354 PHILOSOPHY OF ZOOLOGY. 



subject with great attention, was led from his experiments 

 to conclude, that moderate exercise increased the consump- 

 tion of oxygen, but if continued so as to induce fatigue, it 

 occasioned diminution. The exhilarating passions appear 

 likewise to increase the quantity, probably by exciting mus- 

 cular action. On the other hand, the depressing passions 

 and sleep, alcohol *, and tea, diminish the quantity. 



Dr PIIOUT likewise found, that the quantity of oxygen 

 consumed, is not uniformly the same during the twenty-four 

 hours; but is always greater at one and the same part of 

 the day than at any other. He determined, that its maxi- 

 mum occurs between 10. a. m. and %. p. m., or generally be- 

 tween 11. a. m. and 1. p. m., and that its minimum commen- 

 ces about 8 h 30' p. m., and continues nearly uniform till 

 about S h 30' a. m. He is inclined u to believe, that the 

 presence and absence of the sun alone regulate these varia- 

 tions." Here it may be observed, that in diurnal animals, 

 the forenoon, during which it appears that the consumption 

 of oxygen is at its maximum, is the period of activity or 

 muscular exertion ; while in the afternoon, in which the con- 



Dr PROUT found that " alcohol, in every state and in every quantity, 

 uniformly lessens, in a greater or less degree, the quantity of carbonic acid 

 elicited, according to the quantity and circumstances under which it is 

 taken.*' This result is certainly the reverse of what might have been ex- 

 pected, considering the temporary exhilarating effects of spirituous liquors. 

 That the quantity should be found diminished, after the exhilarating effects 

 of the alcohol had ceased, and the consequent depression had taken place 

 was precisely what might have been expected, and which the experiments of 

 Dr FIFE realize. " On the 8th of June, (says Dr FIFE) a much greater 

 quantity of wine than usual was taken, and the next day the quantity of 

 carbonic acid was repeatedly found as low as above stated, (5.75 per cent.) 

 On making the experiment again with less wine, the quantity of carbonic 

 acid was considerably reduced, though not so much as before," (only be- 

 tween 2 and 3 per cent.) ib, iv. 335. This diminished state certainly indi- 

 cates a previous excess. The apparent discordance of the results of these 

 experimenters probably arises from peculiarities of habit or constitution. 



