Development of Necessary Knowledge 191 



the still greater disadvantage of not learning by this 

 means why a particular combination of feeds has 

 superior qualities for causing growth or sustaining 

 milk secretion. The mere data showing that an ani- 

 mal ate so many pounds of food and produced so 

 many pounds of beef or milk are important business 

 facts, but they reveal nothing concerning the uses of 

 the several classes of nutrients and of themselves fur- 

 nish slight basis for developing a rational system of 

 feeding. We must somehow learn the function of pro- 

 tein, carbohydrates and fats in maintaining the various 

 classes of animals and the real effect of varying the 

 source, quantity and relative proportions of these nutri- 

 ents before we can draw safe general conclusions. 



CHEMICAL AND PHYSIOLOGICAL STUDIES 



As preliminary to more comprehensive and convinc- 

 ing methods of investigating feeding problems, there 

 has been going on during many years a necessarj^ study 

 of the compounds which are found in plants and ani- 

 mals. Much has been learned about the ultimate com- 

 position and the constitution of the albuminoids, carbo- 

 hydrates and fats, their physical and chemical proper- 

 ties, the compounds into which these bodies break 

 under certain conditions, the chemical changes to 

 which they are subject through certain agencies, and 

 their relation to one another. Investigations along 

 these lines have for j^ears occupied the time of some 

 of our ablest scientists, and, while such researches when 

 they were conducted may have seemed to the extreme 



