RESPIRATION OF DIFFERENT GASES. 
737 
a point is reached a1 which the partial pressure of oxygen becomes 
dangerous to life. When the arterial blood contains a third more than 
its normal quantity of oxygen, the metabolism of the body diminishes 
greatly, and the animal dies. The following examples will illustrate 
this effect : — 
Duration of the 
Compression. 
Pressure in 
Atmo- 
sphen -. 
Pressure of 
i ixygen 
in Atmo- 
spheres. 
Composition 
of Gases of Blood. 
Rectal 
Tempera- 
ture. 
Remarks. 
OxP 
•20V 
2 . 
CO,. 
45 min. 
65 min. 
Air. 
IS 
7 
Free air £7 
min. after. 
Free air 67 
min. after. 
Air. 
Oxygen. 
6 
9 
Air. 
5 
Air. 
7 
25 
4-4 
•24 
35 
21 
21-5 
14-9 
21-4 
32-5 
16-9 
17-0 
19-8 
20-9 
26-3 
30-7 
31-1 
34-3 
73-8 
21-0 
31-5 
20-9 
34-5 
63-5 
61-5 
38° -5 
39°0 
38°-5 
33° 
Dog : 
convulsions; 
survived. 
> 
-Dog; 
death. 
j 
/'Sparrow ; 
I convulsions; 
"\ death in 30 
t min. 
j' Sparrow ; 
| convulsions 
I death in 20 
\. min. 
The practical importance of these experiments in connection with the symp- 
toms observed in men after working in caissons is obvious. Details of nirrner- 
ous cases are given by Paul Bert * and others, 2 but here it is sufficient to draw 
attention to the chief symptoms and changes observed hi men working in 
compressed air. The earliest and most constant symptom is pain and noise in 
the ears, due to the pressure upon the tympanum ; relief is generally obtained 
by swallowing, or by a forced expiration with closed nose and mouth ; in some 
cases, however, the tympanum has been ruptured. The respiration is slower 
and deeper. The danger to life, liOAvever, chiefly occurs when the workmen 
leave the caisson and come out into the fresh air ; the symptoms then observed 
are due to the relative fall in atmospheric pressure, and are chiefly these — 
very painful itching of the skin, painful swelling of the muscles and joints, 
disturbances in locomotion and sensation, paralysis of the lower limbs, 
bladder, and rectum, and more rarely extensive paralysis, unconsciousness, 
and sudden death. 
1 Loc. cit., p. 369. 
2 See ref. given by Paul Bert, loc. cit. ; E. H. Snell, "Compressed Air Illness or so- 
called Caisson Disease," Londou, 1896 ; Heller, Mager, Schlatter, Centralbl. f. Physiol., 
Leipzig u. YVien, 1896, No. 2, S. 40 ; Friedrich and Tauszk, lFien. Tclin. Rundschau, 1896, 
S. 233. 
VOL. I. — 47 
