INFLUENCE OF FOOD. 361 



the head of " Nutrition," must not be suffered to pass without 

 some notice in the present place. If, for instance, we consider the 

 ratio of the absorbed oxygen to the oxygen which is again separated 

 (with the carbonic acid), we perceive that it essentially depends 

 upon the quality of the food ; but yet after the abundant use of 

 carbo-hydrates the ratio calculated from the above considerations, 

 will never correspond with that which is found by direct experi- 

 ment : thus, for instance, if we feed an animal on pure starch, we 

 shall never obtain the required ratio of 100 : 100, that is to say, 

 the whole of the oxygen absorbed will never be contained in the 

 expired carbonic acid, because a fraction of it will be expended in 

 the formation of water, for the simple reason that this ratio does not 

 depend solely upon the food, but is modified by the combustion of 

 the nitrogenous organic parts which are destroyed during vital 

 activity. During life those nitrogenous substrata which have been 

 subservient to the functions of the organism, are continually be- 

 coming effete and unfitted for further use, and finally reduced to a 

 state of oxidation, for the purpose of being eliminated; these 

 bodies consume a portion of the oxygen in the oxidation of their 

 hydrogen, and, consequently, this portion of the absorbed oxygen 

 is not exhaled as carbonic acid, and the ratio of the absorbed 

 oxygen to the exhaled carbonic acid differs, therefore, from that 

 which we might assume from the composition of the carbo-hydrate. 

 We have thus merely to inquire how much nitrogenous matter is 

 destroyed during the normal course of the vital movements, and 

 what fraction of the absorbed oxygen is consumed by it. To find 

 the amount of this coefficient for every organism, constitutes a 

 problem in the physiology of nutrition. We should, therefore, 

 acquaint ourselves with the typical consumption of the organic con- 

 stituents in order to find the proportion which essentially expresses 

 the respiratory process, or this respiratory function. If, however, 

 we knew the typical amount of the daily loss of tissue, we might 

 very readily calculate from the quantity of the consumed starch, 

 the relation existing between absorbed and exhaled oxygen. The 

 loss of tissue, consisting of albuminates and collagen yields, as we 

 find from experiments on inanition, the ratio of 100 : 83 '6 ; if now 

 we express the magnitude of the typical consumption of nitroge- 

 nous matter by c, and the quantity of the consumed starch by , 

 the proportional number for the excretion of carbonic acid might 



very easily be deduced from the formula - c ' The expe- 



riments made on fasting animals warrant the conclusion, that the 



