PRIZE ESSAY OE THE ALUMNI ASSOCIATION 
OF THE 
College of Physicians and Surgeons, 
NEW YORK, 1873. 
THE EFFECTS 
OP 
HIGH ATMOSPHERIC PRESSURE, 
INCLUDING THE 
CAISSON DISEASE. 
By ANDREW H. SMITH, M. R, 
Surgeon to the New York Bridge Company, 
Member of the Academy of Natural Sciences, Philadelphia; 
Corresponding Member of the Gesellschaft fur Heilkunde, 
Berlin; late of the Medical Staff of the Regular' 
Army ; Surgeon to the Throat Department of thS 
Manhattan Eye and Ear Hospital ; Physician 
to St. Luke’s Hospital, etc. 
BROOKLYN: 
EAGLE PRINT, 34, 36 and 38 FULTON STREET. 
1873. REPORT 
ON 
THE EFFECTS OF HIGH ATMOSPHERIC PRESSURE, 
INCLUDING THE 
CAISSON DISEASE. 
By ANDREW II SMITH, M. D., 
Surgeon to the Company. 
To the Board of Directors of the New York Bridge Company : 
Gentlemen :— 
This Report was originally intended simply to present my own ex- 
perience as Surgeon to the New York Bridge Company during the 
sinking of the second caisson. But in endeavoring to compare this 
experience with that of others who had had opportunities of observ- 
ing the effects of high atmospheric pressure, I found that the litera- 
ture of the subject consisted only of isolated reports by different 
individuals, in different languages, and having little or no reference 
one to another, so that a great deal of research was required to obtain 
a connected view of the subject. It seemed to me, therefore, de- 
sirable not to add another to the list of disjointed fragments, but 
rather to incorporate my own observations with the existing mate- 
rial, and thus present in one view a resume of our actual knowledge 
upon the subject. This I have endeavored to do briefly in the follow- 
ing pages. For whatever is purely theoretical, however, and espe- 
cially as regards the pathology of the Caisson Disease, I must accept 
the entire responsibility, unless reference is made to other authority. 
CHAPTER FIRST. 
The discoveries of Torricelli, in 1643, which led to his invention of 
the barometer, and the further elucidation by Pascal of the principles 
of atmospheric pressure, five years later, were followed by confused 
and contradictory speculations on every hand as to what would be 
the effect upon animal life if the barometric changes so eagerly 
observed assumed a wider range. 
Dr. Henshaw, an English physician, published an essay in 1664, in 
which he proposed to treat diseases by varying the pressure of the 
atmosphere by which the patient was surrounded. His idea was to 
have a room (domicilium) constructed of masonry, and made air- 
HISTORY. 4 
tight, in which the sick person could remain in an atmosphere which 
was to be either rarefied or condensed by the action of an organ 
bellows. 
He fancied that acute diseases would be benefited by an increased 
pressure, while chronic diseases on the other hand demanded a rare- 
fied atmosphere. His views seem, however, to have been purely theo- 
retical, as there is no record of any serious attempt to reduce them to 
practice. 
More than a century elapsed before the subject again awakened the 
attention of scientific men. In the year 1788 the Academy of Sci- 
ences of Haarlem offered a prize for a description of the best appara- 
tus for experimenting upon the effects of compressed air, with a 
record of experiments made by means of it on animal life, the growth 
of plants, and the inflammability of the different gases. This 
prize, however, was not contended for until more than half a century 
later. 
Diving-bells were brought into use as early as the beginning of the 
sixteenth century, but the condensation of the air within them does 
not seem to have attracted attention, at least as affecting the occu- 
pant. Indeed, whatever influence the increased pressure may have 
exerted wras masked by the impurity of the air, which, in the ma- 
chines first employed, was not renewed. It was found that the 
strongest man could not remain under water longer than an hour; but 
the ill effects experienced were attributed to the heat which accumu- 
lated in the bell, and which was supposed to affect respiration. Sub- 
sequently, when an apparatus was added for supplying fresh air, it 
was remarked that the workmen felt no inconvenience whatever. 
The first observations of real value upon the effects of high at- 
mospheric pressure were made at Howth, near Dublin, in the year 1820, 
by a distinguished Russian physician named Hamel. In the course of 
some engineering work in which diving-bells were employed, Dr. 
Hamel had the opportunity of studying the effects of compressed air, 
not only upon the workmen, but also upon himself. In describing his 
own experience, he states that at the depth of five or six feet severe 
pain was felt in the ears, which was relieved in a measure by swal- 
lowing. At fifteen or sixteen feet, there was a noise in the ears like 
an explosion, followed by entire relief from the pain. His respiration 
was perfectly easy. 
The ascent was accomplished with much less inconvenience than 
the descent. 
Hamel states that one of the workmen became so accustomed to 
the air of the bell as to be uncomfortable under the usual atmospheric 
pressure.* 
* Bibliotheque de Geneve, 1820. 5 
In 1826, Dr. Collation published observations made at the same 
time and place as the above. In winter the hours of work in the 
bells were five daily ; in summer, five and ten alternately. Toward 
the close of the work, each day the men became very much exhausted, 
and were given a little brandy and a bit of bread. Those newly em- 
ployed suffered with pain in the head and ears, and were often 
affected with colic and diarrhoea, which last were attributed to cold 
and wet. Increase of appetite and augmentation of the urine were 
observed. In some cases, deafness was relieved, and one case of 
asthma was entirely cured. 
In 1835, Junod published the results of extensive experiments upon 
compressed air as a remedial agent.* This was the beginning of a 
series of memoirs upon this subject appearing in rapid succession in 
France and Germany. Institutions sprang up in various parts of the 
Continent designed to afford the most approved facilities for this 
mode of treatment, and the results obtained were, and continue to 
be, highly satisfactory. The “compressed air-baths” are especially 
useful in the treatment of pulmonary diseases and of dyspepsia. 
But as the pressure employed in these baths is comparatively slight, 
usually not more than eight or ten pounds to the square inch, the 
effects observed differ widely from those produced by the high pres- 
sure employed for engineering purposes. This difference is not only 
in degree, but also in kind, and therefore the literature relating to 
compressed air as a remedy,t although rich, and in itself very in- 
teresting, throws but little light upon the subject of this discussion. 
It is probable, however, that the investigations in this direction of 
Junot, Tabarie, and Pravaz first suggested the employment of com- 
pressed air as a substitute for pumps in mining operations. 
To M. Triger, a French engineer, belongs the credit of first con- 
ceiving and carrying out a plan by which atmospheric pressure was 
made to keep back the water flowing into a mining shaft. It had 
long been known that the valley of the Loire was underlaid by an ex- 
tensive bed of coal, but, inasmuch as in order to reach the coal it 
wTas necessary to pass through twenty metres of quicksand in commu- 
nication with the water of the river, the engineering difficulties had 
been considered, until the advent of Triger, as insurmountable. To 
keep a shaft dry by pumping was equivalent to pumping out the 
Loire. To meet this difficulty, Triger conceived the idea of sinking 
an iron tube through the quicksand, the interior of the tube being 
kept free from water during the excavation by condensing the air in 
* Archives Oenerales de Medicine. 
t Those interested in this subject will find it exhaustively treated in an admira- 
ble work by Dr. Rudolf v. Vivenot; “ Zur Erkenntniss der Physiologischen Wir- 
kung und der Therapentischen Anwendung der Verdichteteu Luft.” Erlangen, 
May, 1812. 6 
the tube to the point of counterbalancing the pressure of the water. 
After some preliminary experiments made by the aid of Tabarie’s 
remedial bath, the work was begun in 1839, near Chalonnes. A tube 
of iron, seventy feet long by three and one-half feet in diameter, was 
provided, with a box or chamber at the top, such as we now call an 
air lock, having a valve above opening' inward, and another below 
opening downward into the tube. These valves were of such a size 
as to permit the passage of the workmen, and the removal of the ex- 
cavated material. The workmen having passed into the lock, the 
upper valve was closed, and a cock opened communicating with the 
main tube, where the air was compressed sufficiently to keep back 
the water, the compression being effected by means of condensers 
worked by steam. The pressure in the lock having become equal to 
that in the main tube, the lower valve was opened and the workmen 
descended into the tube. In going out, or in sending out material, the 
process was reversed. The tube was forced down into the earth in 
proportion as the workmen excavated at the bottom. 
It will thus be seen that the first attempt at this mode of woi king 
embraced all the essential features of the method as now employed. 
In his undertaking, Triger was completely successful. The quick- 
sand was passed and the coal reached, and at the same time there was 
given to the world a new engineering resource of exceeding value. 
It is much to be regretted that these operations were not carried on 
under the eye of a competent medical observer. The only report we 
have of them is by M. Triger himself,* and it is natural that the en- 
gineering rather than the medical aspect of the question should prin- 
cipally engage his attention. His notice of the effects of the com- 
pressed air upon the workmen is extremely meagre, and is summed 
up in the following points : 
‘'1. At the pressure of three atmospheres it is impossible to whis- 
tle, while a lower pressure does not produce this effect. 
“ 2. In the compressed air, every one speaks through the nose, and 
this is the more noticeable the higher the pressure. 
“ 3. All the laborers remarked that in ascending the ladders they 
were much less out of breath (moins essovffl.es) than when mounting 
to a similar height in the open air. 
“ 4. A laborer who had been deaf since the seige of Antwerp, 
(1832,) always heard more distinctly in the compressed air than any 
of his comrades. 
“ No illness was occasioned among the laborers except that two of 
them, after seven hours of labor in the tube, experienced severe pains 
* Comptes Rendues. T. XIII. 1841. “Memoire sur un appareil a air com- 
prine pour le percement des puits, etc. Par M. Triger. 7 
in the arms and knees, coming on about half an hour after ascending 
into the open air.” These are the first recorded cases of what 1 have 
named the Caisson Disease. 
About the year 1850 compressed air was first employed in the 
sinking of piers. A railway bridge was constructed over the Medway, 
between Rochester and Chatham, the piers of which rested on a basis 
composed of hollow iron piles, forty-two inches in diameter, each of 
which was sunk in precisely the same manner as the tube of Triger. 
I have not been able to find any record of the effects of the com- 
pressed air upon the men employed, though some accidents due to 
this cause are stated to have occurred. 
The results obtained by Triger led, in 1845, to the application of 
the same principle to the working of the mine at Doucliy, Depart- 
ment du Nord. The laborers in this case were under the supervision 
of MM. B. Pol and T. J. J. Watelle, who published an extremely in- 
teresting memoir upon the subject.* 
The entire personnel comprised sixty-four men, who were employed 
at two different epochs, under different pressures. They were 
divided into gangs of six or seven each, laboring alternately four 
hours twice a day. At first, the time allowed for locking out was 
one-fourth of an hour, but as the pressure increased it was extended 
to half an hour. The maximum pressure was three and one-half 
atmospheres. 
After each shift the men bathed and put on dry clothes, when a 
cup of bouillon and a glass of Bordeaux were served to each man. 
As the number of cases of illness increased, a sort of ambulance, or 
temporary hospital, was established at the spot. 
At a pressure of two and three-quarter atmospheres, Pol experi- 
enced in his own person the pain in the ears while locking in, and the 
ease with which a ladder is ascended in the compressed air, confirm- 
ing in this latter particular the observation of Triger. The soot from 
the candles with which the air of the shaft was loaded, produced a 
troublesome cough, attended with black expectoration. The mucous 
membrane of the nose and throat became stained with it, and even 
the faeces were blackened. 
While locking out there was experienced by all the men a feeling 
of suffocation. Pol was the first to perceive that the real danger was 
in passing from the condensed into the normal atmosphere, instead of 
in passing in the reverse direction. On emerging into the open air, 
he found that his pulse, which had fallen while in the caisson from 
seventy, its normal standard, to fifty-five, rose suddenly to eighty- 
five. When the pressure had increased to three and one-half at- 
* Memolre sur les Effets de la Compression de Pair, etc. Annales d’ Hygiene 
Publique et de Med. Legale, 1854. 8 
mospheres, he again entered the caisson. The unpleasant sensations 
already referred to were found to be intensified. In blowing his nose 
he accidentally discovered that this operation gave much more perfect 
relief to the ears than the act of swallowing. In speaking he found 
that the tongue moved stiffly and with difficulty. Sounds were not 
heard with their usual intensity. The secretion of urine was decid- 
edly increased. After reaching home he was seized with severe pain 
in one arm and shoulder, and in the walls of the chest. Afterward, 
there were chills, followed by vomiting. Rest in the horizontal po- 
sition, and the use of sudorifics, restored him to his usual health by 
the following day. 
Of the sixty-four men employed, thirty-nine continued until the 
work was completed, and twenty-five were compelled to give up their 
places, not being able to support the effects of the compressed air. 
The most usual affection was muscular pains, occurring either alone 
or ushering in other symptoms. Pulmonary congestion occurred in 
several cases, but it may well be questioned whether the excessive 
impurity of the air, as evinced by the amount of soot it contained, 
may not have had much to do with the production of this otherwise 
unusual result. Other symptoms which he describes, such as great 
hebitude, incoherence of speech, tottering gait, etc., indicate the 
effects of carbonic acid, and as no mention is made of any provision 
for removing the products of combustion and respiration, this gas 
must have been present in considerable quantity. 
The conclusions arrived at by Pol are as follows : 
1. A pressure of four and one-quarter atmospheres is not in itself 
dangerous, but the return into the open air may cause serious acci- 
dents, and even sudden death. The danger is in proportion to the 
previous pressure. 
2. The pathological changes consist in visceral congestions, among 
which congestion of the lungs and brain take the foremost rank. 
3. The tendency to these congestions increases with the age, at 
least between eighteen and fifty-five. , 
4. Not the period of greatest strength, which is between thirty and 
forty, but that between eighteen and twenty-six is that which' is ex- 
posed to the least danger. 
5. Experience teaches that the ill effects are in proportion to the 
rapidity with which the transition is made from the compressed air to 
the normal atmosphere. 
6. Unimportant troubles, such as cough, gastric symptoms, etc., 
may be due to the smoke from the lamps. 
7. The treatment is not different from that which is usual when 
like symptoms arise from other causes. The first indication is to 9 
bring about a reaction, which is in turn to be combatted when it ex- 
ceeds physiological limits. 
8. One case seems to indicate that the quickest and safest means of 
restoration is an immediate return into the compressed air. 
9, Cold to the surface is the best means for restoring the function of 
the skin. 
About the year 1856 this method of excavation was employed in 
the coal mines at Eischweiler, near Aix-le-Chapelle. No phenomena 
were observed differing from those already described, except that 
bleeding from the nose occurred in several cases on emerging into 
the open air.* 
About 1858-9 excavation by the aid of compressed air was exten- 
sively employed in laying the foundations of piers for bridges. 
Among the first of these were the Quarantine Bridge at Lyons, the 
bridge at Macon, and the chain bridge over the Thiess. A report 
upon the latter is contained in the “Annales des Ponts et des Chaus- 
ses,” for 1859. Ringing and pain in the ears were complained of by 
the laborers, as also pain in the teeth, and in the muscles generally. 
The sound of the voice was observed to be changed, and the breath- 
ing to be quickened. The return to the open air was often followed 
by bleeding at the nose. Men of several different nationalities were 
employed, and it was observed that the Hungarians and the French 
suffered least, while the Italians, Germans, and Sclavonians were 
most affected. 
In 1859, the mines at Eischweiler were re-opened, compressed air 
being again employed. The pressure did not exceed two and one- 
half atmospheres. The duration of the shifts was six hours. Exces- 
sive sweating was observed, followed by thirst after leaving the mine. 
There was generally impairment of appetite, t 
At the same time work was being carried on by similar means in 
the coal mines at Luttich. According to the statement of the super- 
intendent, the men became'so emaciated that after a few months they 
could no longer be prevailed upon to continue the work, notwith- 
standing large wages were offered and the most nourishing food 
provided. 
Perhaps the most extensive work undertaken in Europe by the aid 
of compressed air was the bridge over the Rhine, at Strasburg. An 
account of this is given by Dr. Francois, who had medical charge of 
the workmen.! 
* Vivenot. Wirkung der Verdichteten Luft. 
t Ibid. 
I “ Des effets sur les ouvriers travaillant dans les caissons servants de base aux 
piles du Pont du Grand Khin.” Annales d’ Hygiene Publique et de Med. Legale. 
T. XIV. 1860. 10 
The caissons were fourteen in number, each seven metres long by 
five and eight-tenths wide and three and five-tenths high. The 
locks were two metres in diameter and four metres in height. 
Franc;ois refers to the progressive impairment of hearing as the 
pressure increased in the lock ; to the increase of temperature from 
the compression of the air; and to the accumulation of soot in the 
air-passages, which had been before observed by other writers. On 
going out of the caissons, intense pain in the ears sometimes occurred, 
together with muscular and arthritic pains. A very annoying itching 
of the skin was sometimes felt. Cerebral congestions, hoemoptysis, 
and bleeding at the nose, were also not uncommon. Sometimes these 
various affections occurred immediately upon leaving the caisson, 
while in other cases they were deferred for several hours. In two or 
three instances the men were able to walk home, and afterward fell 
“ as if struck by lightning.” The attacks usually passed off quickly. 
Only one death occurred, and that resulted from breaking the rule as 
to the length of time to be occupied in locking out. 
The rule established was to allow from four to five minutes in 
locking out When the pressure was one-quarter to one-half an at- 
mosphere ; six to seven minutes for one atmosphere ; ten for one and 
one-half atmospheres; twelve for two atmospheres. A woolen vest 
was provided for each man to be put on when leaving the caisson, in 
order to guard against the effect of the sudden reduction of tempera- 
ture which resulted from the expansion of the air in the lock. It was 
observed that the foremen suffered much less than the laborers, since 
their superior intelligence enabled them to realize the necessity of 
observing the rules. 
Some other points observed by this writer will be referred to here- 
after in their proper connection. 
In the year 1863, Dr. Antoine Ed. Foley published a monograph 
comprising his observations upon the effects of condensed air as 
demonstrated during the sinking of the piers for a bridge at Argen- 
teuil.* The original work not being accessible, I avail myself of the 
resume contained in the treatise of Vivenot, of which I give a some- 
what condensed translation from the German. 
Foley observes that during the time that the pressure was increas- 
ing, the organs of hearing wrere always, without exception, affected. 
Occasionally neuralgic pains wTere felt darting through the forehead, 
the nasal cavities, and the jaws; the voice acquired a metallic 
sound; whistling became impossible ; in a few cases stammering was 
induced. Taste, smell, and the sense of touch lost their acuteness. 
There was experienced a sense of warmth in the skin, as if one were 
* “ Dii travail dans s’air comprime, etude medicale, hygienique et biologique 
faite au pont d’Argenteuil.” Paris, 1863. 11 
in a drying-room. The pulse became small and thready, sometimes 
imperceptible to the touch. The venous blood had a bright red hue. 
The lungs seemed to increase in development, while the motion of 
the ribs was less. Shortness of breath was not often observed. In- 
crease of appetite was soon experienced, but never thirst. 
While the pressure remained stationary, all subjective phenomena 
disappeared, to return again during the locking out. Ringing of the 
ears and bulging of the ear drums were observed ; taste and smell re- 
turned ; a prickling sense of warmth was felt in the nostrils, which 
was sometimes followed by bleeding at the nose. At the same time 
the rapid decline of the temperature from the expansion of the air 
caused extreme chilliness. 
At first the laborers remained in the compressed air four hours at a 
time, twice a day, with an interval of rest. But as the pressure in- 
creased it was found necessary to diminish the hours of labor. 
The ill effects upon the workmen were almost entirely confined to 
a distressing itching of the skin and painful congestive swelling of 
the muscles. They observed that the appetite was increased while 
thirst was diminished. The flow of urine was also greater than 
usual. 
A remarkable case is mentioned, in which a man, far advanced in 
consumption, with an enormous cavity in one lung, and suffering 
from hectic, persisted in working in the caisson, contrary to the 
advice of Foley, and at the end of two months had gained very 
much in flesh, was looking well, and feeling in the best of health. 
I shall have occasion hereafter, when treating of the Caisson Dis- 
ease, to refer more in detail to some of the experiences of this writer. 
In the year 1868 there was begun at St. Louis a work which 
involved the application of compressed air on a scale far exceeding 
anything before attempted. This was the sinking of two piers and 
two abutments for a bridge across the Mississippi. The magnitude 
of the work consisted iD the great depth to which it was necessary to 
sink the caissons, in order to obtain a solid foundation. One of them, 
at the moment when it touched the rock, was 110 feet below the 
surface of the water. This implied a pressure within the caisson of 
50 lbs. to the square inch. The dimensions of the caissons, too, far 
exceeded those of any before constructed, the average superficial 
area being about 3,700 square feet. 
A large number of workmen were employed, and an opportunity 
was presented for studying the effects of compressed air upon the 
human body on a scale which dwarfed all former experien ces into 
comparative insignificance. 
The physician in charge was Dr A. Jaminet, whose report is 
extremely interesting.* It describes a number of valuable experi- 
* Physical Effects of Compressed Air. St. Louis, 1871. 12 
ments upon the boilhig point of water at various pressures, electri- 
cal phenomena, etc., and proceeds to detail the physiological action 
of high atmospheric pressure as demonstrated upon himself and 
others. The writer then gives his own experience in an attack of 
paralysis resulting from a prolonged sojourn in the caisson—a paraly- 
sis from which he fortunately recovered by the following day. 
He next discusses the mode in which the pressure acts to bring 
about the morbid phenomena observed, and arrives at the conclusion, 
which the facts do not seem to me to warrant, that the ill effects 
are simply the result of exhaustion from too rapid tissue-change, 
caused by the absorption of an excess of oxygen. Following out 
this idea, he lays down a plan of treatment which consists simply of 
rest in a recumbent position, with the feet elevated, and the adminis- 
tration of stimulants and nourishment. 
He describes, more or less in detail, seventy-seven cases, in eight of 
■which death took place. The post-mortem appearances in these are 
described. They were all characterized by congestion of the brain 
and cord, and of most of the abdominal viscera. 
Dr. Jaminet’s observations are exceedingly valuable ; but some of 
his conclusions seem to have been arrived at without sufficient 
thought. It is especially to be regretted that his theory of exhaus- 
tion, framed at the outset, prevented the trial of remedial plans other 
than the routine administration of stimulants and beef-tea. 
The facts observed by Dr. Jaminet will be frequently referred to 
in the following pages, care being taken to give him credit for all that 
had not been anticipated by others. 
CHAPTER SECOND. 
THE NEW YORK CAISSON. 
Before the St. Louis Bridge was projected, a much more gigantic 
work had been inaugurated at New York, and plans and specifica- 
tions had been adopted which anticipated the leading features of the 
work at St. Louis. To cross a stream 1,600 feet in width with a 
single span was an idea never before entertained. But the difficul- 
ties were immensely increased by the fact that the towers to support 
this immense structure had to he erected under circumstances that 
rendered the usual methods for sinking piers impracticable. It was, 
therefore, determined to employ the method by compressed air, and 
caissons were constructed having the horizontal dimensions of the 
proposed piers, which, on the New York side, were 102 by 172 feet. 
Each caisson was in effect a wooden box turned bottom upward, the 
interior space being 9 feet high. The roof of the New York caisson 
(bottom of the box) was 22 feet thick, of solid timber bolted tp- 13 
getlier, and was supported by frames running from side tu side, which 
frames, together with the edges of the box, were to sustain the vast 
superincumbent weight, aided by the upward pressure of the con- 
densed air within the caisson. The area of the structure was equal 
to seven building lots of 25x100 feet each 
The caissons having been built on ways, were launched in the same 
manner as a ship, and were towed to the points where the piers were 
to be located. Courses of granite blocks were then laid upon the top 
of the caisson, by which it was sunk until it rested upon the bed of 
the river. Air was then forced into the chambers beneath by means 
of engines upon the shore, until the water was entirely displaced, 
and the river-bed left dry. The pressure was maintained at this 
point, the engines working day and night. The workmen obtained 
access to the chamber by means of two shafts which extended above 
the surface of the water. At the bottom of each shaft were two air- 
locks, which were simply ante-chambers constructed of iron, into 
which the men entered from the shaft, and, closing an air-tight door 
behind them, admitted the compressed air from the caisson by means 
of a cock, until the pressure in the lock reached the same degree as 
that in the caisson, when a communicating door was opened, and the 
men passed into the chamber below. In going out, the process was re- 
versed, the compressed air in the lock being allowed to blow off 
through a cock into the open shaft. The control of these cocks was 
intrusted to men detailed exclusively for that work, and upon their 
proper management depended Lthe comfort, if not the life, of every 
one in the lock. 
By a very ingenious arrangement, which it is not necessary to de- 
scribe here, the earth excavated from beneath the caisson was car- 
ried up to the surface without affording opportunity for the air to es- 
cape. In this way the earth was being constantly removed from un- 
derneath the caisson, and the vast mass settled day by day down 
through the gravel and quicksand, which formed the bed of the river, 
until at a depth of 78 feet on the New York side, a solid foundation 
was reached. In proportion as the caisson settled the masonry upon 
it was built up, so that the top of the stone-work was always above 
water. When a solid foundation had been reached, the interior of 
the caisson was filled with concrete, and the 400,000 cubic feet of 
timber was left buried nearly 80 feet below the surface, where, prac- 
tically indestructible, it remains as the foundation of the tower. 
Of course the pressure of air required to keep the water out of the 
caisson increased in exact proportion to the depth. Thus, at the 
beginning of the work, the caisson being covered by forty feet of 
water, the pressure was about eighteen pounds to the square inch, 
while at the close of the work it stood at thirty-six pounds. 14 
The air-locks were connected with the surface of the pier by means 
of a spiral stairway within the shaft. Ascending this was found to 
be exceedingly fatiguing as the depth increased, and the stair in one 
of the shafts wras finally replaced by a steam elevator. 
Looking upon it merely from a sanitary point of view, I regard it 
as a serious mistake to have placed the air-locks at the bottom 
instead of at the top of the shafts, as by that arrangement the men 
were compelled to make a fatiguing ascent at the moment when the 
circulation was embarrassed and the system unstrung by the sudden 
removal of the pressure. All testimony is agreed upon the ease, on 
the one hand, with which exertion is supported while in the com- 
pressed air, and upon the unfitness of the system, on the other hand, 
to bear even the slightest fatigue during the period immediately fol- 
lowing the change to the normal atmosphere. These considerations 
should render the rule invariable that the air-lock is to be placed at 
the top of the shaft, unless an elevator is employed. In this view I 
am sustained by all the engineers connected with the work. 
The caisson was lighted by gas supplied by means of a force-pump. 
The combustion of the gas, together with the breathing of the work- 
men, gave rise to the formation of a large quantity of carbonic acid. 
It soon became evident that the amount of air which was required to 
supply the leakage and keep up the requisite pressure was not ade- 
quate to maintain a healthy standard of purity in the air respired. 
This conclusion, arrived at by observation and calculation, was con- 
firmed by trial. A rough, but satisfactory, test was supplied by tak- 
ing a bottle of lime-water into the caisson and passing the air through 
the water by means of an ordinary flexible rubber syringe. It was 
found that a few compressions of the bulb were sufficient to give the 
water a decidedly milky hue. This method has the advantage over 
that employed by Dr. Jaminet, viz., merely shaking an open bottle 
containing lime-water—-that it constantly brings new portions of air 
into contact with the fluid. 
By increasing the number of compressors by which the air was 
supplied, (the excess of air escaping beneath the edge of the caisson,) 
the atmosphere was brought to such a degree of purity as to contain 
only one-tliird of one per cent, of carbonic acid, as I determined by 
actual analysis. This amount of vitiation Avas found not to affect the 
men unfavorably. To maintain this standard, lioAvever, nearly 
150,000 cubic feet of air were required per hour. 
The number of men employed at one time in the caisson varied 
from fifty to one hundred and twenty-five in the day time, and from 
fifteen to thirty during the night. At first the time was divided into 
two “ shifts ” of four hours each, separated by an interval of tAvo 
hours. As the depth increased the hours were reduced, until at last 15 
the two shifts comprised but four hours, divided by a four hours’ 
interval. 
It was not until the pressure had reached about twenty-four pounds 
that any serious effect upon the men was observed. At this time I 
began my daily attendance of from one to three hours at the bridge. 
The first step w as to prepare a set of printed rules, copies of which 
were posted conspicuously. These rules were as follows : 
1st.—Never enter the caisson w ith an empty stomach. 
2d.—Use as far as possible a meat diet, and take warm coffee 
freely. 
3d.—Always put on extra clothing on coming out, and avoid ex- 
posure to cold. 
4th.—Exercise as little as may be during the first hour after coming 
out, and lie down if possible. 
5th.—Use intoxicating liquors sparingly ; better not at all. 
6th.—Take at least eight hours’ sleep every night. 
7th.—See that the bowels are open every day. 
8th.—Never enter the caisson if at all sick. 
9th.—Report at once at the office all cases of illness, even if they 
occur after going home. 
I next subjected all the men to an examination intended to exclude 
all who were suffering from heart or lung disease, and those en- 
feebled by age or intemperance. All new men thereafter were re- 
quired to present a permit signed by me before they wrere allowed to 
enter the caisson. Though but few were actually rejected, the 
knowledge that they would be examined, doubtless deterred many 
who were not sound from applying for work. The personnel was 
therefore of the best, as it then appeared. Subsequent experience 
would, however, have modified my choice materially. 
On my recommendation a cup of good coffee was served to each 
man immediately upon leaving the caisson. It appeared to relieve, 
in a measure, the nervous prostration which marked the return to the 
open air; and possibly, by the effect which coffee is known to have, 
it may have done something, also, to check the tendency to too rapid 
tissue-change. 
A large room in the yard wTas fitted up with bunks and benches, 
which afforded the men an opportunity of resting wfiile the changes 
were going on in the system which were required to bring it into its 
normal condition after coming up. Connected with this room were 
conveniences for hot and cold bathing, and also lockers in which each 
man kept a change of dry under-clothing, to be put on immediately 16 
on coming up. Each man was supplied by the company with a pair 
of long rubber boots, which were rendered necessary by the work re- 
quiring them to stand more or less in the water. 
The physical conditions to which the men were subjected in their 
work were very peculiar. In the first place, in passing through the 
lock in going down, there was a very sudden rise of temperature from 
the condensation of the air This rise amounted to upwards of 30° 
F. in many cases, and not infrequently, when the outside tempera- 
ture was low, to 50° or 60°. This change in the temperature was 
coincident with an increase of atmospheric pressure of from 18 to 
36 lbs. to the square inch. At the same time the men passed from an 
atmosphere of the usual dryness to one saturated or super-saturated 
with moisture. The labor required in the caisson was not unusually 
severe. After from two to four hours passed in the compressed air, 
the men repaired to the locks, where in the space of from seven to 
fifteen minutes the pressure was reduced to the normal standard. 
As the result of the expansion of the air in the lock, the temperature 
fell as rapidly as it rose in the former case. This, which was felt to 
be a serious inconvenience in the Brooklyn caisson, was remedied on 
the New York side by surrounding the interior of the lock with coils 
of pipe heated by steam. The steam was shut off at all times except 
while locking out. 
The moisture of the atmosphere of the caisson, referred to above, 
was caused partly by the “water-packing” used in the condensers 
which supplied the air, and partly by the water with which the 
soil underneath the caisson was saturated. 
From the 25th of January, 1872, when I assumed medical charge 
of the men, until the 31st of May, when I resigned the position, 110 
cases of sickness occurred which were fairly due to the compressed 
air, and were of sufficient severity to come under treatment. Of 
these, three proved fatal. 
The sick were treated in the first instance at the yard, where 
a room was set apart as a temporary hospital. Cases occurring dur- 
ing my absence were treated by the engineer on duty, according to 
a specified plan; or, if the case was severe, I was summoned. 
Serious cases were ultimately sent to the public hospitals or to their 
homes. 
The ages of the men ranged from 18 to 50. They were of almost 
all nationalities, but I did not find that any sensible difference in 
ability to bear the work resulted from nativity, as observed by Pol, 
The habits of many of the men were doubtless not favorable to 
health, but everything which admonition could do, was done to 
restrain them from excesses. Many of them slept in crowded lodging- 
houses, where the beds or bunks were arranged in tiers, one above 17 
th e other ; in rooms in which there was scarcely an attempt at venti- 
lation. One of them fell a victim to spotted fever, contracted from 
such surroundings, and his death was at once ascribed by his com- 
rades to the effects of the condensed air. 
Serious inconvenience was occasioned to the men in the caisson by 
the large amount of unconsumed carbon from the gas, which floated 
in the air in the form of smoke. The inhalation of this produced 
more or less irritation of the air-passages, and gave rise to a very 
characteristic black expectoration. This continued for an astonish- 
ingly long period after the work in the caisson was terminated. At 
the time of my writing, nearly six months after the work was com- 
pleted, some of the men are still coughing up sputa, streaked with 
black. Where this carbon could have been lodged for so long a 
period, is a question which I am not prepared to answer. 
The smoking of the gas was found by some experiments of Mr. 
Collingwood, one of the engineers, to be due to the comparative 
immobility of the compressed air, which prevented the formation of 
the currents necessary to bring new supplies of oxygen to the flame. 
By reducing the aperture of the burners, and at the same time giving 
it such a form that the gas escaped in a thin sheet, a relatively great- 
er surface was secured for contact with the air. This obviated almost 
entirely the tendency to smoke, and added also to the illuminating 
power of the gas. 
The sinking of the caisson was begun on the 12th of December, 
1871, and the filling in with concrete was completed on the 20th of 
July, 1872 ; the duration of the submarine work being 221 days. 
During this period I was in the habit of frequently entering the 
caisson, remaining from one to two hours at a time. Yet in my case, 
with the exception of occasional slight pain in the maxillary sinuses, 
not the least inconvenience was experienced. 
CHAPTER THIRD. 
The effects of a highly condensed atmosphere upon the system 
may be divided into those which are physiological or consistent with 
health, and those which are pathological, and constitute or induce 
disease 
The physiological effects will be considered according to the organs 
or functions in which they are exhibited. 
Effect on the Hearing.—It is a law of acoustics that within the 
limits of mobility the denser the medium through which the sound 
waves are communicated, the larger the wave, and therefore the 
EFFECTS OF COMPRESSED AIK. 18 
louder the sound. This supposes, of course, that the ear itself re- 
mains under normal conditions. Such, however, is not the case 
when the observer is in a highly condensed atmosphere. The un- 
usual pressure upon all parts of the auditory apparatus opposes a 
mechanical obstacle to the freedom of vibration, which is essential 
to perfect hearing * Hence, although larger sound waves may strike 
upon the ear-drum, feebler impressions are communicated to the 
auditory nerve, and the sound appears to be fainter than in the open 
air. Thus, by repeated experiments, I found that a watch that could 
be heard distinctly at a distance of 18 inches in g very noisy place in 
the open air, could not be heard at a greater distance than two inches 
in the comparative silence of the caisson. 
At the same time the velocity of the waves of sound is greater, and 
hence the pitch is higher. A deep bass voice is changed to a shrill 
treble, and the prolonged, heavy sound of a blast is so modified as to 
resemble the sharp report of a pistol. 
This modification of sound is very striking, and is almost the only 
thing to remind the casual observer that he is moving about in an 
atmosphere three or four times as dense as that to which he is accus- 
tomed. 
A curious fact, noticeable under these circumstances, and one which 
was long ago observed in diving-bells, is that it is impossible to 
whistle. The utmost effort of the expiratory muscles is not suffi- 
cient to increase materially the density of the air in the cavity of the 
mouth, and hence on its escape there is not sufficient expansion to 
produce a musical note. A similar difficulty, though in a less degree, 
is experienced in speaking, and for this reason protracted conversa- 
tion is very fatiguing. 
Effect upon Respiration.—In a highly compressed air, the frequency 
of the respiration is increased. Dr. Jaminet gives the rate as 21 per 
minute, with a pressure of 33 lbs., which accords with my own ob- 
servations. He ascribes this increase of three or four per minute to 
an increased absorption of oxygen. Experiments show, however, 
that simply increasing the supply of oxygen, diminishes the frequency 
of respiration instead of increasing it. The true explanation, I 
think, is to be found in the fact that the quantity of carbonic acid 
held in solution by blood, as by water, is in proportion to the pressure 
to which the gas is subjected; and hence with the pressure existing 
in the caisson, the elimination of carbonic acid from the blood would 
not be as perfect as under normal circumstances, unless the air in the 
lungs were more frequently changed. As observed by Francois and 
Dr. Jaminet, the depth of the inspirations is also increased. With 
* An analogous fact was observed by Foley, viz., that his watch invariably loxt 
time when taken into the caisson, thus showing that the movements of the bal- 
ance-wheel were less free in the compressed than in the normal air. 19 
the view of appreciating the amount of increase of the respiratory 
movements, as well in amplitude as in frequency, I devised the fol- 
lowing plan : By a very simple contrivance attached to a steel band 
placed around the chest, a measuring tape was made to traverse with 
each inspiration a distance corresponding to the increase in the cir- 
cumference of the chest. The aggregate distance traversed in a given 
time was made the standard of comparison, and of course indicated 
the combined frequency and amplitude of the respirations. 
A number of trials with this instrument made upon myself in the 
open air, gave a very uniform result-of H inches of tape unwound 
every two minutes. On repeating the experiment in the caisson 
under a pressure of 33 lbs., 2f inches were unwound in the same 
time. 
Effect upon the Circulation.—It has been shown by numerous ob- 
servers that under a slightly increased pressure, such as is employed 
in compressed air-baths, the pulse loses in frequency from the first. 
This is doubtless due to an increased absorption of oxygen by the 
blood, which thus affords a sufficient supply to the tissues without 
the necessity of keeping up the usual activity of the circulation. In 
the course of some experiments undertaken nearly four years ago, I 
demonstrated that the same effect results under a normal pressure 
from adding oxygen to the air inhaled. But as the pressure in- 
creases, the question is transferred from the domain of chemistry to 
that of mechanics. The condensation of the tissues from the pres- 
sure to which they are subjected, and the consequent narrowing of 
the vessels, oppose a physical obstacle to the circulation, which is felt 
before the blood has time to become surcharged with oxygen, and 
while there is still a necessity for an active circulation. The labor 
of the heart is thus increased, and its action, in consequence, excited. 
I have frequently seen the pulse rise to 120 immediately upon enter- 
ing the caisson, where the pressure was from 30 to 35 lbs. to the inch. 
But after the lapse of a period varying in different cases from half 
an hour to two hours, the pulse falls back to its normal standard, or 
even, it may be, below it.* The blood has now become saturated 
with oxygen, and consequently a less active circulation is demanded. 
Doubtless, if the pressure were very gradually admitted, the pre- 
liminary rise in the pulse would not take place, the favorable chemi- 
cal action keeping in advance of and counteracting the unfavorable 
mechanical conditions. 
The effect of high atmospheric pressure upon the volume of the 
pulse is always, according to my observation, to diminish it. This is 
easily accounted for by the pressure exerted upon the artery, which 
prevents its yielding readily to the expanding force of each successive 
* My experience in this corresponds precisely with that of Dr. Jaminet. 20 
wave of blood. Hence the pulse is small, hard, and wiry. These 
characteristics are independent in a great degree of the frequency of 
the beat, although as the heart recovers from the irritable con- 
dition into which it is thrown by the sudden increase of the pressure, 
and settles down, so to speak, more calmly to its work, it contracts 
with more force, and the pulse gains somewhat in volume. These 
changes in both the frequency and fullness of the pulse are well shown 
in the annexed tracings, taken in the Brooklyn caisson. The upper 
line represents in each case the normal pulse, the lower line that in 
the compressed air. 
The difference in the readiness with which the process of adapta- 
tion to an increased pressure is accomplished in different persons is 
shown by the pulse-rate of eleven men taken an hour and a half after 
going into the caisson when the pressure was thirty-five pounds. The 
figures are arranged in the order of frequency. 
116—116—106—104—96—92—88—76—74—68—52. 
These figures give an average of ninety. On another occasion, with 
a pressure of thirty-two pounds, and a sojourn in the caisson of two 
and a half hours, the average was eighty. Whether a longer expo- 
sure to the same pressure would have produced a further decline in 
the frequency of the pulse is a question which the hours for working 
did not allow me to determine. 21 
It is remarkable* that the wide variations in the pulse-rate above 
mentioned were not accompanied by any symptoms appreciable to 
the individual. A man with a pulse of fifty-two, and another wfith 
one of one hundred and sixteen, felt equally well, and each wras en- 
tirely unconscious of anything unusual in the heart’s action. 
The effect of the pressure upon the cutaneous vessels is shoAvn by 
the pallor of the face, which is very marked, and continues for fif- 
teen or twenty minutes after leaving the caisson. The hands, too, 
feel shrunken, and the palmar surface of the fingers is often shriv- 
elled, as if soaked in water. The pressure acting upon all sides of the 
fingers empties them to a considerable extent of blood, rendering the 
skin apparently too large for them. The veins, too, on the back of 
the hand seem to be effaced. 
This absence of blood from the surface implies necessarily an ex- 
cess in the interior of the body, where the effect of the pressure is not 
as great. This point will come up again in considering the pathology 
of the Caisson Disease. 
Effect upon Temperature. —In none of the reports upon the effects 
of high pressure as employed for engineering purposes, have I been 
able to find any records of temperature. J. Lange,* however, found 
that under the comparatively slight pressure which is used as a reme- 
dy, the temperature of the body suffered a slight decrease. This is, 
no doubt, due to an increased absorption of oxygen, which has been 
shown by Mr. Savory and also by experiments of my own to produce 
this effect. 
During the work in the New York caisson when the pressure was 
about 32 lbs., I took the temperature of seven of the men an hour 
and a half after entering the caisson, and found that it averaged 
99.6° F., exactly one degree above the normal standard. At first I ac- 
cepted this as the result of the increased interstitial change so strong- 
ly insisted upon by Dr. Jaminet, but subsequent observation led me 
to interpret it differently. 
The temperature of the body in health is kept at about 98.6° F., by 
the constant evaporation from the surface. But in the caisson, as 
already mentioned, the air was always nearly or quite saturated with 
moisture, so that evaporation from the surface must have been prac- 
tically suspended. With the temperature of the air at 76°, as it w'as 
at the time of the observations, and the men engaged in severe labor, 
it is easy to see how the absence of the cooling process of evapora- 
tion from the surface would lead to a rise of one degree of the ther- 
mometer. This view is strengthened by the result of three observa- 
tions on a subsequent occasion, when the temperature in the caisson 
stood at 81°, instead of 76°. The average in this instance w7as 101°. 
* Vivenot. 22 
A rise of five degrees in the temperature of the air could not sensibly 
affect the rapidity of tissue-change, but if not counteracted by evap- 
oration from the skin, it would soon tell upon the temperature of the 
body. 
The influence of the liygrometric condition of the atmosphere 
upon the temperature of the body is a matter of daily observation. 
On a clear, dry day, with a high barometer, we are surprised to find 
the thermometer indicating a temperature much higher than our sen- 
sations would lead us to expect, while on the contrary, on a cloudy 
day, with a low barometer, we can scarcely persuade ourselves that 
the temperature is not many degrees higher than the thermometer in- 
dicates. In the dry, clear air of New Mexico I have supported a tem- 
perature of 110°, without inconvenience, while in the humid atmos- 
phere of the Florida Keys I have found it almost unbearable at 86°. 
Effect upon the Perspiratory Function.—Several writers have ob- 
served that it is immediately remarked by every one entering a 
caisson that the secretion from the skin is apparently immensely 
increased. It is noticeable even when the temperature of the air is 
moderate, but as this increases it becomes a very serious annoyance. 
The clothing quickly becomes saturated, which, besides the discom- 
fort it occasions, exposes to great danger of taking cold on going out 
into the open air. 
But a little examination served to show me that in the New York 
caisson, at least, there was really no increase of the secretion from the 
skin, but that, instead of evaporating, the moisture accumulated upon 
the surface, and thus simulated excessive SAveating. This Avas oAving 
to the moist condition of the atmosphere already mentioned, Avhich 
rendered the drying of the surface by evaporation impossible. The 
atmosphere possessed to an extreme degree the quality of “muggi- 
ness,” and the apparently profuse perspiration Avas merely an exag- 
geration of Avhat Ave suffer from in very damp weather, even though 
the temperature be not extreme. 
So far from the perspiratory glands being stimulated by the density 
of the atmosphere, it is probable that the anaemia of the skin already 
described, as resulting from the pressure upon the surface, would 
tend to lessen the secretion by diminishing the supply of blood to the 
glands. 
That there is not an undue amount of fluid carried off through the 
skin, is shoAvn by the absence of thirst so generally remarked. 
The foregoing explanation of the apparent increase of perspiration 
is important, as it bears upon the theory of excessive Avaste of tissue, 
in Avhich the perspiration is supposed to aid. 
Effect upon Digestion.—Nearly all authors who have written upon 
the effects of compressed air agree in stating that for a time, at least, 23 
it increases the appetite to a remarkable extent. Indeed this is one 
of the first and most favorable results observed where compressed air 
is applied remedially. With this experience my own observations in 
the main agree. It was frequently remarked by the men working in 
the New York caisson that their work made them unusually hungry, 
that they “ could not get enough to eat,” etc. Of course, it was not 
possible to obtain any exact data as to the relative amount of food 
consumed, but from careful inquiries I arrived at the conclusion that 
it was considerably in excess of what is usual in the case of men 
engaged in similar labor in the open air. Still, there were many 
exceptions to the general rule, especially among those who had been 
long engaged upon the work, and whose general tone was beginning 
to deteriorate. Among these, loss of appetite was often complained of. 
The fact of this generally increased appetite seems to point to an 
increased waste of tissue, to be supplied by a greater consumption of 
food. An increased absorption of oxygen such as we assume to take 
place, seems from the observations of several authorities* to imply 
greater activity of tissue-change as the ultimate result. But in this 
case I think it is scarcely safe to accept this explanation at once as 
conclusive and sufficient. It may well be questioned whether during 
the actual sojourn in the caisson the functions of digestion, absorp- 
tion, and assimilation proceed normally under the wide departure of 
the system from its natural conditions. If it could be shown that a 
considerable portion of the food taken before entering the caisson is 
but imperfectly digested or assimilated, the subsequent hunger would 
be readily accounted for. I am not aware that this point has ever 
been investigated, but I can scarcely believe that such an increase of 
appetite as is described could depend wholly upon increased inter- 
stitial change without giving rise to marked elevation of temperature 
and other symptoms denoting unusual chemical activity. On the 
contrary, I think it highly probable that an examination of the de- 
jecta would show them not to be entirely exhausted of nutritious 
material. At all events, until this point is subjected to rigid tests, it 
will be unsafe to regard the amount of food consumed as a measure 
of the metamorphosis of tissue. 
If the metamorphosis of tissue is really greatly accelerated through 
the influence of compressed air, it should be apparent in a more 
prompt healing of wounds. The following experiment was intended 
to test this point: 
Four pigeons were selected, as much alike as possible in size and 
vigor. Under the wing of each a wound was made by removing a 
circular piece of the integument about half an inch in diameter. 
Two of the pigeons were then sent down into the caisson, the other 
* “New York Medical Journal.” April, 1870. 24 
two being retained in the hospital on the wharf. The conditions in 
other respects were the same. At the end of six days the wounds in 
the two below were perfectly healed. Of the two above, in one the 
wound was perfectly healed, while in the other it was still covered 
by a scab, which fell off two or three days later. 
The result of this experiment would not indicate any considerable 
difference in the activity of the vital processes. I may remark that 
the workmen never spoke of the wounds or injuries they received as 
healing more rapidly than when working in the external air. 
Effect 'upon the Urinary Secretion.—Dr. Jaminet, in his observa- 
tions at St. Louis, found that the amount of fluid secreted by the 
kidneys was very much increased, in some instances nearly doubled, 
while the specific gravity was but little, if at all, below the usual 
average. This shows that the solid matter excreted was also in much 
greater quantity than usual.* But I cannot agree with him in attrib- 
uting this exclusively to the excessive waste of tissue from over-oxyd- 
ation of the blood. The explanation is to be found, I think, chiefly 
in the fact that the skin, as already stated, performs its function 
very imperfectly, owing to the impossibility of evaporation from the 
surface when the air is already loaded with moisture, and hence a 
portion of its duty is forced upon the kidneys, organs always ready 
to act vicariously for the skin or the mucous surfaces. 
Furthermore, the excretion of a large amount of urea indicates a 
relatively deficient oxydation of tissue, and is one of the characteris- 
tics of those diseases in which respiration is suddenly embarrassed, 
as, for instance, pneumonia. 
Another circumstance not to be lost sight of, is that the pressure 
upon the surface acts mechanically to congest all the abdominal vis- 
cera, and that congestion of the kidneys, within physiological limits, 
produces increased secretion of urine. 
From what precedes it will be inferred that I am not willing to ac- 
cept the view which practically sets no limit to the amount of oxygen 
that the system will appropriate in a sufficiently condensed atmos- 
phere. Even if absorbed by the blood, it does not follow that the 
excess of oxygen is received into the normal vital relations with the 
tissues. It may be held in simple compulsory solution in the blood, 
as in any other liquid ; it may even give rise to chemical changes in 
the blood, and solid tissues as in dead matter, and thus act as a poison, 
as asserted by M. Bert.t but we have no warrant for believing that it 
so acts as to cause the removal of particles not 3ret effete, and which 
but for this would have remained normal active constituents of the 
* These observations accord with those of Foley, J. Lange, Pol, Pravaz, and 
others. 
t L’lnstitut, July 3, 1872 25 
body. Behind mere chemical action lies a vital principle in accord- 
ance with which each molecule is born, as it were, into the economy, 
reaches maturity, performs its function, becomes effete, and is suc- 
ceeded by a new molecule; and to break in upon this order is to 
strike at the very essence of life. 
I do not intend by this to deny that an atmosphere highly oxygen- 
ated, either by the addition of oxygen or by compression, is capable 
of accelerating the vital processes within certain limits. I only 
contend that these limits correspond with the extreme limit of 
physiological demand—that the capacity of the system to appropriate 
and use oxygen has a definite relation to the possible wants of the 
system under natural conditions. For a contingency beyond these, 
nature has made no provision. 
CHAPTER FOURTH. 
PATHOLOGICAL EFFECTS. 
The pathological effects of high atmospheric pressure comprise 
certain phenomena easily explained upon mechanical principles, and 
in addition to these, a group of symptoms, having a definite relation 
to each other, and constituting a specific affection, which, from the 
peculiarity of its origin, I propose to call the Caisson Disease. 
The affections, which are of a purely mechanical nature, relate to 
the cavities communicating with the nasal passages, such as the ears 
and the frontal and maxillary sinuses, etc. 
Affections of the ears are mentioned by nearly every writer on the 
subject of compressed air, and are extremely common. They 
depend, for the most part, upon closure of the Eustachian tubes, by 
which communication of the cavity of the middle ear with the 
external air is cut off. The men under my charge were warned most 
strenuously not to go into the lock unless they were able, when 
holding the nose and blowing forcibly, to feel the air enter both 
ears, thus insuring that the tubes were pervious. Nevertheless, cases 
often occurred in which this precaution was neglected, and the indi- 
vidual was, as a consequence, “caught in the lock,” unable to 
“ change his ears.” This inability to equalize the pressure upon the 
two sides of the ear-drum, caused extreme pain, and sometimes 
entailed serious results. The effect is two-fold. The pressure upon 
the outside of the drum being greater than upon the inside, the mem- 
brane is pressed inward with a force, which, if it does not produce a 
rupture, at least causes a degree of tension which so delicate an 
organ as the ear is not fitted to bear with impunity, and which may 
be the starting point of an acute inflammation. (See Case I., p. 43.) 26 
But the pressure may be so great as to rupture the drum at once, as 
in Case II., p. 43. 
When there is continued exposure to the effect of compressed air, 
with closure of the Eustachian tube, the structures within the cavity 
of the tympanum not being acted upon by the increased pressure, are 
placed relatively in the same position as the skin under a cupping- 
glass, and the same result follows, viz., intense congestion, which 
may, in this case, lead to inflammation. Indeed, the difference 
in pressure within and without is much greater than in the case 
of the cupping-glass, since in the latter it cannot exceed one at- 
mosphere, while in the former it may be two or three atmospheres. 
The stoppage of the Eustachian tube may very frequently be over- 
come by forcing in air through the nose after the method described 
by Politzer. In this way a great many of the men under my care 
were enabled to continue their work, who otherwise could not have 
done so, without incurring serious risk. This simple operation was 
constantly called into requisition, as many as four or five of the men 
sometimes presenting themselves in the course of my visit to have 
their “ ears blown out,” and it rarely happened that they experienced 
any difficulty afterward on entering the lock.* 
Three cases of extreme deafness came under my notice, two of 
them in laborers, and one in the person of a gentleman, who was ad- 
vised by a physician to visit the caisson with the hope that he might 
benefit from the action of the compressed air. In all these 
cases the hearing was very much improved while in the caisson, hut 
on returning to the open air the former degree of deafness immedi- 
ately returned. 
A number of cases of otities are mentioned by Francis, as occur- 
ring under his observation during the sinking of the caissons at Stras- 
burg.f His favorite remedy was oil of jasmine dropped into the 
ear. He also employed leeches and fomentations. He condemns 
catheterism of the tubes, on theoretical grounds, while admitting 
that he had never employed it. 
Pain, more or less severe, in the frontal or maxillary sinuses was 
sometimes experienced. This was doubtless caused by a temporary 
closure of the passage leading to the nasal cavity. In one case, in 
which the frontal sinus was affected, the pain, though not severe, 
was very persistent, continuing for several days. 
In one case pain in the frontal sinus was felt as the pressure was 
increasing in the lock, and again, and more severely, as the pressure 
was reduced in returning to the open air. This latter pain was ac- 
companied by a discharge of bloody mucous from the nose. In this 
case there was doubtless closure of the passage into the sinus, thus 
* I am under obligations to Dr. lloosa for valuable hints in reference to the treat- 
ment of these cases, 
t See page 9. 27 
preventing the equalization of the pressure, and giving rise to the 
pain first felt. There resulted also congestion of the lining mem- 
brane, followed by an increased flow of mucous and extravasation of 
blood. But in the course of the two hours passed in the caisson, the 
air gradually filtered through the obstruction, and when the outside 
pressure was removed, the air thus imprisoned forced a way out, car- 
rying before it the mucous and blood that had accumulated in the 
sinus. (See Case IV., p. 43.) 
It becomes an interesting question what degree of condensation of 
this atmosphere will prove directly fatal. Dr. Richardson, of Lon- 
don, told me recently that he had experimented largely upon this 
subject, and that for the small animals which he had employed, such 
as rabbits, cats, dogs, etc., the limit of endurance seemed to be be- 
tween six and seven atmospheres. He found, however, that the re- 
sult varied widely, with comparatively slight variations of tempera- 
ture, such as would have no appreciable effect upon vitality under 
other conditions. 
CHAPTER FIFTH. 
THE CAISSON DISEASE. 
Definition.—A disease depending upon increased atmospheric pres- 
sure, hut always developed after the pressure is removed. It is charac- 
terized by extreme pain in one or more of the extremities, and sometimes 
in the trunk, and which may or may not be associated with epigastric 
pain and vomiting. In some cases the pain is accompanied by paralysis 
more or less complete, which may be general or local, but is most fre- 
quently confined to the lower half of the body. Cerebral symptoms, 
such as headache and vertigo, are sometimes present. The above symp- 
toms are connected, at least in the fatal cases, with congestion of the 
brain and spinal cord, often resulting in serous or sanguineous effusion, 
and ivith congestion of most of the abdominal viscera. 
SYMPTOMS. 
Neuralgic Pains.— These constitute in general the first and most 
characteristic symptoms, and are very seldom absent. The accession 
is often very abrupt, as if the patient “had been struck by a 
bullet.” At other times the pain is slight at first, but rapidly increases 
in intensity. In well-marked cases the suffering is extreme, men of 
the strongest nerve being completely subdued by it. It is “ as if the 
flesh were being torn from the bones.” The pain is usually of a 
remittent or paroxysmal character, the exacerbations occurring at 
short intervals, especially if the patient attempt to move. Though 
usually designated as “cramps,” these pains are rarely accompanied 
by muscular spasms. They generally begin in one or both of the 28 
knees, shifting to the legs or thighs, and then perhaps creeping up 
along the trunk to seize upon the shoulders and arms. Not unfre- 
quently the severest pain is felt in the spine, and especially in the 
lumbar portion. There is usually some degree of tenderness with the 
pain, so that the patient will complain if friction be applied too 
vigorously. There is also a painful stiffness in the affected limbs, 
that precludes motion in the absence of actual paralysis. 
In some cases, there are swelling and heat fts well as tenderness, 
indicating engorgement of the tissues, and this may persist for seve- 
ral days, being followed occasionally by discoloration, as if from a 
bruise. (Case VII., p. 44.) 
Francois mentions a case in which the engorgement was followed 
by suppuration. In two of my cases, minute spots of extravasated 
blood in the substance of the skin at the seat of pain, gave the sur- 
face the appearance of being spattered with red ink. (Case NI., 
p. 45.) 
A curious case of the swelling of the mammary gland recurring 
each day is given among the Illustrative Cases, No. IX. Frangois 
relates a similar instance. 
The Pulse.—At the outset of the attack the pulse will differ 
according to the time which has elapsed since leaving the caisson, 
being, as a rule, quicker and more frequent in proportion as the time 
is shorter. Dr. Jaminet observed that if the attack occurred imme- 
diately after coming up, the pulse usually ranged from 95 to 115, 
while, if it were delayed for half an hour, the pulse would be 
slowr—perhaps as low as 60. 
But as these rates do not differ from those in healthy persons at 
the same periods after leaving the caisson, they do not possess any 
special significance in those taken sick. 
The subsequent character of the pulse is simply indicative of the 
general condition of the patient. 
The Skin is usually cool at first, often of a slightly leaden hue, and 
nearly always covered with a profuse cold perspiration, standing out 
in beads upon the surface. This perspiration is very characteristic. 
At first I supposed it to be owing to the excessive pain which the pa- 
tient w'as suffering; but subsequently it occurred in several cases in 
which the pain was slight or entirely absent. (See Case VI.) I w'as, 
therefore, inclined to attribute it to a relaxation of the cutaneous 
capillaries through some nervous agency analagous in its action to 
what we see in cases of extreme terror, and having its origin in the 
general disturbance of the nervous system which characterizes the 
disease. 
In several instances in which I ascertained the temperature in the 
axilla, it wras found to be normal. 29 
Epigastric Pain and Vomiting.—Pain at the pit of the stomach, 
usually, but not always, attended by vomiting, is of frequent occur- 
rence. It occurred in 24 per cent, of my cases. This is a much 
smaller percentage than that observed by Dr. Jaminet, who found 
the gastric symptoms to be present in 66 out of 77 cases. This may 
be owing to the pressure being greater at St. Louis than at New York, 
nearly all of Dr. Jaminet’s cases occurring under a pressure of 40 
lbs. and upward, while the pressure at New York did not rise above 
36 lbs. 
The pain in the epigastrium, if not relieved by treatment, is gener- 
ally followed within a brief period by vomiting, which may continue 
with great persistence even after the pain has ceased. In most cases, 
however, the vomiting is limited to the ejection of the contents of 
the stomach. 
In a few instances I observed the occurrence of vomiting without 
the usual preceding pain. In these cases there was also dizziness, in- 
dicating that the vomiting was of cerebral origin. 
Paralysis —This occurred to a greater or less degree in 47 out of 
77 cases observed by Dr. Jaminet. This is at the rate of 61 per cent. 
At New York it occurred in only about 15 per cent, of the cases; 
the difference being due, no doubt, to the difference of pressure. 
The paralysis affects most frequently the lower half of the body, 
but it may include the trunk or one or both arms. In rare instances 
the arms alone are affected. The paralysis usually comes on a short 
time after the beginning of the pains, but it may occur where there 
is very little if any pain. (Case XXY.) It affects sensation as well 
as motion. The patient does not, however, obtain relief from his 
suffering, since the pain in the limbs will continue after pain from 
other sources is no longer felt. Thus a leg, for example, may be en- 
tirely insensible to pricking or pinching, while at the same time it is 
the seat of extreme suffering. In fact, the neuralgic pain and the 
paralysis seem to be so far independent of each other, that either 
may exist separately as well as both together. 
The degree of paralysis may vary from mere weakness of the 
limbs, with slightly impaired sensation, including a loss of “hold 
upon the ground ” in walking, to complete loss of motion and sensa- 
tion in the affected part. Even the minor degrees generally involve 
the bladder, and in two or three of my cases the paralysis, after the 
first day or two, was confined to this organ. 
Cerebral Symptoms.—Symptoms of a transient character are often 
observed, which have their origin in the brain. They consist of 
headache, dizziness, double vision, incoherence of speech, and some- 
times the last from syncope. They are usually of 
very short duration, passing off in a few hours. In the fatal cases, 30 
however, a condition of profound coma is the usual forerunner of 
death. The occurrence of this symptom leaves but little hope of the 
patient’s recovery. 
Prognosis.—The duration of the Caisson Disease varies from three 
or four hours to six or eight days. When paralysis takes place, this 
may continue for weeks, or it may pass off within twelve hours. 
The cases marked only by neuralgic pains do not generally last more 
than twelve hours, though some continue five or six days. 
Death occurs only in cases which are severe from the first, and are 
marked by symptoms of serous or sanguineous effusion about the 
brain or cord. 
Morbid Anatomy.—The constant lesion in fatal cases of Caisson 
Disease is congestion of the brain or spinal cord. This congestion 
may be evenly distributed, or it may vary in intensity in different 
localities. This is especially true as regards the cord. The conges- 
tion affects both the meninges and the substance of the brain or 
cord. In some instances extravasation of blood takes place, as in 
Case XXVI., chapter 6. In most of'the published cases there was 
found also more or less serous effusion in the arachnoid. 
The tissues of the scalp and those surrounding the spinal column 
are sometimes engorged. Dr. Jaminet describes a case in which the 
tissues over tire spine were congested, the vascularity increasing 
regularly as the dissection proceeded deeper toward the vertebral 
column. 
When sufficient time elapses before death, there may be softening 
of the brain, occurring in spots. This is probably due to occlusion 
of the vessels by coagula formed during the primary congestion. 
Congestions also occur in other localities, and especially in the 
solid abdominal viscera. The liver and spleen have been found 
engorged in nearly every case. The kidneys, too, are usually con- 
gested, and in several cases described by Dr. Jaminet, clots of blood 
were found' extravasated in the organ. 
The mucous membrane of the stomach, intestines, and bladder is 
often found injected and marked with eccliymotic patches. 
The lungs, in cases of true Caisson Disease, seldom present any 
other change than simple hypostatic congestion. 
Pathology.—It is probable that the pathology of this disease is not 
entirely uniform in all cases. Doubtless, the chief element in it is 
the congestions already described, and especially of the brain and 
spinal cord. The mechanism, therefore, of these congestions, be 
comes a subject of paramount importance. 
It is obvious that if the blood were exposed to an equal pressure in 
all parts of the body, there would be no change in its distribution. 
11 Physical Effects of Compressed Air. P. 20. 31 
It is equally clear tliat the blood, if free to move, will pass from a 
place where the pressure is greater to one where it is less. The 
body is made up of structures of different densities, and presenting a 
varying resistance to compression. But permeating these structures 
in every direction are vessels in perfect communication throughout 
the entire system, and filled with a mobile fluid, which is free to 
change its locality in obedience to any force which is brought to act 
upon it. Now, when the surface of the body is subjected to an 
even pressure on all sides, the tendency is to a distribution of this 
pressure toward the centre. If the body were composed entirely of 
solids, this could be effected only by the compression of those solids, 
and a point would very soon be reached where the resistance would 
balance the compressing force, and the parts lying more toward the 
centre would remain unaffected. But the presence of a fluid in the 
structures, with free channels in which to move, changes all this. 
While the solid tissue resists compression, the fluid blood retreats 
from the surface to the centre, and accumulates there until an equi- 
librium of pressure is produced. 
Hence we deduce the law, that under high atmospheric pressure 
the centres will be congested at the expense of the periphery. 
But, aside from location, vessels coursing through dense and resist- 
ing organs, will be less exposed to external pressure than those pass- 
ing through soft and yielding structures. Hence a second law, that 
firm and compact structures will he congested at the expense of those 
more compressible. 
But there are structures very soft and yielding in themselves, yet 
enveloped in a rigid casing of bone which entirely shuts off the influ- 
ence of external pressure- Hence the establishment of the equilib- 
rium in them is wholly dependent upon an afflux of blood. This 
gives us the third law, that structures within closed bony cavities 
are congested at the expense of all others. 
In accordance with these laws, we shall find that while in the cais- 
son, the condition of the different parts in regard to the supply of 
blood will be as follows : 
The skin and the superficial structures will be anaemic.* The cen- 
tral portion of the limbs and the interior organs of the body will be 
congested. The solid viscera of the abdomen will be especially en- 
gorged on account of both situation and structure. The brain and 
spinal cord, and the interior of the shaft of the long bones, will be 
congested to a high degree from the operation of the third law. 
These changes are not perfected until a considerable time has been 
passed in the compressed air. The circulation up to this point goes 
on everywhere with vigor, the change being in the relative calibre of 
* This is shown by the pallor which is very characteristic. See p. 21. 32 
the vessels, not in their tension. The counter-pressure becomes uni- 
form throughout the whole vascular system, but this counter-pres- 
sure supersedes the natural muscular resistance or tone of the vessels, 
which have become passive tubes. The blood is distributed not in 
accordance with the physiological demands of the different parts, but 
in obedience to overpowering physical force. 
This is the condition of the circulation at the moment that the pro- 
cess of locking out begins. Yet the changes which have taken place 
up to this point are not the cause of the morbid phenomena which 
constitute the Caisson Disease, else the attack would take place while 
in the compressed air, instead of after leaving it. It is evident that 
the removal of the pressure, and not the pressure itself, is the immedi- 
ate cause of the seizure. 
This removal is effected in the few minutes which are occupied in 
locking out. But it is not to be supposed that the vessels will in- 
stantly assume their normal condition. They are in a state of relax- 
ation, not only in the congested, but also in the anaemic parts; in the 
former, because of over-distension—in the latter, because the mustu- 
lar coat cannot at once recover from its inaction. The aggregate 
capacity of the vascular system will, therefore, be in excess, com- 
pared to the volume of blood to be conveyed; or, in other words, there 
will be a lowering of vascular tension. 
Hence, the circulation will be languid, and the congested parts will 
not readily empty themselves of the excess of blood which they con- 
tain. Especially will this be the case in the brain and spinal cord, 
where the conditions are most favorable for the production of con- 
gestion. The capillaries being clogged with effete blood, the nutri- 
tion of the part must suffer, and disturbance of function will result. 
It is to this, I think, that the delirium, and the transient loss of 
consciousness, which occasionally occur, are to be attributed. When 
the spinal cord is the seat of this condition, pain in the parts deriving 
their nerves from that section of the cord may result, or paralysis 
more or less complete may follow. 
This appears to me to account for the phenomena in those cases in 
which the local symptom is paralysis or pain of a transient or shifting 
character. These cases may, I think, be considered as entirely spinal 
in their origin. But in many cases there are evident local changes 
such as tumefaction, rise of temperature, etc., which indicate local 
irritation, and wdiich are probably due to obstruction of the vessels 
of the part as a sequel to the local congestion. This explanation is 
applicable also to those cases in which the pain is fixed in one locality, 
which may be very much circumscribed, and where it persists for 
days without intermission, feeling, as the patient expresses it, “ as if 
it were in the bone,” where it very likely is. Such a pain presents a 33 
marked contrast to those shifting pains which have been described, 
and if considered of spinal origin, would indicate a serious lesion con- 
fined to a minute portion of the cord. That such a circumscribed 
lesion might occur as a very rare exception, must be admitted ; but 
that it should be present in a considerable proportion of cases is in 
the last degree improbable. 
The testimony of all observers is, that the liability to attack is di- 
rectly as the duration of the stay in the caisson. This admits of an 
easy explanation on the theory which I have advanced. The more 
thoroughly the system has become adapted to the change in the 
circulation, the less readily it will resume its normal condition when 
the pressure is removed. The congested vessels, especially, will lose 
their contractility in proportion to the time their muscular fibres have 
been upon the stretch. 
It wras suggested by Francois, that the morbid phenomena result- 
ing from high pressures might be due to the liberation of air which 
had been absorbed by the blood while under pressure, but which was 
set free again when the pressure was removed. 
The same idea has since been advanced by Prof. Rameaux, of 
Strasburg. 
Within the past year M. Paul Bert has communicated to the 
French Academy* the results of a series of experiments made upon 
animals with very high pressures, reaching sometimes to 19 at- 
mospheres. He shows that when death is the direct result of the pres- 
sure it is induced by an excessive absorption of oxygen, which then 
enters into chemical union with the blood, and acts as a poison. He 
found that the gas which escapes from the blood after the pressure is 
removed, is composed of a mixture of nitrogen and carbonic acid, 
with scarcely a trace of oxygen, the oxygen being retained by the 
blood. This poisoning by oxygen, however, produces its effect while 
in the compressed air, and therefore cannot be a factor in the pro- 
duction of the Caisson Disease. 
But M. Bert re-asserts the theory of Francois and Prof. Rameaux, 
vrith this difference : that he claims that bubbles of nitrogen instead of 
air are the cause of the interruption of the circulation. These bub- 
bles he has discovered after death in the vessels of the brain and 
cord. But he states that when the pressure does not exceed five 
atmospheres, three minutes allowed for the restoration of the nor- 
mal pressure will be found to prevent the formation of these 
globules of nitrogen. Now, we find the Caisson Disease occurring 
when the pressure does not exceed two atmospheres, and when six 
to eight minutes are allowed for locking out. It would seem that 
under these conditions, the gas should escape through the lungs as 
* Comptes Kendua, August, 18T2, and February and March, 1873. 34 
rapidly as it is disengaged from tlie blood. Moreover, we find that 
in the Caisson Disease the attack often comes on several minutes or 
even hours after leaving the compressed air. During this interval, if 
any free nitrogen were circulating with the blood, it should constant- 
ly become less by diffusion through the pulmonary membrane, and it 
is scarcely conceivable that if the quantity at the moment of emerg- 
ing into the open air were not enough to produce obstruction of the 
circulation, such an effect could take place at a later period. 
It is also very difficult to reconcile with M. Bert’s theory the fact 
of the comparative immunity from danger which results from re- 
peated exposures to the effects of compressed air. If the action be 
that of purely" physical causes, habit could make no difference. The 
obstruction of the vessels described by Bert is a condition of which 
the system could never become tolerant by frequency of repetition. 
Ou the other hand, it is perfectly conceivable that vessels which are 
required to receive a varying quantity of blood at different times 
may acquire the power of more ready" adaptation to these changes of 
quantity, since this is only an extension of the physiological prin- 
ciple which we see exemplified in all organs which have an intermit- 
tent function. Hence this objection, which lies against the explana- 
tion of M. Bert, does not apply to the views as to the pathology of 
the disease which I have advanced. 
Thus, while recognizing the value of M. Bert’s observations, I am 
still of the opinion that he is in error in applying them to the com- 
paratively low pressures and gradual decompression which are con- 
sistent with the production of the Caisson Disease. 
In order further to test this question, I performed the following 
experiment: The pressure in the caisson being about 35 lbs. to the 
square inch, a dog was sent down, and allowed to remain seven hours 
in the compressed air. At the end of that time I went down, and 
after killing the animal with prussic acid, I opened the vessels of the 
neck, and allowed four ounces of blood to flow into a six ounce vial. 
The space above the blood was then completely filled with olive oil, 
and a cork, pierced by one leg of a small U-shaped tube, was forced 
tightly into the bottle, displacing a portion of oil, which escaped 
through the tube. By this arrangement every particle of air was 
excluded from the apparatus, even the tube, which extended a little 
below the cork, being entirely" filled with oil. The object of the oil 
was to avoid the difficulty which would arise from coagulation of the 
blood in the tube if blood only" were employed. 
The apparatus thus arranged was then taken into the open air. 
While passing through the lock five minims of oil escaped from the 
tube, which amount was increased during the next half hour to eight 
minims. The temperature of the caisson and that of the external 35 
air were almost exactly alike, so that the result obtained could not be 
influenced by contraction or expansion due to temperature. The 
eight minims, therefore, represented the bulk of air which was disen- 
gaged from the blood in consequence of the removal of the excess of 
pressure. This is only of the bulk of the blood experimented 
upon. Now the experiments of Demarquay* show that from 80 to 
150 c. centimetres of oxygen can be thrown into the veins of a me- 
dium-sized dog in the space of four or five minutes, without pro- 
ducing serious consequences ; and other observers have demonstrated 
that air slowly introduced into the veins escapes through the lungs, 
and that a large quantity can be injected in this way without danger. 
Hence with the small amount of air which my experiment shows 
to be disengaged from the blood, and with the process extended over 
eight or ten minutes at least, it seems clear that we cannot explain in 
this way the phenomena observed in the Caisson Disease. 
Causes.—The one essential cause, without which the disease can 
never be developed, is the transition to the normal atmospheric pres- 
sure, after a prolonged sojourn in a highly condensed atmosphere. Hence 
we have to consider two elements, pressure and time. As the mo- 
mentum of a moving body is found by multiplying the weight by the 
velocity, so the danger in these cases is as the degree of pressure to 
which the person has been exposed, multiplied by the duration of the 
exposure. 
But inasmuch as a prolonged sojourn in the caisson does not in 
every case produce the disease (many of the men employed escaping 
it entirely), it follows that there must be concurrent causes which de- 
termine its development. This is what we observe in many other 
diseases of a specific origin. Thus the essential cause of intermit- 
tent fever is exposure to a peculiar malaria, yet only a portion of 
those so exposed are affected by the disease. 
The first of the concurrent causes of the Caisson Disease is a 
special predisposition. This is occasionally strongly marked, some 
persons being affected by a short exposure to a low pressure from 
which there would generally be experienced no inconvenience what- 
ever. 
The study of these cases has led me to the suspicion that they 
afford a key to the singular, though very common, predisposition to 
pains in the limbs on the approach of a storm. These pains are gen- 
erally considered to be of a rheumatic character, and to depend upon 
the dampness of the atmosphere. But inasmuch as the disease we 
are considering affords examples of pains precisely the same in char- 
acter, but immensely intensified in degree, resulting from the diminu- 
tion of an atmospheric pressure to which the system had adapted it- 
* Pneuraatologie Medicate. P. 664. 36 
self, and irrespective of any question of humidity, analogy suggests 
that the so-called rheumatic cases are simply exaggerations of a pre- 
disposition, identical in kind with the one under discussion, and are 
produced by the low barometric condition of the atmosphere which 
precedes a storm, and not by the influence of moisture. It is true 
that the change in the pressure is insignificant when compared with 
that which produces the Caisson Disease, but it is supplemented by the 
immensely greater duration of the higher pressure to which the sub- 
ject has been previously exposed. Persons suffering in the manner 
referred to, regard themselves as walking hygrometers, and are ac- 
customed to say, ‘ ‘ I feel the dampness in my bones. ” I would sug- 
gest that they are rather barometers, perhaps quite as sensitive as 
the instrument of Torricelli. 
Perhaps the most frequent exciting cause of the Caisson Disease is 
too rapid locking out. Indeed, it is altogether probable that if suffi- 
cient time were allowed for passing through the lock, the disease 
would never occur. But what is sufficient time for one is too short a 
time for another, and as no work could be accomplished if the time 
in the lock were indefinitely prolonged, all that can be done is to fix 
upon a duration for the process of locking out which shall be propor- 
tioned to the pressure, and as great as is consistent with the circum- 
stances, and then to see that the rule is rigidly observed. The natu- 
ral impatience of the men to reach their homes, makes the delay in 
the lock irksome, and great firmness is required on the part of the 
lock-tender to prevent the escape-cocks being opened more widely 
than is consistent with safety. In locking out, at least five minutes 
should always be allowed for each additional atmosphere of pressure. 
Newness to the Work.—Unquestionably the liability to the Caisson 
Disease is greatest in those exposed for the first time to the influence 
of the compressed air. New hands are very apt indeed to suffer more 
or less during the first week, and a number of the severest cases that 
came to my notice, occurred in men who had worked but a single 
watch, though first attacks were much more likely to occur after the 
second watch of the first day. Those least affected were such as 
began work when the pressure was comparatively slight, and contin- 
ued without intermission as the pressure increased. It seemed that 
the system after a time became adapted to the changed conditions, 
and was protected, in a measure, from their effects. Nevertheless, 
some serious cases occurred among the old hands, especially when for 
any reason their stay in the caisson was prolonged beyond the usual 
time, thus showing that their immunity was merely relative. A 
sudden increase of pressure, also, even though very slight, was cer- 
tain to develop new cases—men thoroughly inured to the work 
often being affected under such circumstances. 37 
Fullness of Habit.—After the work in the New York caisson had 
been some months in progress it was observed that there was a pre- 
ponderance of stout, heavily-built men among those taken sick. 
This led me to examine my records carefully in reference to this 
point. I found that up to May 22, they embraced 86 cases of well- 
marked Caisson Disease. These I divided into three classes, accord- 
ing to the build of the individual. Those who were tall in propor- 
tion to their weight, and rather lean in flesh, were classed as spare ; 
those who were thick-set and muscular, without being fat, were set 
down as medium ; and those with prominent abdomen, full cheeks, 
and general tendency to obesity, were styled heavy. The 86 cases of 
illness were found to be distributed among these three classes as fol- 
lows : Spare, 28 ; medium, 22 ; heavy, 36. 
Considering that among laborers below the age of 45 (and none of 
the cases were above that age), the class described as heavy are very 
much in the minority, these figures were sufficiently striking. 
In order to arrive at the converse of this I desired the time-clerk 
to prepare a list of those who had lost least time from illness, i.e., 
those least affected by the work. The figures in this case were even 
more striking. The list comprised the names of 42 men, who were 
classified as follows : Spare, 25; medium, 14; heavy, 3. 
I next separated the severer cases of illness, which Avere marked 
by paralysis; of these there were 13: Spare, 2 ; medium, 3 ; heavy, 
8. Those who had died up that time, three in number, were all heavy 
men. 
These results may be tabulated as follows: 
Spare. 
Medium. 
Heavy. 
Total. 
Lost little or no time from sickness... 
25 
14 
3 
42 
Taken sick 
28 
22 
36 
86 
Paralyzed 
2 
3 
8 
13 
Died 
" 
3 
3 
These figures show unmistakably that a tendency to fullness of 
habit renders work in a compressed atmosphere much more hazard- 
ous. Persons of this build have more fluids in the body, the distribu- 
tion of which is changed by the pressure, in the manner before 
stated, and it is therefore not surprising that the effect upon them 
should be greater than upon lean and sinewy persons, whose bodies 
contain a minimum of fluid. 
Severe Exertion Immediately after Leaving the Caisson.—As at the 
moment of going out of the compressed air the system undergoes a 38 
violent reaction, it is manifestly unfitted to bear in addition a severe 
tax upon tlie muscular strength. Hence, the ascent of a long flight 
of stairs, immediately after leaving the air-lock, is as wrong in theory 
as it has proved bad in practice Dr. Jaminet has described most 
graphically the ill effects arising from this cause at St. Louis, and 
the relief experienced when the men were saved the necessity of 
climbing the steps by the substitution of a steam elevator.* Con- 
trast this with the experience of M. Triger, whose apparatus at Cha- 
lonnes w'as so arranged that the ascent of the ladder took place in 
the compressed air, the lock being placed at the top instead of the 
bottom of the shaft. lie found that the men ascended a distance of 
70 feet without becoming in the least out of breath; making the 
ascent, in fact, much more easily than if it had been in the open air. 
I hoped at one time that an opportunity would be afforded at the 
New York caisson for obtaining some data bearing upon this point. 
During the early part of May an elevator was arranged, but unfortu- 
nately just at that period great changes took place in the force, and 
at the same time various interruptions in the work occurred, so that 
the matter was hopelessly complicated, and no data for comparison 
could be obtained. 
The Abuse of A Icohol. —Several writers have remarked that habit- 
ual drinkers are more likely to be affected by compressed air than 
those who used spirits moderately or not at all. It is stated by the 
director of the work at Doucliyt that the attacks from which the 
men suffered were ‘ ‘ almost always coincident with some excess com- 
mitted in the interval of the shifts. ” It is easy to perceive that as 
the disease is characterized by cerebral congestion, the abuse of alco- 
hol, which has a tendency to produce the same result, would act as a 
predisposing cause. Although no cases directly attributable to this 
cause'came under my observation, I have no doubt that there is 
danger from it; and I therefore rejected several men who applied for 
work in the caisson, for no other reason than that their appearance 
indicated an habitual excessive use of alcohol. 
Entering the Caisson Fasting.—Dr. Jaminet insists very strongly 
upon the influence of this cause, and cites instances to prove his 
position. Several cases corroborative of his views occurred under 
my observation. One of the rules for tlie men working in the New 
York caisson, prohibited entering the compressed air without having 
taken food, and in addition to this each new hand was especially 
cautioned as to the danger of disregarding this precaution, and the 
foremen were directed to use every effort to secure its observance. 
Yet notwithstanding all this a number of very severe attacks were 
* See Dr. J.’s Report, p. 120. 
t Annales d’Hyg. Pub. et de Med. Legale, 1864. 39 
found to bo coincident with, if not dependent upon, violations of this 
rule. In these cases epigastric pain and retching were prominent 
symptoms. (See Case XXI., p. 47.) 
Treatment.—The treatment of this disease will depend upon the 
severity of the case, and the presence or absence of gastric symp- 
toms or of paralysis If we have to deal with the neuralgic pains 
only, the chief reliance must be upon anodynes, administered with a 
liberal hand. Fortunately the pain, though very severe while it 
lasts, is in most cases of short duration, the attack passing off 
usually in a few hours. 
It is, therefore, quite practicable to keep the patient under the 
influence of morphine during the whole time, and thus enable him to 
escape entirely all extreme suffering. But large doses will be 
required, the intense pain inducing a remarkable tolerance of the 
drug. It was my habit to give half a grain of morphine at the 
outset, and a quarter of a grain every half hour afterward until 
relief was obtained. When employed hypodermically, which is the 
method affording most prompt relief, somewhat smaller doses may 
be used. 
In some instances I have obtained the very best results from hypo- 
dermic injections of atropine at the seat of pain ; but in other cases 
it failed to procure relief, and, upon the whole, I consider it inferior 
to morphine. 
Dr. Jaminet, regarding the affection as wholly the result of 
exhaustion, relies entirely upon stimulants and concentrated nourish- 
ment, ignoring the aid of anodynes altogether. I can see no reason 
for this, even admitting to the fullest extent his theory of the dis- 
ease, for nothing can be more exhausting than the intolerable pain 
which characterizes this affection, and nothing could act more 
promptly as a restorative than an efficient anodyne. 
Starting from the theory already given as to the mode in which 
the disease is produced (a theory which was constructed wholly upon 
the observations of others), I was led to the idea that benefit would 
be derived from the use of an agent that would induce contraction of 
the capillaries, and thus correct the want of tone which I considered 
to lie at the foundation of the difficulty. For this purpose I pro- 
posed the use of ergot before I had ever seen a case of the dis- 
ease. I reasoned that it would be useful, first, by contracting the ves- 
sels of the brain and spinal cord, and relieving their congested state ; 
and secondly, by restoring tone to the superficial vessels, and thus 
imparting vigor to the circulation. 
An extended trial warrants me in saying that the results have jus- 
tified the theory. In my hands, though not always successful, ergot 
has certainly been very useful in a considerable number of cases. 40 
I have seen very severe pain completely relieved within half an hour 
after the administration of a drachm of the fluid extract. In other 
instances, unsteadiness of the limbs, which seemed about to usher in 
paralysis, has yielded promptly to one or two doses. 
But perhaps the best evidence of its usefulness is to be found in 
the preference for it of the night-porter, who had charge of the hos- 
pital at night, and who was instructed in the use of the few medi- 
cines employed, and treated such cases as occurred among the men 
composing the night gangs. Having both morphine and ergot at 
hand, he gradually, and of his own accord, almost abandoned the 
former, declaring that the ergot was more prompt and certain in 
relieving the pains. This from an intelligent, unprejudiced, non- 
professional source, is strong testimony in favor of the efficiency of 
the drug. 
I was in the habit of giving a teaspoonful of Squibbs’ fluid extract, 
and repeating the dose in half or three-quarters of an hour, unless 
the pain was relieved. In one case ergotine was injected hypoder- 
mically ; but so much irritation was caused at the point of insertion 
that the experiment was not repeated. 
Frictions, with or without stimulating liniments, are very generally 
resorted to, and seem sometimes to give momentary relief, but it ap- 
pears to me to be rather by occupying the attention of the patient 
than by any action occasioned in the part. 
In one of my cases of pain in the knee, compression of the femo- 
ral artery with the fingers was tried. The pain was considerably re- 
lieved for a few minutes, but soon acquired its former severity. In 
another case a tourniquet was applied so as to interrupt the venous 
as well as the arterial circulation, but with no better result. 
In some instances where the pain was confined to a particular lo- 
cality, I had the part immersed in hot water, with the effect of caus- 
ing temporary relief. But the use of the general hot bath was not 
advised, as I considered it unsafe to increase the already existing re- 
laxation of the vessels. In several of Dr. Jaminet’s cases paralysis 
came on while in the hot bath, and he therefore interdicted its use. 
Toward the last of my experience I applied cold to the spine in 
twTo cases, with apparent benefit in each. In one of these cases, in 
which there was paralysis of the bladder, the improvement after a 
cold douche to the spine was marked. 
In one case of paraplegia, dry cups applied to the spine in the lum- 
bar region were unmistakably beneficial. 
Electricity was tried by Dr. Jaminet at St. Louis, but was found 
to be useless. 
Epigastric pain is almost always relieved at once by the use of an 
alcoholic stimulant with ginger, as employed by Dr. Jaminet. 41 
Vomiting is best treated with sinapisms to the epigastrium, and 
swallowing small bits of ice. A full dose of calomel was effectual 
in one of my cases which resisted all other treatment. 
When paralysis occurs, it is to be treated on general principles. 
Cups or leeches, with douches and frictions to the spine, may be use- 
ful ; and if the case be protracted, the use of strychnine may be called 
for. The bladder will almost certainly be involved, requiring the 
constant employment of the catheter. 
The cerebral symptoms which occasionally occur, are, with the ex- 
ception of coma, so transient in their nature as to call for no special 
treatment. Coma, when it takes place, is to be managed according to 
the chcumstances of the case, as when proceeding from other causes. 
If accompanied by a full, strong pulse, venesection may be expe- 
dient. 
There remains to be considered a plan of treatment originally sug- 
gested by Pol, and carried out to some extent by Foley, viz., return- 
ing the patient at once into the compressed air. 
It frequently happened under my observation, that pains not suffi- 
ciently severe to deter the men from returning to work, wTere promptly 
dissipated on entering the caisson, to return again on coming into the 
open air. Indeed, I do not remember a single exception to the rule, 
that any pain which may have been felt before, disappeared almost 
immediately on going below. 
Foley says, as the result of his experience : “A true specific is re- 
turning to the caisson, through which means all such accidents (pains, 
vertigo, etc.,) speedily disappear. It is to be resorted to unhesitat- 
ingly in all threatening cases, and the pressure should be admitted 
rapidly.” 
But the means of access to the caisson are usually such that it 
would be difficult to remove a patient into it, even if he could be 
comfortably cared for while there, or if his presence would not in- 
terfere with the wrork. It would, therefore, be desirable to have 
facilities for employing compressed air at some point above ground 
which would be easily accessible. 
My plan would be as follows : Let them be constructed of iron of 
sufficient thickness, a tube 9 feet long and 3J feet in diameter, having 
one end permanently closed, and the other provided with a door open- 
ing inward, and closing air-tight. This tube to be placed horizon- 
tally, and provided with ways upon which a bed could be slid into it. 
Very strong plates of glass set in the door and in the opposite end 
would admit the light of candles or gas jets placed immediately out- 
side. This apparatus should be connected by means of a suitable tube 
with the pipe which conveys the air from the condensers to the 
caisson. An escape-cock properly regulated would allow the constant 42 
escape of sufficient air to preserve the necessary purity of the at- 
mosphere within. 
The bed containing the patient having been slid into the chamber, 
the door is to be closed, and the pressure admitted gradually until it 
nearly or quite equals that in the caisson. This should be continued 
until the patient indicates by a signal previously concerted, that the 
pain is relieved. The pressure should then be reduced by degrees, 
carefully adjusted to the effect produced, until at last the normal 
standard is reached. By occupying several hours, if necessary, in the 
reduction of the pressure, it is probable that a return of the pain 
could be avoided. 
The apparatus once provided, there would be no difficulty in car- 
rying out the plan in any case of such severity as to resist other 
treatment. I should expect the very best results from it in cases of 
extreme pain, or in the very outset of paralysis not dependent upon 
extravasation of blood. 
Of course the secondary conditions which arise in protracted cases 
would not be capable of direct relief by simply reproducing the phys- 
ical conditions existing in the caisson. The most that might be 
hoped for in such cases would be that the pressure might result in 
giving a new impulse to the circulation in the congested part, and 
thus favor resolution. 
Reasoning from his view of the pathology of the disease, M. Bert 
lias proposed the inhalation of oxygen, in order to displace the free 
nitrogen from the blood by diffusion. Experiments upon animals 
demonstrated that the sounds produced in the heart by the presence 
of free nitrogen, speedily disappeared when the animal was made to 
inhale oxygen, the nitrogen diffusing into this gas much more readily 
than into common air. But though immediate death was averted by 
this expedient, paralysis nevertheless occurred, and post mortem 
examination showed the presence of bubbles of nitrogen in the 
vessels of the cord. 
A tendency to pulmonary congestion seems to be induced by high 
atmospheric pressure in certain rare instances. Such cases are men- 
tioned by Frangois and Jaminet, and two instances came under my own 
observation, one of which was almost instantly fatal. (Case XXX.) 
The mechanism by which these congestions are produced is not 
apparent. If in every instance they occurred immediately upon 
passing from the caisson into the open air, it might be inferred that 
the expansion of the air contained within the lung produced, in some 
way, an interference with the pulmonary circulation. But inas- 
much as a rapidly fatal congestion may come on an hour or more 
after leaving the caisson, this explanation is not sufficient. The 43 
subject is involved in obscurity, which can be removed only by the 
study of a larger number of cases than have occurred as yet. 
CHAPTER SIXTH. 
ILLUSTRATIVE CASES. 
The following cases have been selected from my notes as illustrat- 
ing the various affections resulting from compressed air which have 
been described in the foregoing text. Also, a few cases, as will be 
seen, have been borrowed from other sources. 
Case I.—John Campbell, lock-tender, on the lltli of February, wTas 
“caught in the lock, ” i. e., found himself unable to equalize the 
pressure in the left ear. The pain, however, not being severe, he 
completed his day’s work. The following night was taken with 
very severe pain in the ear, which continued without intermission 
until the 20th, when a profuse discharge of pus from the external 
ear set in, affording relief from the pain. Under the use of carbolic 
acid injections the discharge soon ceased, leaving the hearing unim- 
paired. 
Case II.—John Hicks. Taken on the 17th of May, while in the 
lock going down, with severe pain in the right ear, followed by a 
slight discharge from the external meatus. No sensation as of any- 
thing giving way in the ear. He completed his watch and then 
reported to me. On examination, the drum of the ear was found to 
be ruptured at its upper edge. The opening was nearly circular, and 
rather less than a line in diameter. The patient -preferred to give up 
his place at once, and did not report again. Though he stated that 
he had had no previous trouble with the ear, the fact of the discharge 
when the membrane was ruptured, leads to the suspicion that there 
was catarrh of the middle ear, which probably accounted also for the 
stoppage of the Eustachian tube. 
Case III.—(Frangois).* Patient at Argenteuil seized with otalgia 
on coming out of the caisson, where the pressure was 13 lbs. to the 
inch. Pain persisted for 15 days without intermission, notwithstand- 
ing the most active treatment, including purgatives and the applica- 
tion of leeches and antimony behind the ear. Condition of the 
tube or of the drum not stated. 
Case IV.—Patrick O’Farrell. Reports March 11th, that he was 
taken four days ago, on going down into the caisson, with pain in 
the region of the frontal sinus. On coming up, the pain was in- 
creased, and there was bleeding from the nose. The pain has con- 
tinued ever since. Ordered anodynes and hot fomentations. 
* Annales d’Hygiene Publique, et de Med. Leg. T. XIV. 1860. 44 
14th. Reports for duty. 
Case Y.—Hugh Rourke. March 12tli, while going home in the 
evening, was taken with severe pain in the right knee. Pain continued 
all night. On the following morning he returned to his work, when, 
on entering the caisson, he found that the pain ceased at once. On 
coming up again it returned with increased severity. Controlled by 
morphine. 
Case VI.—John Roland. Taken on March 8th, while in a car 
going home. Dizziness and loss of strength; feet cold, head hot; 
unable to stand, but still not paralyzed—simply weak. No pain. 
Profuse cold perspiration. Recovered perfectly in a few hours with- 
out treatment. 
Case VII.—Alfred Symes. Suffered somewhat with pain in the 
right knee, on coming up from the caisson on the 10th of May. On 
the lltli he worked as usual, experiencing no pain. On the 12th 
(Sunday), not having been in the caisson since the day previous, he 
was taken wdtli severe pain in the same knee. When he reported to 
me, on the 14th, he was suffering with a swelling of the knee, ac- 
companied by heat and extreme tenderness, especially just above the 
patella. He was ordered to apply fomentations, with a hot solution 
of bicarbonate of potash. Under this treatment the pain and swell- 
ing soon subsided. On the 15tli, there was a greenish yellow tinge 
of ecchymosis over the front of the knee, for a space as large as the 
palm of the hand. 
Case VIII.—Samuel Mitchell. Worked for one watch only on the 
14tli of May, being his first experience in compressed air. After the 
first watch, on the 15th, he was taken with pain in both the upper 
and lower extremities, and also in the chest and bowels. This was 
followed by giddiness and vomiting. There was paralysis of the left 
leg and weakness of the right arm. Profuse sweating. Pulse 80. 
Ergot and chloral given. Paralysis passed off in two hours, leaving 
slight pain in the arms and wrists. The bowels had not been opened 
for several days. 
Case IX.—John Kennedy. This patient had engorgement of the 
left mammary gland, recurring each day after coming out of the 
caisson, and especially after the second watch. There wTas marked 
swelling and tenderness, which disappeared during the afternoon and 
evening, to recur again ou the following day. This continued for 
more than a week. 
Case X.—Joseph Hatch. Taken sick on the 17th of May, after 
his first watch. Epigastric pain and pain in the legs and arms, fol- 
lowed by paraplegia. Treated with ergot only. At the end of four 
hours he had recovered the use of his limbs, and the pain had ceased, 
but there remained a giddiness which prevented his standing. By 45 
the following day he was able to walk about, but the giddiness had 
not entirely disappeared when I last saw him, May 21st. 
Case XI.—E. Riley. Taken sick Feb. 16th, one hour after leaving 
the caisson. Pressure 26 lbs Epigastric pain and pain in the legs. 
No loss of sensibility. Profuse cold perspiration. Pulse, when I saw 
him, two hours after the commencement of the attack, was 96. The 
pain, which at first W’as very severe, had by this time become much less. 
Gave him an ounce of brandy and a teaspoonful of fluid extract of 
ergot. In 10 minutes the pulse, had fallen to 82. Was able to resume 
work next day. 
Case Nil.—Joseph Brown, foreman, American, aged about 28. 
Taken on the 28tli of February, about an hour after coming up from 
a three hours’ watch. Excessive pain in left shoulder and arm, com- 
ing on suddenly, “like the thrust of a knife.” Pain continued until 
he went down again for the afternoon wratch, when it ceased imme- 
diately. On the following morning there was a spot on the shoulder 
and one on the arm, at the points where the pain had been most 
severe, where the skin was speckled with minute bright red points of 
extravasated blood. Had had no pain since the day before, but the 
parts were tender to the touch, with at the same time a feeling of 
numbness. 
Case XIII.—Henry Stroud, a diver by occupation, began work on 
the morning of April 2d. Half an hour after coming up from the 
first watch, was taken with numbness and loss of power in the 
right side, also dizziness and vomiting. This was followed by severe 
pain over the whole body. Excessive perspiration. Was treated 
with stimulants and ergot, and in five hours was well enough to re- 
turn home. 
Case XIV.—John Barnabo, Italy, 42, reports that on the 13th of 
March, while in a car returning home, he was taken with severe pain 
in both arms. This was followed by dimness of sight and partial 
unconsciousness. Extremities very cold. Remained in this condi- 
tion for two hours. Was obliged to keep his bed for three days. 
For a week afterward was unable to work, feeling very much op- 
pressed about the chest. Had no medical attendance. Had a simi- 
lar but less severe attack about a month previously. 
Case XV.—J. Avers. Taken on the 7th of April with very severe 
pain in both knees, coming on within a few minutes after leaving the 
caisson. A drachm of the extract of ergot was given every hour for 
three hours, then two more doses at intervals of two hours, after 
which he was completely relieved. 
Case XVI.— Frank Murphy. Taken sick April 8tli, after the sec- 
ond watch of his first day in the caisson. Extremely severe pains in 
both knees and in the right shoulder; of a grain of atropine was 46 
injected beneath the skin of the shoulder, but afforded no relief. 
Half a grain of morphia by the mouth did not check the pain. Legs 
placed in hot water, which gave immediate relief. Ergot was also 
given in drachm doses hourly. Returned home much better, but the 
pain subsequently returned, and was very severe at times for several 
days. 
Case XVII.—Charles Peterson. Taken on the 11th of April with 
severe pain in both legs and in the right arm. Was relieved by ergot, 
but had severe pain each day afterward on coming up. On the 15tli 
he was ordered a teaspoonful of the fluid extract of ergot, four times 
a day, after which there was no further complaint. 
Case XVIII.—Card, foreman. Taken on the 17tli of April, after 
the first watch, with quivering in the thighs, followed by loss of 
power in the lower extremities, and anasthesia. There was 
also partial paralysis of the bladder. These symptoms con- 
tinued until the 19tli, when they disappeared, leaving great sore- 
ness of the muscles of the calves. After the paralysis had passed off 
in a measure, he went down again into the caisson and remained for 
a short time with decided benefit. The improvement continued after 
returning to the open air. He had no other medication than two 
doses of ergot. 
Case XIX.—James Ileffener. Attacked May 2d, soon after leav- 
ing the caisson, with pain in the limbs and in the epigastrium, fol- 
lowed by vomiting of large pieces of undigested meat. Eyes swollen 
and very much injected; extreme giddiness; pulse 80, and small. 
Vomiting continued at intervals for 24 hours. Bowels had not been 
moved for 48 hours. 
Was treated with morphia and ergot, but the vomiting continuing, 
a scruple of calomel was given on the 3d, which had the effect of 
quieting the stomach, and at the same time of relieving the bowels, 
after which the patient quickly recovered. 
Case XX.—Thos. Kirby. . Taken April 30, with severe pain in 
the right forearm. The patient was seen by Dr. G M. Beard, at 
whose suggestion I injected into the middle of the palmar aspect of 
the forearm two minims of a solution of ergotine, each minim con- 
taining a grain of the drug. The following day, considerable swell- 
ing had taken place at the point of puncture. The original pain still 
continued, though less severe. On the 4th day of May, the patient 
presented himself with a similar, though more extensive, swelling on 
the other side of the arm, the previous swelling having disappeared. 
This secondary swelling followed very closely upon the first. It sub- 
sided promptly under the use of cold applications ; but on the 10th, 
another similar swelling appeared on the part of the arm above the 
elbow. It was excessively hot and painful. By the continuous use 47 
of ice, it was soon dissipated without suppuration. The patient did 
not enter the caisson from the time of the first attack until his final 
recovery. 
Case XXI.—Brune Wieland, Germany, aged 23. Attacked on the 
8th of May, after working two hours in the caisson, which he entered 
for the first time, and without having taken food. The attack began 
with pain in the epigastrium, and vomiting soon followed by para- 
plegia, and great depression. Respiration 40, pulse 100, and very 
feeble. Stimulants brought about a prompt reaction. The power of 
motion was soon regained, but there was not sufficient strength in the 
legs to stand. Paralysis of the bladder. On the following day he was 
perfectly comfortable, though still too weak to stand. Bladder still 
paralyzed. Sent to the hospital, after which there is no record of his 
case. 
Case XXII.—Patrick Rogers, Ireland, aged 40, reported at my 
office at the pier that the day previous he wTas taken wiiile on the 
ferry-boat going home, with pain in the right side, soon followed by 
loss of feeling and power to move or stand. This wras about three- 
quarters of an hour after leaving the caisson, where the pressure was 
26 lbs. to the inch. On the arrival of the boat he was placed in a 
hack, and taken home. According to his account, he was for four 
hours completely paralyzed in the legs, and partly so in the arms. A 
physician was called, who gave a medicine which caused vomiting, 
after which there was profuse cold perspiration. Symptoms grad- 
ually passed off, and by 3 P. M. of the following day he was well, 
with the exception of weakness and a numb feeling of the skin. A 
drachm of the fluid extract of ergot was ordered to be given every 
hour until four doses had been taken. On the 17th, he reported him- 
self as much better. Soon after taking the first dose of ergot, he 
found his strength improved. He now felt well, except a “trembling ” 
in the chest. Advised not to resume wrork in the caisson. 
Case XXIII.—Charles Ward. Began wrork May 17th, and con- 
tinued through both watches, though advised to omit the afternoon 
watch for the first day or twro. After coming up the second time, he 
felt some pain in the legs. Did not work again until the 20tli, when, 
after the first watch, he was taken with numbness in the left leg, 
and partial loss of motion. When I saw him on the 21st, the sensi- 
bility in the affected part wTas very much blunted, but the power of 
motion was fully restored. Temperature to the hand sensibly lower 
than in the other leg. Xo pain. Complaint of a “want of hold 
upon the ground ” in attempting to walk. 
Cold water was poured upon the lower part of the spine for several 
minutes, after which there was a decided improvement in the leg. 
He was able to walk home; but did not report again, and I lost sight 
of the case. 48 
Case XXIY.—Fred. Wilkinson. Taken May 21st, after the second 
watch, with pain in the right knee. Considerable swelling above 
and internal to the patella. Slight elevation of temperature. Re- 
lieved by the cold douche. 
The minutes of the following case were kindly furnished me by 
Dr. Walter Reed, of the Brooklyn City Hospital, and are so interest- 
ing that I transcribe them in full: 
Case XXV.—“Michael Madigan, age 36, Ireland, laborer, admitted 
March 26tli, 1872. A large, robust man; states that he has been 
working on the East River Bridge for three months past, and that 
for several wTeeks past has been under a heavy atmospheric pressure 
(about 30 lbs.) 
“March 25th, about noon, after coming up from the caisson, was 
taken with cramps in his stomach, which required a dose of medi- 
cine for their relief. He then went to his dinner, after which he re- 
turned to work, but felt so weak in the legs and in the small of the 
back that he was compelled to leave off. Was carried home and put 
to bed. Did not have much pain in the legs or back, but a feeling of 
extreme weakness. Slept but little during the night, and in the 
morning found that his legs were powerless, nor could he pass his 
wTater, which had to be drawn with a catheter. On admission there 
was found to be paralysis of the legs, with slight diminution of 
sensibility. No pain in limbs. Slight tenderness on pressure over 
the lumbar vertebras. Paralysis of bladder. Urine drawn off; 
quantity, 8 oz. Acid reaction ; no albumen. Dry cups applied to the 
lower part of the spine. Ordered liq. amnion., acetatis, to be re- 
peated in an hour. At bed time potas. bromid. grs. 40. 
“March 27tli. Find patient improved. Slept well during the night. 
Took some breakfast. Can move his right leg to a considerable ex- 
tent ; left leg powerless. Has slight pain in the back. Urine drawn 
off, 8 ozs.; acid. P. M., to re-apply dry cups to spine. 
“March 28th. Can move both legs very well. Is able to stand, but 
his knees soon bend under him. Urine drawn off. Cups re-applied. 
“March 29tli. Can stand up and walk a few steps, though this re- 
quires some exertion. Cups again to the spine. Urine drawn off. 
“March 31st. Still improves; walked to the water-closet and had a 
movement of the bowels. This is the second movement since admis- 
sion. The first was an involuntary evacuation in the bed. 
“April 2d. The patient lias regained the power over his bladder, 
and passes his urine twice a day. Feels much stronger. 
“April 5th. Patient has been walking about the yard. Says he 
feels well, except a slight weakness in his back. Discharged cured.” 
For some time after his discharge from the hospital, this patient re- 
mained very feeble, and the catheter was occasionally required to re- 49 
lieve the bladder. He was confident that he received great benefit 
from the dry cups while in the hospital, feeling better each time as 
soon as they were applied. In this statement Dr. Reed concurred. 
Case XXYI.—Reardon, England, 38, corpulent, began work on 
the morning of May 17tli; was advised to work only one watch the 
first day, but, nevertheless, feeling perfectly well after the first 
watch, went down again in the afternoon. The pressure at this time 
was about 35 lbs., the duration of the morning shift 24 hours, that 
of the afternoon shift 2 hours. Immediately after coming up from 
the second watch Reardon was taken with very severe pain in the 
stomach, followed by vomiting. In a few minutes the pain seized 
upon the legs, which soon lost the power of motion, though they con- 
tinued to be the seat of extreme pain, and were not entirely insensi- 
ble to pinching or pricking. The vomiting continued all night, and 
toward morning he was removed to the Centre street Hospital, where 
he gradually sank, and on the 18th died. 
The autopsy showed a slight engorgement of the lungs. All the 
other thoracic and abdominal viscera, as well as the brain, were 
healthy. The spinal cord was found to be intensely congested, and 
opposite the two lower dorsal vertebrae, there was an extensive effu- 
sion of blood pressing upon the cord. 
Case XXYII.—Patrick McKay, Ireland, 50. Had been four months 
at work in the caisson, and had not complained of ill-health. On the 
30th of April he remained in the caisson half an hour beyond the 
usual time, at the second watch, the pressure being about 34 lbs. 
Some other persons who were with him in the lock, when about leav- 
ing, found that he was sitting with his back against the wall of the 
lock, quite insensible. He was at once carried up to the surface, and 
removed to the Park Hospital, where I saw him shortly afterwards. 
He was there in an unconscious condition ; face pale and dusky ; lips 
blue ; pulse irregular and feeble. Under the administration of stimu- 
lants, he recovered some degree of consciousness, and begged inces- 
santly for water. The urine was drawn with a catheter, and found 
to be intensely albuminous. Paroxysms of convulsions soon set in, 
in one of which he died, nine hours after the attack. 
The autopsy, at which I was not present, showed that all the 
organs were healthy, except the kidneys, which were the seat of 
Bright’s disease, and were very much altered in structure. 
In this case the effect of the compressed air was merely to hasten 
an event which, at best, could not have been very long delayed. 
Case XXVIII.—(Frangois). Mirant. Had suffered previously 
from severe pains in the chest and limbs, which compelled him to 
give rip work. Sometime afterward, when the pressure was 4 at- 
mospheres, he resumed work for a single day—the labor being exces- 50 
sively severe. He suffered no inconvenience apparently, however, 
and after leaving the caisson, washed his face and hands as usual. 
A moment after he fell senseless, and in 15 minutes was dead. 
The autopsy was made by a medical commission appointed by the 
authorities of Valenciennes. The menniges were found to be inject- 
ed, and the sinuses distended with dark blood. The brain itself was 
also congested. Tiie spinal canal was not opened. The lungs were 
somewhat congested, especially at the base, where they were less 
crepitant than natural, though still floating in water even when cut 
into small pieces. There was general congestion of the abdominal 
viscera. (Annales d’Hyg. de Pub. et Med. Legale, 1860.) 
Case XXIX.—The following description of the post-mortem ap- 
pearances in a case occurring at St. Louis, is from Dr. Jaminet’s re- 
port, and may be taken as a type of the morbid anatomy of the Cais- 
son Disease. 
“Henry Krausman, 27 years ; nativity, Germany ; admitted into 
the hospital March 22d; died the 23d. The whole contents of the 
cranium were found highly congested, with effusion beneath the 
arachnoid, the vessels of the latter membrane being highly injected. 
Blood oozed freely from the substance of the brain on section. The 
spinal cords presented pathological conditions precisely like those of 
the brain, with the addition of the existence of clots of extravasated 
blood at different points inside the dura mater. There wras also a 
congested condition of the thoracic contents, less marked probably in 
the lungs than in the other organs. The abdominal viscera were 
very highly congested, with extravasation of blood in the kidneys 
The mucous membrane of the bladder was healthy, and a small 
quantity of bloody urine was in the bladder.” 
Case XXX.—John Myers, aged about 40 years, a native of Ger- 
many, of a stout, heavy build, commenced wrork in the caisson for 
the first time on the 22d of April, 1872, the pressure then being 
about 34 lbs. to the inch. 
lie worked during the morning shift of 24 hours without in- 
convenience, and remained about the yard for nearly an hour after 
coming up. He then complained of not feeling well, and started for 
his boarding-place, -which -was but a few rods distant. As he passed 
through the lowrer story of the house, on his wray to his own room, 
which wTas on the second floor, he complained of pain in the abdo- 
men. While ascending the stairs, and when nearly at the top, he 
sank down insensible, and was dead before he could be laid upon his 
bed. 
The autopsy, which took place at the morgue, was made by Dr. 
Janeway. It showed that the brain, heart, kidneys, and larynx were 
perfectly normal. The only lesion discovered was in the lungs, which 51 
were congested to a very remarkable degree. The entire extent of 
both lungs presented an appearance closely resembling that of a 
highly congested spleen. The spinal canal was not opened; but 
nothing was found elsewhere to account for the sudden engorgement 
of the lungs. 
CHAPTER SEVENTH. 
As it is now demonstrated that the method by compressed air is ap- 
plicable to a great range of engineering operations, and offers many 
peculiar advantages, it is extremely desirable that the principal ob- 
jection to its employment, viz., the discomfort and danger to the 
workmen, should be reduced to a minimum. To this end I would of- 
fer the following suggestions, drawn from my own experience and 
that of European and American observers, to whose writings I have 
had access. 
It is exceedingly desirable that the men should be under control to 
a certain extent during the intervals of work. Excessive use of in- 
toxicating liquors should be prevented; regular hours for sleep and 
for meals insisted upon, and sufficient nutritious, digestible, and 
properly cooked food should be provided. The men should sleep in 
comfortable beds and in properly ventilated apartments. 
All this is manifestly unattainable if the men live in homes of then- 
own choosing. If, therefore, any great work by the aid of com- 
pressed air is to be undertaken, the preparations for it should include 
whatever is necessary for housing and feeding the men at a conven- 
ient place near to the work. For this purpose temporary barracks 
may be erected in an enclosure, which the men should not be permit- 
ted to leave except under proper restrictions. 
The food should be furnished by the employers, be of good quality, 
embrace a sufficient variety, and be prepared by competent cooks. 
Sleeping apartments should he provided, allowing at least 800 cubic 
feet of air-space to each man, and with facilities for efficient ventila- 
tion. 
A hospital should be arranged with a sufficient number of beds, 
and fitted with every appliance necessary for treating patients during 
their entire illness. The hospital to be in charge of a competent 
steward, under the supervision of a physician, who should attend a 
portion of each day. 
Of course this implies that only single men shall be employed, and 
that they shall agree at the outset to submit to a quasi military 
rule. 
SUGGESTIONS. 52 
Where the number of men is considerable, as would be the case in 
any large work, the company could carry out the above suggestions 
economically to themselves, and after deducting the cost from the 
pay of the workmen, there would remain to the latter more than 
they would have left after paying their board in the usual Avay. At 
the same time the men would be so much more comfortable than if 
left to provide for themselves, that they would value the position, 
and the fear of being discharged would be a sufficient restraint upon 
them. The tendency, too, would be toward securing at the begin- 
ning of the Avork a set of men who would continue to the end. These 
men commencing AArhen the pi’essure Avas slight, would not be affected 
by its gradual increase, thus avoiding the great danger Avhich attends 
those avIio begin Avork for the first time after the pressure has at- 
tained a high figure. I am satisfied that it is by attention to this 
point more than by anything else, that the suffering and danger re- 
sulting from the use of compressed air may be diminished. (See 
page 36.) 
New hands should not be alloAved to work in the caisson more 
than one watch in each day for the first Aveek, after which half the 
usftal second Avatch might be added for another Aveek, at the close of 
which the full time could be entered upon. 
Since much of the work on the pier above, as Avell as in the caisson 
below, is unskilled labor, it could readily be so arranged that the 
gangs could work on alternate days in the compressed and in the 
external air. The advantage of an interval in the caisson work is 
immediately apparent, the cases of sickness being notably diminished 
by even a single day’s intermission. 
The rules given at p. 15 are important, and their observance 
should be strenuously insisted upon. 
The men should be selected as far as possible from those avIio are 
of a spare and wiry build, and no one should be accepted avIio has a 
tendency to corpulency. 
The lock-tenders should be selected Avitlx special reference to their 
trustworthiness, and, if it is found that they cannot be depended 
upon, the air-cocks should be so arranged that the aperture can be 
graduated from time by the engineer in charge, so as to prevent the 
possibility of a too rapid change of pressure. 
In entering the caisson, at least three minutes should be alloAA'ed in 
the lock for each additional atmosphere of pressure, and at least five 
minutes in coming out. 
As for the number of hours of Avork daily, the rule given by Mr. 
Collingwood Avill serve as a general guide. “ Taking it for granted 
that 12 hours is the extreme time that a man can labor Avithout detri- 
ment to health, in an ordinary atmosphere, then with a pressure of 53 
two atmospheres, or 15 lbs. additional pressure, he can labor about 
one-half that time ; with three atmospheres, about one-tliird of that 
time ; and with four atmospheres about one-fourth of that time. In 
other words, the time is inversely as the pressure.”* 
Whenever, for any cause, a sudden increase of pressure is demand- 
ed, the watch should be shortened to a corresponding extent. 
The air-locks should be placed at the top rather than at the bottom 
of the shaft, in order that the stair may be climbed in the compressed 
air, instead of immediately after leaving the lock, when the system 
is more or less prostrated by the change taking place in the circula- 
tion. If, for any reason, it is impracticable to have the air-lock at 
the top of the shaft, an elevator should be employed to lift the men 
to the surface. 
Care should be taken to maintain the air in the caisson at a suffi- 
cient degree of purity, as there may be a wide difference between 
the amount of air required to supply the necessary mechanical condi- 
tions for carrying on the work, and the quantity demanded for the 
health of the workmen. A rough but useful test for the presence of 
carbonic acid in the air has already been described at p. 14. This is 
very easily applied, and should be frequently resorted to when there 
is the least doubt as to the sufficiency of the air supply. A compari- 
son of the results with those obtained in some fairly ventilated 
apartment, will give an idea of the amount of impurity in the air of 
the caisson. The comparison will be aided by allowing the carbonate 
of lime formed to settle to the bottom of the test tube, where the 
quantity can be more readily appreciated. 
ANDREW II. SMITH. 
* Trans. Am. Society of Civil Engineers, p. 133.