HANUAL OF CATTLE-FEEDIITG. 01 



ft)rce exerted bj the body. Tliis does not appear to be 

 fully establislied, but even if we do not bold tliis view, 

 we sbali see, in a subsequent ebaptei*, that tbere is strong 

 reason to believe tbat non-nitrogenons substances play an 

 important part in tbe preparation of tlie muscles for tlie 

 exertion of force, and that a constant supply of tliem in 

 tlie blood is an important condition of Lealthy activity. 

 On tbe otlier band, it lias been sliown tbat a large quantity 

 of sugar in tbe blood is very burtful. 



Tbe office of tbe liver seems to be to arrest the sugar on 

 its way from tbe portal capillaries and, by converting it 

 into glycogen, to prevent an injurious accumulation of it 

 in tbe blood, wbile tbe glycogen, by its gradual re-conver- 

 sion into sugar, yields a continual supply of tbis substance. 



G-lyeogen may "be formed from Protein. — ^If a sup- 

 ply of sugar to tbe blood is important or necessary, we 

 sbould expect to find some provision for it in tbose animals 

 \v^bich take none in their food — ^. ^., the carnmora. 



This is, in fact, the case. The liver has the power to 

 form glycogen from albuminoids, as is shown by the fact 

 that that su]>stance is formed in animals fed entirely on 

 albuminoids. This l>eing so, there is no evident reason 

 why the same formation of glycogen from protein may 

 not take place in all animals. Indeed some authorities 

 hold that it does, and that all the albuminoids destroyed 

 in the body are first decomposed in the liver into glycogen, 

 and urea and similar products. 



It win be shown in a subsequent chapter, however, tbat 

 under some circumstances fat may be formed from the 

 protein of the food and stored up in the body, and Yoit 

 and his followers hold that the iirst decomposition of pro- 

 tein in the body yields fat and not glycogen. However 

 this may be, it is certain that a jjart of the protein may 



