CHEMICAL DYNAMICS OF ANIMAL NUTRITION 163 



therefore, a mechanism which tends to prevent excessive acidity or 

 alkalinity of the liver ; in the presence of acid nitrogenous degradation 

 products are formed, from which ammonia is produced in the digestive 

 tract ; it is possible also that the presence of alkali stimulates the pro- 

 duction of the non-nitrogenous acid bodies. Further research is needed 

 on this point. 



The production of nitrogenous degradation products proceeds also 

 at such a rate that there is never a dearth of nitrogenous bodies in the 

 blood stream, and the bioplasm of the tissues, especially the mucous 

 membrane of the small intestine, can remain saturated with side chains, 

 for we have seen that the liver of a fasting animal contains more residual 

 nitrogen than does that of a well-fed animal. 



From these researches, it follows, that while the animal derives 

 most of its energy from the oxidation of carbohydrates, and rapidly 

 eliminates nitrogen from albumens, the latter, for all that, play an 

 important role in nutrition, for the degradation products are needed, 

 not only to satisfy, as Folin has suggested, the needs of endogenous 

 metabolism of the organism representing the wear and tear of the 

 tissues, but also to supply sufficient ammonia to maintain a certain 

 amount of general intracellular alkalinity. In the absence of this 

 amount, nitrogenous equilibrium ceases to be maintained. 



It remains, lastly, to consider the bearing of these conclusions in 

 certain abnormal cases, resulting in what Speck has called tissue 

 metabolism (NahrungstofFwechsel as contrasted with Kraftstoffwechsel). 



Four instances are cited by Speck, in which tissue degradation 

 sets in, viz. : (i) lack of oxygen ; (ii) poisoning with phosphorus, 

 arsenic, etc. ; (iii) withdrawal of water ; (iv) in fever. 



The factors regulating the animal heat of the body are too little 

 known to render it profitable to discuss the course of metabolism in 

 fever ; whether high temperature is due to increased oxidation or not, 

 is doubtful, as the results obtained by the investigation of the 

 respiratory quotients are open to doubt. Little is known also of the 

 course of metabolism in the absence of water. 



The metabolism with lack of oxygen, and in phosphorus poison- 

 ing, have formed the subject of numerous researches, and several facts 



