Theories and Experiments 455 



brings the blood in contact with a greater quantity of the two constit- 

 uent elements of the air in the same volume, must of necessity 

 decarbonize a greater quantity of blood than under ordinary condi- 

 tions. For the same reason, the part which the nitrogen may play in 

 the body should also be more completely filled. Every inspiration 

 therefore should have a more extensive effect in compressed air than 

 in ordinary atmosphere: hence the necessity of less frequent inspi- 

 rations to satisfy the customary needs; hence a decrease, often very 

 great, in the action of the pulmonary organs, and the source of a rest 

 which is so useful and yet so hard to secure in any other way for 

 organs whose action must be incessant. 



Because of relations uniting respiration with the heart beats, the 

 slackening of the former must cause a similar change in the circu- 

 lation; many data, moreover, permit us to attribute to compressed air 

 a direct sedative effect on the circulatory system; under this double 

 action, the slowness of the pulse becomes a permanent condition, not 

 only during the continued use of compressed air baths, but even a 

 long time after their discontinuance .... 



At the same time, the appetite increases, the digestive functions 

 go on regularly, and therefore good nutrition, the undoubted source 

 of an increase in the general strength, is assured .... 



The secretions show few signs of the effect of compressed air. I 

 have noted a perceptible increase of the saliva while the baths were 

 being given. (P. 60.) 



In his second edition, published in 1868, Eug. Bertin reproduces 

 purely and simply (p. 97) the summary which we have just quoted. 

 Moreover, if- we exclude the medical observations, much more 

 numerous than in the first edition, we find very few changes from 

 the original text. 



The most important addition is the criticism of the opinion of 

 Vivenot about the slowing of the heart rate. Bertin first remarks 

 that he has rarely observed this decrease in the apparatus; on the 

 contrary, he noted it after the bath, almost always several hours 

 after, or even the next morning before the patient had risen. Often 

 it does not exist at all. Finally, it is not proportionate to the pres- 

 sure, he says, for then it would be enormous in caisson workers. 



We saw above that Hoppe, 17 in a notable work on the causes of 

 the death of animals killed suddenly by rarified air, had found in 

 their blood vessels bubbles of free air, to which, in his opinion, the 

 death was due. He did not fail to apply to the symptoms of sudden 

 decompression the observation which he had made: 



If, after an animal has remained for some time in compressed air, 

 the pressure is suddenly lowered, the lungs will not have time to 

 allow the gases which have been freed in the large veins to escape. 

 That is why sudden deaths, without anatomical lesions, have occurred 

 in the coal mines of France. (P. 72.) 



