248 COMPARISONS OF RESPIRATORY EXCHANGE. 



made by Mr. H. L. Higgins, which showed that with quiet, regular 

 respiration there was practically no difference in composition. 



From these experiments and the alcohol check tests it would appear 

 that the uniformity in the composition of the air throughout the 

 spirometer depends upon the character of the respiration. In the 

 alcohol check tests the volume per respiration produced by the hand 

 spirometer was very small, so that the movement was not sufficient 

 to cause so complete a mixing of the air as in normal respiration. In 

 the comparison experiments in this research in which the Tissot appa- 

 ratus was used, the respiration was quiet and uniform and the good 

 agreement of the results indicates that the composition of the expired 

 air was uniform in all parts of the spirometer. 



In conclusion, it may be stated that the manipulation of the Tissot 

 apparatus is not difficult and that the results obtained with it are 

 reliable and entirely comparable with those obtained with other 

 respiration apparatus used for the determination of the respiratory 

 exchange in short periods. 



DOUGLAS METHOD. 



The method of collecting expired air in a rubber bag has been em- 

 ployed by a number of investigators. 1 Nearly every one of their 

 investigations has been severely criticized because a rubber receptacle 

 was used for collecting a mixture of gases containing an appreciable 

 amount of carbon dioxide. It is a well-known fact that rubber has a 

 tendency to absorb carbon dioxide and also to let it diffuse. Hufner 2 

 found that a much larger amount of carbon dioxide was absorbed than 

 of either oxygen or nitrogen. Kayser 3 found that 1 c.c. of rubber at 

 and 760 mm. absorbed 1.3507 c.c. of carbon dioxide. Graham 4 found 

 that carbon dioxide passed through a rubber membrane much more 

 rapidly than hydrogen or nitrogen. Atwater and Benedict, 5 on the 

 contrary, in using a rubber membrane in a sampling device found 

 that there was no diffusion of carbon dioxide with a percentage of 

 carbon dioxide in the air of not over 2 per cent, but there was an ab- 

 sorption and diffusion of water- vapor. 



Douglas 6 points out that care should be taken to obtain bags having 

 a negligible amount of diffusion and the bags used in this investigation 

 were both tested for this. A sample of air taken from the smaller 

 bag on July 6, 1912, at 9 h 45 m a. m., gave 4. 13 per cent of carbon diox- 

 ide; at 10 h 45 m a. m., 4.12 per cent; at ll h 45 m a. m., 4.09 per cent; 



'Regnard, Recherches experimentales sur les variations pathologiques des combustions respira- 

 toires, Paris, 1879, p. 286. Luciani, Das Hungern, Hamburg and Leipzig, 1890, p. 181. Marcet, 

 A contribution to the history of the respiration of man. London, 1897, p. 11. 



*Hufner, Wiedemann's Ann. d. Physik u. Chem., 1888, 34, p. 1. 



'Kayser, Ann. d. Physik u. Chem., 1891, N. F., 43, p. 548. 



4 Graham, Proc. Royal Society, London, 1866, 15, p. 223. 



'Atwater and Benedict, U. S. Dept. Agr., Office Expt. Stas. Bull. No. 136, 1903, p. 25. 



Douglas, Journ. Physiol., 1911. 42, Proc. Physiol. Soc., p. xvii. 



