported 30 to 34 patients. 
Then in 1947 the JRM (Mars) planes began 
transporting 100 patients (84 litter and 16 am- 
bulatory) per trip between Honolulu and Ala- 
meda, California. Now, of course, we have 
planes which can transport much larger groups 
of patients. 
Advantages of transportation of patients by 
air.—Transportation of patients by air has 
many advantages over surface transportation. 
Some of these are: (1) Greater morale building 
factor for men in combat to know that if they 
are injured or become ill that they will soon 
be moved by air out of combat area to rear area 
hospitals. (2) Conserves medical personnel and 
equipment in that movement by air is accom- 
plished in a few hours, thus usually requiring 
only a flight nurse and flight corpsman. Slower 
means of transportation such as by ship re- 
quires much longer periods of time, necessitat- 
ing the presence of doctors, additional nurses 
etc., and much more medical equipment. (3) 
Patients better tolerate short trips by air and 
so arrive in better physical and mental condi- 
tion than they would if transported by slower 
means, such as by ship or train. (4) It is more 
economical to transport patients by air than by 
ship. Studies show that three R5D planes can 
move the same number of patients between two 
points that can be transported by a hospital 
ship. Three planes can operate much more 
economically than a hospital ship. (5) Some 
cases tolerate air travel whereas it is highly 
questionable whether they could tolerate a long 
sea voyage. Examples are cases of leukemia 
and metastatic carcinoma with marked anemia. 
For humanitarian reasons the policy of the 
Navy in such cases is to return them to the 
Naval hospital nearest their home before they 
expire. This is accomplished by giving the 
patient several blood transfusions and then 
transporting him by air to the desired hospital. 
Such a procedure would be most difficult, if not 
impossible, by surface transportation in cases 
of long distances such as from China or the 
Phillipines to the United States. Numerous 
cases such as these have been successfully 
transported by air. 
At the beginning of the program in 1942 
medical personnel were not specially trained 
for air evacuation work but as the program 
progressed a special school was established to 
train flight nurses and flight corpsmen. This 
school gave them special training in the care 
of patients aboard aircraft. 
Very soon after the beginning of the air 
evacuation program it was found that the pa- 
tients could be better cared for if they were 
observed and studied in the hospitals by the 
flight medical teams before they were taken 
aboard for transportation. This procedure is 
referred to as “screening” the patient. In time 
it became the policy for each plane load of 
patients to be screened by the flight nurse and 
flight corpsmen who were to accompany them 
and also to be seen by the flight surgeon at- 
tached to the unit. The flight surgeon, after 
visiting the patients would advise any special 
care which was indicated for the patients on 
the flight. 
Practically all types of cases have been suc- 
cessfully transported by air. A general rule 
to follow in determining whether or not a 
patient should be transported by air is to deter- 
mine whether or not he will be adversely af- 
fected by altitude. The type patients generally 
not acceptable for air transportation are as fol- 
lows : 
1. Patients in such poor physical condition 
that the successful completion of their evacua- 
tion is doubtful, unless potential lifesaving 
measures are available at the destination hospi- 
tal which are not available at the point of 
origin. 
2. Patients with fatal prognosis in moribund 
or semi-moribund state. 
3. Patients whose illnesses present a health 
menace. These cases include quarantinable 
diseases (small pox, typhus, plague, cholera, 
yellow fever, leprosy) and other contagious or 
communicable diseases where adequate caution 
to prevent spread is impracticable or not fea- 
sible, 
4. Patients in shock. 
5. Patients with coronary occlusion or an- 
gina pectoris, if an attack has occurred within 
thirty days. 
6. Patients with severe anemia. Severe an- 
emia is defined as corresponding to a red blood 
count of 2.5 million or less and/or a hemoglobin 
of 50% or less. 
219 AVIATION MEDICINE PRACTICE 
Figure 12-6.—One hundred patients transported on Mars. 
During a hospital flight a complete record is 
kept of the patient. The flight nurse does this 
by use of a special form on which is recorded 
any changes in the patient’s condition, medica- 
tions given, etc. This record, with the patient’s 
other records, accompany him to the hospital. 
Experience has shown that mental patients 
tolerate air travel better than any other type 
of transportation. This is due to the fact that 
they can be sedated in the hospital and kept 
sedated during the flight. Sedation is not prac- 
tical for other means of transportation because 
of the lengthy periods involved. 
Cases of advanced pulmonary tuberculosis 
present a problem to air transportation in view 
of the fact that it is highly questionable how 
well they will tolerate altitudes at which flights 
are usually made. This problem has been solved 
by loading a plane with such cases and then 
making a special flight at low altitude. Such a 
procedure has been quite successful. 
Other special type cases which have been 
successfully handled by air transportation are 
cases of poliomyelitis with respiratory paralysis 
which require a respirator. This is accom- 
plished by use of a portable respirator which 
operates either directly from the ship’s current 
of 24 volts or from a current of 110 volts. In 
case of emergency the respirator can be oper- 
ated manually. These portable respirators are 
readily available upon request to the Military 
Air Transport Service, 
The medical personnel in the air evacuation 
program greatly assist in the overseas trans- 
220 Chapter 12. — OPERATIONAL PROBLEMS IN AVIATION MEDICINE 
portation of dependents because medical as- 
sistance is often necessary on such flights. This 
is due to the fact that there are often a number 
of pregnant women and small children aboard. 
A Bureau of Medicine and Surgery Circular 
Letter (No. 47-143) describes the procedure 
for requesting transportation of patients, trans- 
portation requirements, instructions, etc. 
AVIATION SAFETY 
The interrelationship between human factors 
and the type of aircraft is especially pertinent 
in an analysis of accidents because neither the 
operating characteristics of the plane nor the 
performance of the pilot can be considered 
as completely separate variables. Only in iso- 
lated cases is it possible to apportion the causes 
of an accident to specific faults rather than to 
an accumulation of contributing factors. Many 
accidents that have been attributed to pilot 
error may have resulted from excessive de- 
mands on the air crews. While training and 
selection procedures may be improved, it is 
unlikely that human limitations in operating 
aircraft can be appreciably altered. The aero- 
nautical engineer may, however, be able to 
simplify the duties of the pilot and thus reduce 
the likelihood of error. 
Methods of Accident Analysis and Preven- 
tion.—There are three main classifications that 
might be conveniently used to describe the 
methods of accident analysis. The first includes 
post accident studies which attempt to allocate 
the blame for what happened and to suggest 
subsequent corrective measures. This method 
has been most widely used and lends itself read- 
ily to statistical treatment. The second is the 
study of near accidents and the third an advance 
analysis of all possible causes. The two latter 
methods place greater emphasis on preventive 
thinking and on the correction of faults as 
they are brought to light before an accident. 
They should be given primary consideration. 
Post-accident analysis.—This method in- 
volves the tabulation of the various contribut- 
ing factors believed to have caused an accident, 
although they rarely occur as single events. 
The tendency of certain basic causes of acci- 
dents to repeat themselves in a general way 
makes the tabulation of frequency distributions 
of some significance. Many breakdowns re- 
lating to causation have been proposed, but the 
following one is representative of the majority 
now in use and indicates briefly the usual 
distribution of responsibility: 
1. Human factors.—By far the greater per- 
centage of accidents is attributed to such human 
limitations as errors of judgment, inadequate 
training, poor technique, loss of emotional con- 
trol, disobedience of orders, and exhibitionism. 
Some studies of accidents in air operation at- 
tributes 75 to 85 percent of the causes to human 
failure in one form or another. There are many 
shortcomings to this classification, not only 
because it presupposes a perfect pilot, but be- 
cause there is a tendency to place the responsi- 
bility on errors of judgment when no other 
obvious cause is present. This category also 
includes errors made by the flight crew, main- 
tenance personnel or supervisory personnel. 
2. Weather and meteorological factors.— 
Poor visibility, extreme turbulence, icing, snow, 
hail, lightning, precipitation, static, and heavy 
rains are occasionally given as the direct cause 
of an accident. Some of these hazards may act 
in combination with poor weather-proofing of 
the windshield or ineffective deicing systems to 
increase the danger to a flight. Weather may 
occasionally be a factor in ground accidents; 
e.g., gale winds may upset an aircraft, 
3. Material failures.—The most important 
cause of accidents in this classification is mal- 
functioning of the power plants, propellers, 
landing gear, or such accessories as hydraulic, 
electrical, and fuel systems. In addition, there 
may be structural failure of the airframe 
itself but this is rare unless the aircraft is 
placed under extreme stress. 
4. Poor flight characteristics.—The aircraft 
may be well built structurally but have certain 
deficiencies in operation which involve both 
the performance of the plane and the ability 
of the pilot to compensate for them. It is well 
known that some models may have dangerous 
flight characteristics, such as the dropping of 
a wing on landing, excessive loss of altitude on 
turns, or inadequate warning of the onset of 
a stall. 
5. Airport and ground facilities.—Many air- 
ports have inherent defects that may cause ac- 
cidents. Runways may be inadequately lighted 
221 AVIATION MEDICINE PRACTICE 
or marked or too short for the type equipment 
being flown. Some airports even have embank- 
ments, levees, ditches, or other obstacles at the 
end of runways; e.g., they may be so laid out 
as to prevent a desirable field of view or to 
expose aircraft to perennial cross winds. 
6. Miscellaneous.—This category includes 
the freakish types of accidents such as those 
caused by bird strikes or by temporary blinding 
with bright flashes of light from unexpected 
sources. 
Considerable progress has also been made 
by the services in systematizing the study of 
accidents through standardization of accident- 
investigation procedures. A survey of the scene 
of the accident can be made and the relative 
positions of various parts of the wreckage 
studied. Very often the flight path of the air- 
plane can be deducted by an examination of 
ground scars and of trees or brush broken by 
the propellers, landing gear, or wing tips. In 
this way the angle and attitude in which the 
plane struck the ground can be determined. 
For example, if the wreckage is confined to a 
small circular area, it may have dived directly 
into the ground. By similar projection analysis, 
it can sometimes be established whether the 
plane spun in, hit the ground in low level flight 
or was completely out of control while on in- 
struments. There are many uncertainties and 
inadequacies in such methods, and great care 
must be exercised in attempting to reconstruct 
the sequence of events, particularly if there 
has been a fire and it is necessary to determine 
whether it started before or after the impact. 
Photographs, sketches, maps, and evidence from 
witnesses are often helpful for the permanent 
records and later study. Closer liaison between 
engineers and medical officers has contributed 
greatly to post-accident analysis, especially in 
correcting defects in the design of the seats, 
cockpits, and instrument panels. The nature 
of personnel injuries in relation to a study of 
the wreckage will often reveal whether the 
seats and safety harness were adequately 
stressed or whether protruding objects in the 
cockpit or on the instrument panel were con- 
tributing factors. 
When a large number of accidents occur, 
as during the World War II, it is possible to 
put all available information on cards for use 
in automatic tabulating machines. Frequency 
distributions obtained by this procedure may 
be of significance in showing which variables 
have greater implications for safety. If a large 
number of crashes occur at night during ap- 
proaches and landings, or because of failures in 
any one part of the plane, it may be possible 
to establish a single causative factor. Through 
such studies it has been possible to make no- 
table progress in the safety program by chang- 
ing the regulations to diminish the likelihood 
of the reoccurrence of any given type of acci- 
dent. The fundamental weakness of this ap- 
proach, however, lies in the possibility that the 
data may have been inadequately selected or 
improperly tabulated on the punch cards by 
someone who is not familiar with aircraft 
operation and that questionable inferences have 
been drawn from them. In many instances 
when there are no survivors and the plane is 
completely destroyed the accident must be re- 
constructed from circumstantial evidence alone, 
introducing additional sources of error. 
Analysis of near accidents.—A study of near 
accidents is of more importance to the safety 
of operations than information about those that 
have already taken place because it is possible 
for the flight crews and engineers to suggest 
corrections in design or in operating procedure 
before a real mishap occurs. The greatest draw- 
back in this method is the difficulty in enlisting 
the complete cooperation of the flight crews, 
for they might be reluctant to give evidence 
implying negligence on their part. When com- 
plete confidence is obtained between flight 
groups and management and when there is less 
readiness to assign an accident to human fail- 
ure alone, this approach may be very productive 
of constructive criticism of both the operation 
and design of the aircraft and the performance 
of the air crews. Pilots have grounded them- 
selves because of excessive fatigue, poor health 
or inadequate training on a particular type of 
aircraft; this cooperation was possible because 
complete confidence existed between the flight 
group, the operations officer, and the medical 
officer. Numerous illustrations can be given in 
which pilots have reported near accidents due 
to poor operating procedures, faulty design 
features in aircraft or defective airports. When 
corrective measures are not carried out, sooner 
222 Chapter 12. — OPERATIONAL PROBLEMS IN AVIATION MEDICINE 
or later severe accidents occur. Near-accident 
analysis, however, places less emphasis on pre- 
ventive measures than does the approach out- 
lined below, which stresses advance analysis 
of all aircraft operations and aircraft design. 
Advance analysis of accidents.—An effort 
should be made to prevent the occurrence of 
accidents by an advance analysis of possible 
contingencies that might arise while the plane 
is in flight. This method involves a study of 
(1) mistakes that the air crews may make and 
(2) every possible fault in the design of the 
aircraft itself. The point of view represented 
by the word defect or fault may be more fitting 
to use in this approach than accident. The im- 
plication is that it would be more fruitful to 
determine the predisposing factors leading up 
to a crash or near crash by studying the design 
and flight characteristics of the plane, as well 
as the limitations of the pilot and what may 
reasonably be expected of him. For example, 
it might be questioned whether the probable 
cause of an accident lies in the pilots failure 
to compensate for a plane’s tendency to drop a 
wing in a turn or in a defect in the design of a 
plane. It would be appropriate to consider 
whether such a basic fault in flight character- 
istics could not have been corrected at some 
stage in the design and construction of the air- 
craft. If such a defect is present, it is only a 
question of time before some pilot “fails” and 
crashes the plane. 
Accidents occurring in naval aircraft are 
reported and studied in accordance with Avia- 
tion Circular Letter No. 97-48 through the use 
of a “Medical Officers Report of Aircraft Acci- 
dent”. These reports are now required on each 
accident resulting in injuries (treated or not), 
deaths, and all bailouts and ejections (includ- 
ing those resulting in no injuries). The flight 
surgeon or unit medical officer should submit 
this form direct to Chief of Naval Operations, 
Attention: Flight Safety, in accordance with 
instructions thereon. An example of the “Medi- 
cal Officers Report of Aircraft Accident” is 
shown in Figure 12-7. 
Protection of crews and passengers against 
high deceleration during impact.—When an air- 
craft strikes the ground at a sharp angle at 
high speed in crash landing, its structure col- 
lapses suddenly and the passengers are un- 
likely to survive. In extreme impacts there is 
a complete disintegration of plane and bodies. 
In many crashes, however, the angle and the 
force of impact are not extreme, and a sub- 
stantial portion of the cockpit or cabin remains 
intact. This type of crash may be termed 
“marginal” and injury or fatality may not 
occur. In marginal crashes, injuries largely 
result because the occupants are thrown against 
those portions of the plane that remain intact. 
The decelerations that the human body can 
tolerate vary greatly with the position of the 
body at the time of impact and with the dura- 
tion and distribution of the impact force. A 
study that is directly applicable to the influence 
of the positioning of the body has been reported 
by Henchke. Human subjects assumed various 
positions on the platform of a large swing 
that could be stopped very suddenly. The maxi- 
mum force in g which the human body can 
withstand in any given position was determined 
by the onset of headaches or other symptoms 
of cerebral concussion. The duration of the 
decelerative force for all positions was 0.01 sec. 
One position is of particular interest in aviation 
since it corresponds most closely to that of a 
person in a seated position and wearing a 
safety belt. The values of g were somewhat 
high since they probably referred to the decel- 
erative forces on the swing rather than on the 
body and also because the duration was limited. 
It can be concluded from this study that safety 
belts, seats, and other items with which the 
subject is in contact at the time of impact 
should be stressed to withstand forces of at 
least 34g and preferably 40g to insure an ade- 
quate safety factor. 
The importance of a proper distribution of 
pressure forces over the body during sudden 
impact has been demonstrated by DeHaven 
in a study of survival after falls from heights 
of 100 to 150 feet. He estimated that in some 
of the accidents that he has studied approxi- 
mately 200g has been imposed on the body with- 
out serious results. This investigation was then 
extended in to the field of light aircraft acci- 
dents and an analysis has been made of the 
injuries incurred. The most important impli- 
cations of these studies are that (1) the force 
of many accidents now fatal is well within 
physiological limits of survival, (2) needless 
223 AVIATION MEDICINE PRACTICE 
MEDICAL OFFICERS REPORT OF AIRCRAFT ACCIDENT OP-REP-59-11 
■AVAEN->>{« (REV. D-Ni) 
GENERAL INSTRUCTIONS 
AVIATION CIRCULAR LETTERS 
1. This report shall he filed »* the eveut of any and all aircraft 
accidents rssulting in tn>wr««* to plane occupants, treated or 
not, regardless of extent or tyPee, and ALL bailouts, injured or 
not. 
3. Completion of the form shall be the responsibility of the flight 
surgeon serving as an sx officio member of the Aircraft Accident 
Board. He shall be assisted by the medical officer first report- 
ing to the scene of the accident, or tn tkt event no suck officer 
reports to the scene, by the officer supervising treatment of the 
injured. 
j. This form shall he Prepared in duplicate, the copy be tug turned 
over to the Aircraft Accident Board and the original nailed di- 
rect to Chief of Baval Operations tPLIGBT SAFETY). Hvy Depart- 
ment, Washington 35, D.C., within 96 hours following first <xnr- 
tnctieM of the injured. Where more than one aircraft is tmvolvsd, 
separate forms nit be c pmpleted for each craft where in occupants 
were injured. (Additional copies may be prepared for «*< of 
tquadro n flight surgeons • nd other interested tndividua Is. f 
4. Include photographs illustrating impact (s), damage (0 cockpit, 
structures causing injury, etc. 
5. Addenda are encouraged. 
PART I. ACCIDENT IDENTIFICATION 
I. REPORT FROM (Ship or stwlio* address) DATE 
T. ACCIDENT OCCURRED (Oeographie location} TIME DATE 
J. PLANE COVERED 8Y THIS REPORT (Bureau to.} (Type) (Init assigned to) 
I. OTHER PLANE (Bureau to.) (Type) (Init assigned to) 
_ Tm of OPERATION 
□ LARD BASED OPERATIONS CONTINENTAL □ FORE I OR □ RESERVE PRO MAN □ TRAINING COMftRO (ImcIwNIh« rairoabar) □ CARRIER OPERATIONS 
r REPORT FILED BY (Signature) (Printed name) (lank) (late) 
PART II. INJURY CORRELATIONS 
(AMSWEH ALL of the following, even if opinion or estimate} 
l"LIST PRECAUTIONS TAKEN IN ATTEMPT TO PREVENT, OR LESSEN DEGREE OF INJURIES. (Outline briefly »Aether successful or not.) 
2. WHAT SAFETY DEVICES WERE UTILIZED? (List failures to utilise, or failure of safety devices, and how these failures contributed to the injuries.} 
J~. WHAT SPECIFIC PARTS OF THE AIRCRAFT CAUSED THE INJURY? LIST AND DESCRIBE, (intries of "no”, -none", •sustained on impact", "undetermined’, with no amplifying 
remarks and opinions will not be accepted.} 
A. 9. REASON PILOT DIDN’T SAIL OUT 
□ •AIL OUT □ ATT onto BAIL OUT □ EJECTION SEAT USED □ SHOULD NAVE BAILED OUT ITT DIDN'T 
8. ALTITUDE OF PLANE AT TIME OF EXIT 7. ATTITUDE OF PLANE AT TIME OF EXIT (if spin, type 8K directionj 8. SPEED OF PLANE AT TIME OF EXIT 
KNOTS 
• , APPROX. ALTITUDE. PILOT LEFT EJECTION 10. APPROX. ALTITUDE, RIPCORD MAS PULLED 11. APPROX. ALTITUDE, CHUTE OPENED 12. HAS FREE FALL DEL IBERATE 7 
FT. FT. FT. □ YES □ » 
1). WAS OXYGEN USED DURING DESCENT? IF SO WHAT TYPE EQOIPICNT? 1*. METHOD OF EXIT (eucept in ejection seat) 15, DID PILOT RAIL OUT TOO LOW FOR CHUTE 
D..t Dun I □« 
18. LIST PERTINENT FACTS PERTAINING TO ITEM 2 ABOVE. 17. LIST CAUSE OF INJURY AS PERTAINING TO ITEM 3 ABOVE. 
18. LIST ANY DIFFICULTIES EXPERIENCED AND/OR REMARKS ON ADDITIONAL SHEET. 1*. SUBMIT PILOTS NARRATIVE OF ENTIRE EVENT ON ADDITIONAL SHEET. 
BAIL OUT DATA 
PART III. PILOT DATA 
l!" HM MARY PREVIOUS ACCIDENTS MAS PILOT BEEN INVOLVED IN. WHILE IN ACTUAL CORTROL OF AIRCRAFT* 
7! ARE THERE AMY INDICATIONS THAT THE PILOT MAY HAVE BEER SUFFERING FROM SOME PHYSIOLOGICAL ANNORNALITV. (bonds, outo-kinssis, blackout, tic.) AT TIME OF ACCIDENT? 
y ARE THERE ARY IRDICAT IONS THAT THE PILOT MAT NAVE REEH IM POOR PHYSICAL COROITIOR (illnsss, lock of sleep. recent over-indulgences. use of medicines. tie.) AT TI ME 
OF ACC I DEBT 7 
A. ARE THERE ART IROICATIORS OF URUSUAL MERTAL COROITIORS (anxiety, Door adjustment, previous narrow escapes, «»C.J EXI ST INC PRIOR TO TNIR FLIGHT? IF SO OUTLIRE 
RRIEFLV. 
WAS THE SITUATION CORFRORTING THE PILoV AT TIME OF ACCIDENT IR ART RAY UNIQUE (unusually heavy traffic, distracting'stimuli, recant narrow escape in similar 
circumstances, ete.fi IF SO* OUTLIRE RRIEFLT. 
I. PILOT ERROR fckmck appiicmblm block) 
□ JU 000*011 
□ TECHNIQUE 
□ VIOLATION 
7. LIST SPEC IF 1C PILOT ERRORS (DO DOT ms I if* parcsmtagmi) 
Figure 12-7.—Medical officer's report of aircraft accident. 
224 Chapter 12. — OPERATIONAL PROBLEMS IN AVIATION MEDICINE 
AVIATION CIRCULAR LETTERS 
PART IV. PERSONNEL INJL RED (PLANE OCCUPANTS ONLY) 
I. Under HAMSS AMD DESIGMATIOM MOs. OF IMJURSD PSRSOMMEL. list sur- 
name followed by initials. IM ALL IM5TAMCES. MiETMSR IMJURSD OR 
UMIMJURBD. LIST PILOT IM MUMMER 1 P05ITI0M. 
a. At all other points on tAto form, each of the injured shall be 
designated merely hy the nmssber to tAo left of his name in the 
listing below. 
5. Use additional sheets as necessary, filling separate form for 
each aircraft where tn were injured. 
4. Under RARE OR RATES, if Reserve, ototo Volunteer (mfm). Organised 
CO'). Active Duty ("A"), or Active Duty Training Cruise folun- 
teer ("TT*), or Organised COT'). 
5. Under IMJURY CLASS., use following hey (M.A.C.A. standard with 
odd it tons;) 
Class 'A' - Injuries resulting in doatA within 90 days. 
DIRECTIONS 
Class - Serious injuries, including unconscions ness, frac- 
tures except simple of fingers and toes, lacerations 
involving muscles or causing severe hemorrhage. in- 
jury to internal organs, or any other injury which 
will Probably incapacitate for 5 or more days. 
Class - All minor injuries. 
Class 'Lm - Missing and presumed dreamed. 
Clast *#* - Missing. 
MOTE: Later necessary changed from T, to *i* the ninety day 
Period should be forwarded if hnotm. 
6. Under DISPOSITIOt. use following hey: 
mD' Uninjured. 
mM' Treated and returned to duty without hospitalisation. 
"I" Hospitaltsation. 
T* Autopsy performed. 
'I' Ream ins to morgue without autopsy. 
SERVICE NUMBER 
RANK OR RATE 
"d'u'Ty aboard 
PLANE 
(OR ON GROUND) 
NAMES AND DESIGNATION NOs. 
OF INJURED PERSONNEL 
AGE 
POSITION OCCUPIED IN PLANE 
AT Tll€ OF ACCIDENT 
INJURY 
CLASS. 
DISPO- 
SITION 
TOTAL BUMCR AOOtriOKAL. UIIKJUM& XCUFRtTS 
PART V. SUMMARIES CF INJURIES (PLANE OCCUPANTS ONLY) 
1. Summarise all Personnel injuries by placing designation numbers 
assigned in part If in appropriate squares (e.g.. if the Pilot 
suffered severe shock, cerebral concussion and severe lacerations 
of head, a small figure "1* should be placed in all pertinent 
squares.) 
3. If injuries are multiple extreme, list all major injuries. 
DIRECTIONS 
3. Rhere injuries were fatal, indicate Probable cause of death by 
placing an T* after number tn the Pertinent square (e.g., \f Ho. 
3 were billed having suffered a cranial fracture and mild contu- 
sions of the trunk, an *X" shmld be placed after the ma" under 
CRAMIAL FRACTURF. 
4. Remarks and suggest ions are encouraged. 
SHOCK MILD I MODERATE | SEVERE 
UNCONC IQUSNESS SHORT OURAT IQN-L I TTLE SIGNIFICANCE OTHER 
r DEGREE 1ST 2ND 3RD 
S CARBONIZATION 
S AREA HEAD AND NECK TRUNK EXTREMITIES ENTIRE BODY 
CEREBRAL MINOR FACIAL MAJOR FACIAL 
HEAD CONCUSSION INJURIES INJURIES 
"UURIES UNO* eye °"€ m 
INJURIES BOTH EYES INJURIES BOTH EYES 
FRACTURES 
TYPE SKULL VERTEBRAE r pEL_ U. ARM L. ARM HAND U. LEG L. LEG FOOT 
BONES c»A»|Al FACIAL CEtV. TMOt. LUH. SAC. COC. VIS LFT. tT. LFT. tT. LFT. tT. LFT. tT. LFT. tT. LFT. tT. 
SIMPLE 
COMPOUND 
OTHER 
AREA OF LACERATIONS CONTUSIONS ABRASIONS 
INVOLVEMENT MILO MODERATE SEVERE MILO MODERATE SEVERE MILO MODERATE SEVERE 
HEAD AND NECK 
TRUNK 
EXTREMITIES 
AMPUTATIONS 
ARM FOREARM HAND FINGERS LEG LOW. LEG FOOT TOES 
TYPE HEAD 
LFT. tT. LFT. tT. LFT. tT. OOl MORE LFT. tT. LFT. tT. LFT. IT. ORC MORE 
TRAUMATIC 
SURGICAL X X X X X 
INTERNAL INJURIES (SUMMARIZE IF AUTOPSY WAS PERFORMED) 
REMARKS 
7^^=SS=====T^T^== A ftp IT IQNAL SHEETS RELATIHG TO THIS AC.C. IDFHT ARE ATTAfHEn O.-.C-jS-li 
Figure 12-8.—Medical officer's report of aircraft accident. 
225 AVIATION MEDICINE PRACTICE 
injuries—both serious and fatal—are caused 
by the placement and design of certain objects 
and structures. 
Investigations of internal injuries in per- 
sonnel who have been subjected to large forces 
for short duration in military-aircraft accidents 
have been made by Haas. Although he placed 
emphasis on the extent and nature of these in- 
juries, he concluded that the prevention of in- 
juries can best be achieved by determining 
which parts of the aircraft are responsible for 
contact injuries, to what extent structural col- 
lapse is involved, and how adequate the provi- 
sions for emergency exits were. 
In many crash landings the airplane is not 
stopped immediately on impact but often skids 
along the ground before coming to rest. When 
the angle of impact is large and the ground 
soft, penetration of the airplane into the ground 
for a measurable distance tends to absorb the 
shock. Even when the surface is more solid, 
the motion is checked less abruptly because of 
the telescoping of the aircraft structure. Thus, 
even under extreme conditions, the collapse of 
the fuselage in the proper direction can go 
far to reduce the decelerative forces on the 
passengers and the crew. The aeronautical en- 
gineer can contribute to survival in marginal 
accidents by a design in which the crew or the 
passengers are in a fairly rigid inner structure 
surrounded by supporting members which, as 
they are crushed, will reduce the force on the 
cockpit or cabin itself. 
Studies of accidents have shown that seats 
of light construction often increase the severity 
of the injury either by collapsing under down- 
ward pressure or by tearing loose when the 
horizontal deceleration is great. In a number 
of cases where belt fastenings have held under 
the impact, the seats have been torn loose and 
thrown forward with disastrous results to the 
occupants. 
The importance of a proper distribution of 
forces between the body and the supporting 
structure has been brought out in reports of 
survival in aircraft accidents. Standard ditch- 
ing procedures in the services recommend (1) 
a seated position facing the tail of the plane 
with the knees drawn up and with the head 
and back braced against a solid structure, or 
(2) a prone position on the floor with the head 
to the rear, knees slightly bent, and feet firmly 
braced against a solid structure. The passenger 
who is riding in a seat facing backwards to 
the forward movement of the plane stands a 
better chance of escaping injury because the 
impact forces are more widely distributed over 
the body. If local injury to the neck is to be 
prevented, the head must be supported by a 
headrest or the back of the seat. There are 
various obstacles to be overcome in achieving 
backward seating in air transports; the opera- 
tors hesitate to include such an arrangement 
in their specifications for fear of popular disap- 
proval. Some designs, however, have provided 
seats facing alternately backward and forward. 
The use of tricycle landing gear has eliminated 
the passenger’s tendency to slide off the seat— 
which is one of the main obj ections to backward 
seating—by maintaining the fuselage in a 
horizontal position when the airplane is on the 
ground. Some of the usual objections to riding 
backward on a railway coach or bus are not 
present in flight because of the absence of a 
sense of motion and of reference objects in the 
immediate field of view which create disturbing 
reactions chiefly of a visual nature. In so far 
as these psychological responses of the pas- 
senger during flight are concerned, there is 
nothing to prevent reversing the conventional 
direction of seating. 
Oxygen installations.—The wide experience 
with nonpressurized planes at relatively high 
altitudes obtained by the military services dur- 
ing the World War II has afforded many 
graphic instances of fatalities and near fatali- 
ties that have occurred either because of faults 
in the system or because of inadequate indoc- 
trination and operating procedures. Oxygen 
want would not present a major problem on 
pressurized planes, however, unless there were 
a failure in the supercharging system or the 
cabin structure. 
Advance analysis of faults in airport design. 
—Another aspect of aviation deserving atten- 
tion is the extent to which the design of air- 
ports may be a factor contributing to accidents. 
In so far as accidents are concerned, some of 
the more important considerations for airports 
are as follows: (1) the length of the runways 
should be adequate (a) to handle the most ad- 
vanced type of equipment with wide margins 
226 Chapter 12. — OPERATIONAL PROBLEMS IN AVIATION MEDICINE 
of safety and (b) to permit the aircraft to roll 
safely to a stop in the event of engine failure 
at the point where its wheels lose contact with 
the ground during take-off. (2) The runways 
must be able to withstand the impact and fre- 
quent use of large aircraft. (3) Because of the 
increasing wing span, it is important that the 
width of the runway permit considerable lee- 
way for maneuvering or yawing in the event 
of the loss of an engine to avoid striking other 
aircraft or obstacles or going off the runway 
onto a soft shoulder. (4) Attention should be 
given for surface drainage in the tropics and 
snow removal in the temperate and northern 
regions. (5) The location should be selected 
with regard to the presence of obstacles such as 
hills, embankments, trees, radio towers and 
tall chimneys that cannot be easily removed. 
(6) A careful study should be made of the 
prevailing winds in relation to the direction 
and layout of the runways. (7) The design 
and layout of the lighting facilities should be 
studied in relation to their effect on the pilots 
as well as their value for ground personnel. 
Advance analysis of personnel failures.— 
After each transport accident an attempt is 
always made to allocate the causes or place 
the responsibility on some definite factor such 
as the pilots, other personnel, the aircraft, the 
ground and navigational facilities, or the regu- 
lations governing the operations. Each of the 
interests represented naturally tries to establish 
its lack of responsibility for the crash. In a 
number of cases those responsible for the per- 
formance of the equipment tend to place the 
blame on personnel failure, while the air crews 
often feel that too much has been expected of 
them or the operating conditions were unfavor- 
able. The reconstruction of what happened dur- 
ing the crash by a post-accident analysis is 
subject to many errors and is often complicated 
by the efforts of these various groups to pro- 
tect their special interests. In general, both 
the pilot and the airplane, and often others, 
are involved in each crash and no one can.be 
completely relieved of some responsibility. If 
the aim is to prevent accidents, it would ap- 
pear to be more reasonable to raise the ques- 
tion as to what can be done to improve the 
equipment in relation to procedures involving 
the human element. 
The majority of accidents in the past have 
been attributed to human error of two general 
types. The first, which is rarely encountered 
in air operations, includes those resulting from 
recklessness or gross negligence on the part 
of the air crew. It is assumed that this type 
will be eliminated either by more careful selec- 
tion or by better training and improvement 
in morale. The more important group com- 
prises those resulting from errors of judgment 
or of technique; it is this type with which we 
are concerned here. Where judgment or tech- 
nique is concerned, sooner or later a particular 
pilot encounters a set of circumstances with 
which he is unable to cope, and under tension 
of the setting he becomes involved in an acci- 
dent. Even the most highly skilled personnel 
may be presented with a problem so difficult 
that the chance of error becomes very great. 
For this reason it is felt that planes should 
be designed for the average pilot rather than 
for the most capable pilot, providing wide 
margins of safety for each contingency that 
might arise. 
The location and inadvertent use of controls. 
—The importance of separating certain essen- 
tial switches or controls and of having guards 
prevent their being manipulated inadvertently 
or prematurely has been demonstrated repeat- 
edly in operating experience with both civilian 
and military aircraft. Frequent confusion has 
occurred between landing gear controls and 
tail-wheel locks or flaps when constructed simi- 
larly and located adjacent to each other. 
Confusion in reading or in setting instrument 
dials.—It is well recognized that a pilot usually 
has little difficulty in reading each instrument 
when time is not a vital factor. In most critical 
situations, however, the indications from many 
instruments must be comprehended quickly and 
more or less simultaneously. If an error is 
made under such circumstances the question 
may be raised as to whether the design or the 
pilot was at fault. Thus the instrument panel 
should be so arranged as to prevent the pos- 
sibility of confusing one instrument with an- 
other. 
Illusions from identification lights, instru- 
ments, and controls.—The role of illusions, 
especially those of spatial orientation, is thor- 
oughly recognized and stressed in pilot-training 
227 AVIATION MEDICINE PRACTICE 
programs. This source of error, however, is not 
always appreciated in the design of the instru- 
ments and the exterior lighting of aircraft. 
For example, accidents may arise from misin- 
terpretation of identification lights on other 
aircraft because of the autokinetic illusion. 
This visual illusion may be described as the 
tendency of a single fixed point of light to 
seem to move in a random fashion when looked 
at steadily against a dark background. If a 
subject is asked to localize such a source of 
light he will usually state that he cannot do 
so with certainty because the light appears 
to move about. This apparent shifting of a 
light that is actually fixed is known in psycho- 
logical terminology as “autokinetic movement”. 
In laboratory experiments it is not uncommon 
for a mild hypnotic state to be induced while 
steadily observing a small light. In fact, this 
principle has long been used in psychological 
medicine as an aid in inducing hypnosis. 
The existence of illusory phenomena prob- 
lems was recognized in aviation after several 
accidents due to these causes. Pilots have be- 
come involved in difficulties not only while ob- 
serving another plane in flight, but also in 
identifying lights, markings, and fixed struc- 
tures such as bridges and smokestacks. Since 
1941, corrective measures in the form of double 
tailed lights blinking alternately have been 
required by the CAB as a result of an accident. 
The regulations now provide for a light at 
each wingtip and at the top and the bottom 
of the fuselage, approximately in line with 
the forward position lights. In addition there 
must be two alternately flashing lights (one 
red, one white) some distance apart on the 
tail of the plane. This complex light pattern 
tends to destroy the autokinetic illusion and 
enable the pilot to identify with less confusion 
another aircraft in flight at night. The military 
services became more interested in the problem 
during the World War II after several acci- 
dents occured, especially during formation fly- 
ing night. 
Studies both in the laboratory and during 
formation flights at night, as reported by Gray- 
biel and Clark, have shown that the conditions 
favorable to this illusion are (1) a nearly dark 
environment, (2) a small single stimulus of 
low intensity, (3) steady fixation, and (4) 
fatigue, either general or ocular. It is easy to 
imagine how such a set of circumstances in 
aviation may place the pilot in jeopardy. The 
pilot should rely on the instruments if there is 
any doubt or conflict between his perceptions 
and the instrument readings. 
Problems involved in instrument vs. contact 
flying.—It is a well known fact that a high 
accident rate occurs during the changeover 
from contact to instrument flying. In recent 
years, serious accidents have occured, particu- 
larly in approaches and landings at night or 
under adverse weather conditions. Emphasis 
is placed on the problems confronted by the 
pilot in (1) making the transition from one to 
the other in landing and takeoff and (2) 
choosing between contact and instrument flying 
under adverse operating conditions. The pilot 
naturally feels more secure when he is able 
to see outside the plane, even though his view 
may be quite inadequate. For this reason 
pilots often choose to go on contact when a 
more proper procedure would be to use instru- 
ments. 
The importance of night vision in air opera- 
tions.—It is extremely difficult to prove that 
any specific accident or near accident occurred 
solely because of the absence of good night 
vision on the part of the pilot. It is relatively 
easy, however, to select a number of accidents 
in which the probable lack of night vision 
under condition of low illumination at the time 
of the accident is a common factor. The most 
frequently encountered situations in which diffi- 
culty from this source may be expected are as 
follows: (1) on night takeoffs from well illu- 
minated runways, a critical time occurs when 
the end of the runway is reached and the pilot 
goes off contact onto instruments. At that time 
the airman may suddenly be in complete dark- 
ness, he is usually at very low altitude, and 
any other aircraft or obstructions in the vicin- 
ity create real collision hazards. (2) Landings 
at the end of long flights may involve a certain 
amount of risk because the visual efficiency of 
pilots is at low ebb. Simple fatigue may have 
been accentuated by anoxia or carbon monox- 
ide during flight, or the decrease in light sen- 
sitivity due to anoxia may have been intensi- 
fied by low blood sugar resulting from pro- 
longed fasting. (3) The need for good outside 
228 Chapter 12. — OPERATIONAL PROBLEMS IN AVIATION MEDICINE 
Figure 12-9.—How the gyro-horizon appears to the pilot. 
Figure 12-10.—How the pilot must interpret his gyro- 
horizon. 
visual aids is particularly important at twilight 
or night levels of illumination. Poorly lighted 
airports present obvious dangers during land- 
ing and takeoff procedures, but even during 
cruise it may be necessary for the pilot to look 
outside the plane to observe other aircraft or 
meteorological conditions such as clouds and 
storms which can be by-passed, terrain and 
mountains if the plane is blown off its course, 
or important landmarks, groundmarks, ships 
at sea, and other piloting and navigating aids. 
(4) On large aircraft the lighting of the control 
cabin is not usually designated for maintaining 
the dark adaptation; if the pilot in the course 
of his duties leaves the cockpit to visit one of 
the other stations he may destroy his ability to 
see under low illumination. Such a loss of 
night vision would seriously handicap him in 
returning to the controls should an emergency 
occur. Occasionally there is no provision for 
light traps to keep the bright lights in the 
control cabin from influencing the pilots in the 
cockpit. 
Disorientation caused by misinterpretation 
of the gyro-horizon.—Any circumstance which 
decreases a pilot’s ability to localize his position 
or attitude in space can be considered a cause 
of disorientation. Misinterpretation of the gyro- 
horizon, which occasionally occurs, causes dis- 
orientation and crashes. 
It takes several hours to teach a pilot to 
interpret the gyro-horizon. When he uses the 
instrument for the first time, the horizon 
indicator appears to move as he banks his 
plane, while the little plane on the instrument 
appears level, since its wings always maintain 
the same relative position to him — at right 
angles to his longitudinal axis. (See figure 9.) 
He must be taught that the horizon indicator 
remains in a fixed position with respects to the 
actual horizon while the little plane on the in- 
strument and the plane he is flying revolve 
around it, as shown in figure 10. 
Occasionally a pilot who has stared intently 
at the instrument panel during an instrument 
flight becomes the victim of a reversal of per- 
ception. He perceives the horizon bar tilting 
rather than himself tilting with respect to the 
horizon. When he is making a turn to the left, 
he sees the horizon bar tipped to the right as 
shown in figure 9 and endeavors to level with 
respect to himself by lowering his left wing. 
If his angle of bank to the left then becomes 
steeper, and his nose drops, a graveyard spiral 
may result. The chances of this mistaken per- 
ception occurring are increased if he has been 
under a strain for a long time and fatigued. 
229 AVIATION MEDICINE PRACTICE 
QUESTIONS 
1. Briefly outline the general organization of an 
ideal air sea rescue operational organization. 
2. Briefly describe the important characteristics of a 
good rescue seaplane. 
3. List the different types of rescue craft used in 
air sea rescue, 
4. What procedures should be instituted in order 
to keep water loss at a minimum in tropical ocean areas 
while on a liferaft? 
5. Name three methods of producing drinking water 
from sea water. 
6. Briefly describe a “Solar Still”. 
7. Briefly describe the emergency ration now used 
in Navy liferafts. 
8. What is the reason for “screening” patients prior 
to a hospital flight? 
9. What type patients are generally not adaptable 
for air transportation? 
10. Briefly describe the different methods of acci- 
dent analysis and prevention. 
11. When is the Naval Medical Officer Report of 
Aircraft Accident submitted? 
12. Briefly discuss illusions from identification 
lights. 
13. Briefly discuss the importance of night vision 
in air operations. 
14. Briefly discuss disorientation caused by misin- 
terpretation of the gyro-horizon. 
BIBLIOGRAPHY 
1. Head, Air Sea Rescue Agency, The Air Sea 
Rescue Manual, 20 June 1945. 
2. Bureau of Naval Personnel, Handbook of Survi- 
val in the Water, NavPers 16046, 1947. 
3. BuMed News Letter, “Aviation Supplement,” Vol. 
5, No. 1, 6 July 1945. 
4. McFarland, Ross A. Ph.D., Human Factors in 
Air Transport Design, 1946. 
5. Air-Sea Rescue Agency, Air Sea Rescue Bulletin, 
July 1944. 
6. Air-Sea Rescue Agency, Air Sea Rescue Bulletin, 
Oct. 1944. 
7. Air-Sea Rescue Agency, Air Sea Rescue Bulletin, 
Dec, 1944. 
230