872 COMPOSITION OF EXPIRED ALVEOLAR AIR. 



(2) The ehang'e in concentration is independent of the depth of 

 respiration, bnt depends on the speed with which the air is 

 expired. The more slowly the air is breathed ont, the o-reater the 

 chang-e in concentration of the gases of the final portion. 



(;]) Tliese results lead to the inference, that the alveolar air in 

 tlie pulmonary atria at the end of an expiration contains a lower 

 concentration of oxyg-en and a higher concentration of carbou 

 dioxide, than the air last expelled from the month in the rapid 

 expiration. 



I beg to express my indebtedness to Professor Sir Thomas 

 Anderson Stuart, in whose De]iartment this researcli has l)een con- 

 ducted, and to thank Dr. H. G. Chapman for his encouragement 

 and assistance in this work. 



REFERENCES. 



1. Ethel C. Ptnkf.rtox — Proc. Linn. Soc. X. S. Wales. 1017, xlii., 



p. 146. 



2. Henderson. Y., CHiLLiNnwoRTH, E. V.. and Whitney, J. L. — 



Amer. Journ. Phys.. xxxviii.. p. 1, 1915. 

 ?). Haldane. J. S. — Amer. Jcmrn. Pliys.. xxxviii.. p. 20, 1915. 

 4. Krooh, a., and Lindhard, J. — J<mrn. Phys.. xlvii., p. 30, 1913 ; 



p. 430, 1914. 



Addendum. — Seven sets of analyses with Haldane's apparatus 

 were made on the contents of the brass tube after washing it out 

 with gaseous mixtures containing known amounts of carbon 

 dioxide. The results demonstrated the completeness of the 

 replacement. 



