Compressed Air; Low Pressures 769 



the diaphragm drops at the same time as the abdominal wall, fol- 

 lowing the retreat of the intestines. 



For the purpose of confirming this and of measuring the in- 

 crease thus gained, I made the following experiment: 



A dog was killed by section of the medulla; immediately after, 

 his thoracic capacity was measured by the accurate procedure de- 

 vised by M. Grehant; 5 then there was introduced into his 

 trachea a tube in the shape of a Y, one of the branches of which 

 opens into the air, while the other communicates with a rubber bag 

 carefully emptied of air; two valves arranged in opposite directions 

 permit the outer air to enter by the first branch, whereas it cannot, 

 once it has entered the lungs, escape except through the second 

 branch into the bag. When these arrangements had been made, 

 the body of the animal was placed in a compression apparatus. Its 

 lungs, in communication with the air, could undergo the changes 

 in capacity the existence of which we were seeking to verify. Then 

 a sudden decompression was made; the air in the lungs, which was 

 then in excess, escaped and lodged in the bag, where we could 

 measure its volume, which would indicate whether there was an 

 increase in the thoracic capacity. 



Here is the simple formula which serves to find and calculate 

 this increase. 



Let us call the pulmonary capacity at normal pressure C, the 

 compression (total number of atmospheres) to which the animal 

 was subjected P, and the volume of air found in the bag after the 



C + V 



decompression V. It is evident that the formula will repre- 



P 



sent the pulmonary capacity during the compression, and the com- 

 parison of the number thus obtained with C will show the value 

 of the increase. 



When this had been established, I ligated the intestinal tube at 

 its two ends, anus and esophagus, and collected the gases from it 

 under water; it was interesting to see the relation between their 

 volume and that of the thoracic variations. 



Experiment CCCXXIX. June 27. Dog of 4.250 kilos, which had 

 just been poisoned by curare. 



It was placed, prepared as was just explained, in the cylindrical 

 apparatus, and the pressure was raised to 3 atmospheres; after the 

 decompression there were 260 cc. of air in the bag. 



The lungs and trachea of the animal, carefully extracted, and 

 macerated under water, after being cut into pieces so small that the 

 fragments sank to the bottom of the water, gave up only 115 cc. of air. 



