396 Historical 



For my part, I have been able to make a rather large number of 

 observations on this point; when a diver was on the bottom a short 

 distance from the boat, and when the sea was calm, I clearly saw 

 the bubbles of air from each respiration coming to the surface. As 

 one could see in the description of the regulating air bag, the diver 

 with the Denayrouze suit breathes through his mouth air contained in 

 a reservoir, and he expires also through the mouth. The air thus ex- 

 pired escapes through a valve which closes immediately after the 

 expiration. The time separating two respiratory acts can therefore be 

 measured in this way, and during this time the diver is under the 

 normal conditions of work and does not know that he is being 

 observed. I have thus been able to note individual differences, but 

 within very narrow limits. The minimum number of respirations was 

 12; the maximum 30; but we should not think that the average is the 

 number halfway between these two numbers. Taking all the obser- 

 vations I have made, the average is 18, but it is too high and cannot 

 give the normal number of inspirations in compressed air. In fact, 

 every time I observed in a diver a respiratory rate higher than 20, 

 I am sure that this respiratory acceleration resulted from a chance 

 cause (emotion, muscular effort, rapid walking, etc.). In many cases, 

 after following the respiration of the diver for a few minutes, I saw 

 it dropping little by little and finally getting below 20. 



In summary, the physiological modifications of the respiratory 

 apparatus affect the extent and the rhythm of the movements. Let us 

 add to what we have said on this subject that respiration is always 

 very easy in compressed air. In this we agree with all who have 

 carried on experiments under good conditions of ventilation. Under 

 the water, whatever the depth, one breathes easily and freely (P. 19) . 



We have seen in divers that the respiratory movements increase 

 in number as the men ascended the ladder and were consequently 

 decompressed. A great part of this acceleration must no doubt be 

 attributed to the very act of decompression, for the ascent is extremely 

 easy for the divers; and because of the air contained in their suit, 

 which expands as the ascent continues, they need rather to hold 

 themselves down than to make efforts to ascend. But however great 

 is the pressure undergone, this acceleration of the respiratory move- 

 ments never goes as far as panting (P. 21.) 



Let us turn to the circulation: 



In diving suits, only inexact observations can be made in this 

 regard; the pulse is very hard to take and there is no way of meas- 

 uring exactly the time occupied in the observation. Nevertheless I 

 tried to find the rhythm of my circulation, and I think that its rate 

 never dropped. 



We may say, without trying to explain it, that in compressed air, 

 at pressures used by sponge divers, the circulatory rhythm does not 

 seem altered. 



This is not true of the amplitude of the pulsations; in this all 

 experimenters, except Junod alone, agree. They all admit that in 

 compressed air the pulse becomes filiform and sometimes impercep- 

 tible .... 



