MANUAL OF CATTLE-FEEBING. 341 



a kind of fermentation. Little is known of this process, 

 but it is not improbable tliat the small quantities of marsh- 

 gas and hydrogen exhaled bj ruminants have their source 

 in it, and this fact indicates that a considerable part of the 

 latent energy of the cellulose is liberated during its diges- 

 tion. 



This raises the question whether the various carbhy- 

 drates are equally valuable as nutrients — a question which 

 has, as yet, received scarcely any attention. Their equiva- 

 lency has been assumed and made the basis of the calculation 

 of rations, simply because, in the lack of all evidence, this 

 was the only practicable method. It is quite probable that 

 this assumption does not involve any very great error, 

 except, perhaps, in the case of celhilose ; but the actual 

 comparative value of these substances can be determined 

 only when we know, Jirstj how much latent energy each 

 contains, and, second^ how much of this energy is liberated 

 during digestion. 



This is, of course, equally true of the other classes of 

 nutrients ; * but tlie study of this subject can hardly be 

 said to have begun, and the only object' of mentioning it 

 here is to show how provisional are our present methods 

 of estimating the value of fodders, and to guard the reader 

 against the error of considering thefn final- and conclusive. 

 They are of grea»t value and have rendered Yerj important 

 service ; it is certain that they are not grossly erroneous. 

 At the same time, no good and much harm may come 

 from an unintelligent overestimate of their accuracy and 

 value. 



The so-called synthetic chemical actions (that is, forma- 



* The few results wMch have been obtained on the albuminoids will 

 be mentioned in another connection. They indicate that the vegetable 

 and animal albummoids are practically equivalent. 

 11 



