Compressee Air; Low Pressures 771 



more, in Experiment CCCXXXI, with only a third of an atmos- 

 phere, it was 8%. That is easily understood, because in its descent 

 upon the abdomen the diaphragm must meet more obstacles than 

 the walls of the belly. 



E. Intra-Pulmonary Pressure. 



We have known for a long while that at the beginning of the 

 inspiration, the air contained in the chest is a little rarefied, and 

 that it is a little compressed at the beginning of the expiration, that, 

 in other words, as I have said elsewhere, "the glottis does not suf- 



Fig. 66 — Apparatus for the observation of variations of the intrapulmonary 

 air tension. 



fice for the output of the respiratory pump." Are these variations 

 in the intra-pulmonary pressure, which have such an important 

 influence on the course of the blood the same in compressed air as 

 in normal air? We have seen that Pravaz did not hesitate to con- 

 sider them increased; but he did not furnish, any more than 

 Vivenot and the other doctors who adopted his opinion, any ex- 

 perimental proof to support his word. To study this difficult ques- 

 tion, I used an experimental method which I published long ago. 6 

 An animal is placed under a tubular bell which is well ground 

 to fit its base (Figure 66), through the stopper of which passes an 

 elbow tube, which is attached to a Marey polygraph by a rubber 



