MANUAL OF CATTLE-FEEDING. 185 



mals are to be regarded only as very probable, not as cer- 

 tain. 



In the first place, we do not know how much fat was 

 actually formed in these experiments. 



The estimates of its amount, based on the composition 

 of the increase of fattening animals as determined by 

 Lawes & Gilbert, are obviously very uncertain ; and even 

 in such experiments as those of Henneberg, Kern & "Wat- 

 tenberg, and of Weiske & Wildt, it is highly improbable 

 that the animals killed and analyzed at the beginning of 

 the experiments had exactly/ the composition of those re- 

 served to be fattened, and we have no means of judghig of 

 the amount of the difference. 



Again, in all cases we have assumed that 100 parts of 

 protein decomposed in the body gave rise to 51.4 parts 

 of fat. 



Now this number is a purely theoretical one, based on 

 a calculation by Henneberg of the greatest amount of fat 

 whieli could possibly be formed from a given weight of 

 protein; and, while there can be no doubt that fat is 

 formed from protein, it is very doubtful whether this 

 maximum amount is formed in every, or even in any, case. 

 It is a commonly observed fact that when a chemical com- 

 pound breaks up into simpler bodies, some of its latent 

 energy is set free, either as heat or in some other form. 

 Zuntz {loo, city p. 96) has, however, shown that such a 

 formation of fat and urea from protein as we have been 

 supposing, is only possible on the condition that the result- 

 ing products contain all the latent energy of the decom- 

 posed protein, and that none is given off in the decompo- 

 sition. This, Zuntz remarks, is a process wholly without 

 analogy in the animal body, where all decompositions are 

 accompanied by the setting free of considerable quantities 



