7 oo CHEMISTR Y OF RESPIRA 1*1 ON. 



animal was placed ; this air was analysed for carbon dioxide, and the oxygen 

 absorbed by the animal was replaced by a corresponding amount supplied from 

 a gasometer. 



The consumption of oxygen by animals living in water can be determined 

 by titrating a sample of the water before and after the confinement of the 

 animal in a known volume of water. Quinquand 1 used for this purpose 

 sodium hyposulphite, according to Schiitzenberger's method. 



The conditions which affect the respiratory exchange. A de- 

 termination of the respiratory exchange not only gives the absolute 

 value of the oxygen absorbed, and of the carbon dioxide and water ex- 

 creted, but also shows the relationship between the intake of oxygen 

 and the output of carbon dioxide. This ratio between the volume of 

 oxygen absorbed and the volume of carbon dioxide discharged is known as 



CO 

 the respiratory quotient -~, and indicates how much of the oxygen coin- 



^2 



bines with carbon to form carbon dioxide, for one volume of oxygen in 

 combining with carbon yields one volume of carbon dioxide. Various 

 conditions influence both the amount of the respiratory exchange and 

 the relative proportions of the gases, but it must be remembered that 

 determinations of short duration may give rise to erroneous conclusions, 

 for oxygen may be stored up for some- time within the body, and 

 carbon dioxide may still be formed and discharged when there is no 

 intake of oxygen. 



The question here arises, Does nitrogen play any active part in 

 respiration, is there any absorption or discharge of nitrogen ? 2 The 

 older observers found that nitrogen was sometimes absorbed by the 

 lungs, and in nearly all of Eegnault and Eeiset's 3 determinations of the 

 respiratory exchange in different animals there is an alteration in the 

 amount of nitrogen present in the air, denoting generally a discharge of 

 a small quantity of nitrogen from the animal. Marchancl 4 had also ob- 

 tained similar results ; he found in ten experiments upon guinea-pigs 

 that the average discharge of nitrogen was equal to 0'94 per cent, of the 

 output of carbon dioxide, and in three experiments 011 pigeons to 0'85 

 per cent. Seegen and Nowak 5 also found a discharge of nitrogen, 

 varying from 4 to 9 mgrms. per kilo, and hour in thirty- two experiments 

 upon rabbits, dogs, and hens. 



This discharge of nitrogen in many cases appears to be due to an 

 error of experiment. 6 Analyses, purposely made by Colasanti 7 to test 

 this point, showed no discharge or absorption of nitrogen by guinea-pigs. 

 The small amount observed by other experimenters may be due either 

 to nitrogen discharged from the alimentary canal or to experimental 

 errors. According to Jolyet, Bergonie, and Sigalas, 8 an amount of 

 nitrogen varying from ^ to -j-^nr f the oxygen absorbed is taken 

 up by the blood in its passage through the lungs of a man or a clog. 

 In any case the amount of nitrogen absorbed or discharged under 



1 Compt. rend. Acad. d. sc., Paris, 1873, tome Ixxvi. p. 1141. 



2 For further details, see Voit, Hermann's "Handbuch," Bd. vi., Th. 1, S. 37. 



3 Ann. de chim. et phys, Paris, 1849, Se"r. 3, tome xxvi. 



4 Journ. f. praJct. Chem., Leipzig, 1848, Bd. xliv. S. 1. 



5 Sitzwngsb. d. k. Akad. d. Wissensch. Math.-naturw. Cl., Wien, 1875, Bd. Ixxi. (3), 

 S. 329 ; Arch.f. d. ges. PhysioL. Bonn, 1879, Bd. xix. S. 347. 



6 Pettenkofer and Voit, Ztschr. f. BioL, Miinchen, 1880, Bd. xvi. S. 508. 

 ''Arch.f. d. qes. PhysioL, Bonn, 1877, Bd. xiv. S. 92. 

 8 Compt. rend. Acad. d. sc., Paris, 1887, tome cv. p. 675. 



