154 The Feeding of Animals 



of all the working parts of the animal's body. So 

 far, scientific research has not succeeded in demon- 

 strating that an albuminoid is ever synthesized (built 

 up from simple compounds) outside of the plant. It 

 appears that bodies of this class must come to animal 

 life fully elaborated. This is a truth of great sig- 

 nificance even in its relation to the nutrition of farm 

 animals. The nitrogenous tissues are those that largely 

 determine the vigor and quality of any animal, and as 

 these are formed rapidly in the early stages of growth, 

 a normal and unrestricted development demands an 

 abundant supply of proteid food. It is also true of 

 mature animals that sufficient protein is not only nec- 

 essary to health and vigor, but it is essential to pro- 

 duction that is satisfactory in quantity and quality. 



The functions of protein are not restricted, how- 

 ever, to the use already described. According to ex- 

 isting views, it is utilized in more ways than any 

 other class of nutrients. It was held at one time by 

 prominent scientists that outside the vegetable fats it 

 is the sole source of animal fats, and this view was, 

 not so very long ago, to some extent accepted. Indis- 

 putable proof to the contrary is now in our possession, 

 and some investigators even go so far as to deny the 

 possibility of the formation of fat from protein. On 

 this point, opinion is divided. Certainly we must be 

 convinced that nitrogen compounds of the food are, 

 with some species, not the most important source of 

 animal fat, for various investigators, such as Lawes 

 and Gilbert, Soxhlet, and others, have shown upon the 

 basis of searching experiments that sometimes over 



