RESPIRATION 39 



ent organisms will evidently affect the ratio between oxygen 

 absorbed and carbon-dioxide given off. The ratio will be 

 changed either by the greater absorption of oxygen for the 

 oxidation of organic acids or by the smaller amount of 

 carbon-dioxide produced when such incompletely oxidized 

 by-products as alcohol are formed. Finally, every factor in 

 the environment of the organism, its food, the influence of 

 its neighbors, the weather, etc., will affect the ratio more or 

 less by affecting the organism itself. 



For the reasons made clear in the foregoing pages, the 

 amount of carbon-dioxide exhaled is by no means an ac- 

 curate index of the rate of respiration and of the amount 

 of energy liberated, but taking this substance only, we may 

 still make some interesting comparisons. For instance * 

 nan exhales in 24 hours CO 2 , equal to 1.2% of his body- 



eight; moulds exhale in 24 hours CO 2 , equal to 6.0% of 

 their body- weight ; active bacteria exhale in 24 hours CO., 

 equal to 200.0% of their body- weight. Organisms which, 

 like man, have comparatively feeble respiratory power, 

 must either, as he does, supply themselves with energy by 

 external means or limit their activities to what they can 

 themselves produce. ~lvjng birds produce much larger 

 amounts of carbon-dioxide and hence of energy than man, 

 and upon the latter depends their abilit}^ to fly. The very 

 important part taken by the moulds and bacteria in 

 Nature is accounted for by their being able to supply 

 themselves with such tremendous amounts of energy. 



SUMMARY 



Respiration, controlled and accomplished by living organ- 

 isms, produces disturbances of equilibrium in the living 

 substances of the organism ; these disturbances give im- 

 pulses to further molecular and atomic movements and to 

 further vital acti vit ies-rrespir ation traqffif flTin latent (po- 

 tential) to active (kinetic) energy, and reduces the amounts 

 of carbohydrates and fats, to a less degree also proto- 

 plasmic substances, in the body. 



* Pfeffer. Pflanzenphysiologie, Bd. I., p. 526. Engl. transl.,vol. I., p. 522. 



