Compressed Air; Low Pressures 775 



The experiment is summarized as follows. 



Minimum Maximum Average Respiratory Number of 



Pressure Pressure Pressure Oscillations Respirations 



Tracing A 5.2 cm. 7.2 cm. 5.8 cm. 3 to 10 mm. 48 



Tracing B 8.8 cm. 13.4 cm. 10.4 cm. 16 to 23 mm. 28 



Tracing C 8.0 cm. 11.0 cm. 9.8 cm. 3 to 14 mm. 40 



Now comes the question: What is the reason for these variations 

 in the circulatory phenomena? Should they be attributed to the 

 action of the superoxygenated blood on the heart and the nervous 

 system which controls this organ and the movements of respira- 

 tion? Or, on the contrary, are they the consequence of the decrease 

 in volume of the intestines, reacting on the play of the intra- 

 thoracic organs? 



We might discuss this point at length. The surest method is to 

 experiment. If we take the arterial pressure tracings of a dog 

 which breathes first ordinary air and then air with an oxygen con- 

 tent of about 35%, which corresponds nearly to the tension obtained 

 in our compression apparatuses, we find that in spite of a certain 

 slowing down of the respiratory movements, when the animal is 

 breathing the superoxygenated air, the arterial pressure is not mod- 

 ified, and that the play of the thorax influences it equally in both 

 cases. 



It becomes evident by comparison of these results that: 



1). The pressure of the blood (maximum, minimum, average) 

 has increased in compressed air; 



2) . The variation due to the respiratory influence has increased 

 considerably in compressed air, which is contrary to the conclusions 

 of Vivenot, which were based, moreover, on observations made on 

 emphysematous patients; 



3) . These variations were accompanied by a slowing down of 

 the respiration; 



4) . They are due not to the action of the oxygen absorbed in 

 greater quantity by the blood, but to the pressure, as an agent of 

 the mechanical type. 



2. Prolonged Stay in Compressed Air. 



In this second section I shall enumerate the experiments which 

 were designed to determine whether a slight increase in the oxygen 

 tension can act favorably or unfavorably on the life of animals, on 

 their development, in a word, on the phenomena of their existence 

 as a whole, outside all physiological analysis. To study this im- 

 portant question, I experimented upon eggs, cocoons, small air- 



