158 



CARBON DIOXIDE IN EXPIRED ALVEOLAR AIR, 



As it was thought that removing the samples from the brass 

 tube might bring about a mixing of the contents, which might 

 obscure any slight diiference in the composition of the air in the 

 several portions of the brass tube, the apparatus was varied by 

 making the brass tube in separate portions connected together 

 by rubber-tubing, which could be clamped so that each part of 

 the brass tube could be isolated. Four portions of brass tubing, 

 of 12 mm. bore and 79 cm. length, holding about 100 c.c, were 

 fitted near the centre with capillary tubes for withdrawing 

 samples of the gas. These tubes were placed in series as a, b, c, 

 and d, and connected w ith a mouthpiece 5 cm. long. The last 

 portion (d) was connected with a brass tube similar to that 

 used in the earlier experiments. This brass tube was one metre 

 long, and, to its end, two metres of rubber-tubing were attached. 

 These later experiments were performed in the same way as the 

 earlier ones. As soon as the subject had breathe'd into the tube, 

 the clamps between the successive brass tubes were tightened, 

 and the samples collected. The results of some experiments are 

 recorded in Table viii. 



Table viii. 



* After exercise. t After a deep inspiration. 



In most experiments, the expired air was expelled as rapidly 



