THE INFLUENCE OF CHEMICAL FACTORS 71 



The effect was most pronounced on the oxygen intake, while the 

 CO 2 output was much less affected. 1 Tangl's experiments were per- 

 formed on animals whose kidneys had been removed and the work of 

 excreting the NaCl cannot therefore be responsible for the increase in 

 metabolism. 



The investigation of the influence of NaCl was continued by Verzar 

 [1911] who found that a similar though slightly greater increase was 

 produced also in curarized dogs with intact kidneys and further that 

 even I per cent, or 0*75 per cent, solutions of NaCl produced a distinct 

 increase in metabolism. 



Raeder [1915], who worked on urethanized rabbits and whose 

 technique is in several respects an improvement upon Verzar's, con- 

 firmed these results to a certain extent, but the increases in metabolism 

 observed by him were smaller and may, in his opinion, be due simply to 

 the increased functional activity of the heart and kidneys. 



Lusk and Riche [1912, i] found that ingestion of saline solutions 

 (150 c.c. of 4 per cent.) had no influence upon the metabolism of the 

 resting dog. 



Plydrogen ion concentration. Alterations in the hydrogen ion con- 

 centration of the organism are possibly responsible for the effects 

 observed in mammals of injections or feeding with alkalis and acids. 

 The inference is by no means certain, however, as it appears doubtful 

 whether the hydrogen ion concentration of the blood or tissues has 

 been at all changed in the experiments in question. 



Lehmann[i884] found that alkali produced a slight increase (5 per 

 cent.) and acid a slight fall (5 per cent.) in the metabolism of curarized 

 rabbits. His results have been confirmed by Chwostek [1893] as 

 regards acids and by Loewy [1888, 1903] as regards alkalis. Loewy 

 found that the metabolism of a dog rose 30 per cent, by feeding it for 

 twelve days with 3 gr. of sodium carbonate per day. On man a dose 

 of 5 gr. of sodium carbonate per day was without effect. Raeder 

 found that injections of small doses of acids or alkalis were either 

 without effect or caused a slight increase in the metabolism cor- 

 responding to increased functional activity of the heart or kidneys, 

 while larger, toxic, doses invariably produced a decrease in the meta- 

 bolism. This last effect was observed also by Leimdorfer [1914]. 



Amino acids. Graham Lusk [191 2, 2] has found that comparatively 



1 In several of the papers here under review rather far-reaching conclusions are drawn 

 from changes observed in the respiratory quotients. As pointed out above (p. 16) these 

 must be regarded with suspicion. 



