724 Starch Equivalents of Feeding Stuffs. [dec. 



mastication and digestion of the wheat straw throws so much 

 work upon the functions of the body that after deducting the 

 amount of energy used up in making the nutrients into a 

 form that can be assimilated, very little is left to be placed to 

 the credit of the animal body. Mastication and digestion are, 

 as it were, a first charge upon the digested food material, 

 and when this has been met the balance can be used for other 

 purposes by the organism. 



Experiments which have been designed to throw light upon 

 this subject, and which have been carried out with exemplary 

 care, have shown that the digested nutrients (protein, fat. 

 carbohydrates, &c.) in such a food as linseed cake can be 

 regarded as capable of producing the effect which would be 

 obtained if they had been fed in pure form. When a full- 

 grown animal is chosen, as is generally done in experiments 

 of this nature, it is possible to determine directly by increase 

 in body weight what gain has been caused by the feeding 

 of certain of these nutrients, for it is well known that such 

 an animal utilises the excess of food which its gets beyond 

 its maintenance requirements for the formation of fat; the 

 body is not capable of increasing in flesh to any appreciable 

 extent. When, on the other hand, the digestible nutrients 

 in a coarse fodder are considered it has been shown that the 

 theoretical quantity of fat is never formed. The reason for the 

 difference in these two cases undoubtedly lies in the fact that 

 a material easy of mastication and digestion, like linseed 

 cake, does not require much expenditure of energy for these 

 processes, and there is on that account a large amount of 

 nutritive matter left over for the formation of fat, when the 

 ration is a productive one, i.e., when there is more food 

 material than the animal requires for maintenance purposes. 

 On the other hand, a coarse fodder, like straw, requires a larger 

 expenditure of energy for the conversion of the feeding mate- 

 rial into a state fit for assimilation, and so a correspondingly 

 smaller balance is retained for the building up of body tissue 

 (chiefly fat). 



To avoid any misunderstanding, it may be explained that 

 every animal requires a certain amount of food for mainten- 

 ance; that is, for making good the losses which occur un- 

 ceasingly in every animal body. The movements of the 



