CHAPTER III. 



THE EXCHANGE OF NITROGEN, HYDROGEN, METHANE, AMMONIA AND 

 OTHER GASES OF MINOR IMPORTANCE. 



NITROGEN. 



WHILE Lavoisier and Seguin [1814] arrived at the conclusion that 

 the atmospheric nitrogen was neither absorbed nor excreted by the 

 body, Regnault and Reiset [1849] observed in most of their careful 

 quantitative experiments on healthy animals a slight but very variable 

 exhalation of free nitrogen, and on animals suffering from inanition 

 or other causes usually a slight absorption. On normal dogs they 

 found on an average a production of 4-6 2-15 c.c. nitrogen per 

 litre of oxygen absorbed. 1 Seegen and Nowak [1879] found con- 

 stantly exhalation of nitrogen and their results were very regular : 

 normal dogs 5-5 0-17 c.c. nitrogen per litre of oxygen. 1 These 

 results were considered untrustworthy because the experiments of 

 Voit, Gruber and others on the nitrogen balance did not show any 

 deficit to correspond to the free nitrogen found by Seegen and 

 Nowak or by Regnault and Reiset. An attempt by Leo [1881] to 

 settle the problem iwas inconclusive because the technique was faulty, 

 and the question was allowed to remain undecided for a long time. 

 Oppenheimer [1907] found in a series of experiments on dogs that 

 there was almost constantly an absorption of nitrogen (eleven cases 

 out of thirteen) amounting on an average to 2'O 075 c.c. per litre 

 of oxygen, 1 but he had no doubt in ascribing the result to experi- 

 mental errors, and concluded therefore that the gaseous nitrogen did 

 not take any part in the respiratory exchange. About the same time 

 Krogh [1906] working with chrysalides of butterflies, eggs under in- 

 cubation, and mice, measured excretions of nitrogen amounting to 

 O'39 0*15 c.c., 0*4 c.c. and O'H 0-07 c.c. nitrogen respectively per 

 litre of oxygen, and concluded that these insignificant excretions were 

 probably real in so far as they could be ascribed, in the case of the 



1 Averages calculated by Krogh [1908]. 

 52 



