93 MANUAL OF OATTLE-FEEDUNTG. 



be used in fat formation, and as certain tliat part of it may 

 also be used by the liver as a source of glycogen. 



Protein as the Sole Source of Glycogen. — The views 

 of the glycogenic function of the liver just stated, tliougli 

 widely accepted, ai^e not undisputed. Many good autlioii- 

 ties hold that under all circumstances protein is the source 

 whence glycogen is formed. According to this view, the 

 carbhydrates of the food are oxidized in place of the non- 

 nitrogenous products of the decomposition of protein, and 

 protect the latter, so that they are, in part at least, de- 

 posited in the liver in the form of glycogen, to be drawn 

 on when the supply of carbhydrates in the food is insuffi- 

 cient. 



That is, the liver has the power of preparing carbhy- 

 drate material fiom protein and storing it up in an insol- 

 uble form until such time as it is needed. 



Which of these two theories is true, or whether tlie 

 truth lies between the two, is as yet undecided, nor is a 

 discussion of the comparative probability of the two views 

 in place here. 



Oxidations in the Body are Gradual. — In the fore- 

 going paragraphs we have, for the sake of simplicity, 

 spoken as if the processes of decomposition and oividation 

 were very simple and immediate — as if sugar were burned 

 directly to carbonic acid and water, protein split up at once 

 into fat and urea, etc. This is far from being the case. 

 While the final result is as if the oxidations took place in 

 the way spoken of, and while we are therefore justified in 

 60 speaking when we look at the chemical changes in the 

 body as a whole, it must always be with the understanding 

 that the changes which actually take place are very nu- 

 merous and compHcated, and tha,t both their nature and 

 location are largely hidden from us. The simple fact that 



