39 



THE POPULAR SCIENCE MONTHLY. 



grain, consumed from twenty-six to thirty pounds of dry substance 

 per week, for each hundred pounds of live weight, and yielded one 

 pound of increase in weight for each four or five pounds of dry sub- 

 stance in their food. Oxen, therefore, consume more dry substance of 

 food, in proportion to their weight, than sheep, and sheep consume 

 more than pigs, while, in return for feed consumed, pigs yield more 

 than sheep, and sheep gave better results than oxen. It must be re- 

 membered in this connection, as has already been pointed out, that the 

 food of oxen contained more woody fiber, while that of the pigs was 

 comparatively concentrated and digestible, and therefore of better 

 quality. With sheep of different breeds it was found that, under the 

 same conditions as to age and fatness, the food consumed was in pro- 

 portion to their live weight. The relative value of the larger and 

 smaller breeds seems, therefore, to depend, to a great extent at least, 

 upon their habits and hardiness, and their adaptation to the conditions 

 of the locality in which they are placed. 



In studying these experiments, it will be well to keep in mind the 

 twofold function of food in the animal economy : first, as the source 

 of energy for the performance of work in the various organs of the 

 body, which is required in elaborating the peculiar animal products 

 sought in the process of feeding (as milk, flesh, wool, etc.), and in car- 

 rying on the processes of repair and reconstruction to maintain the in- 

 tegrity of the animal machinery ; and, in the second place, as supplying 

 the materials for the construction or elaboration of the special animal 

 products. The popular notions of nutrition assume that this supply 

 of materials in the food for the new product sought is the most impor- 

 tant, and the supply of energy for the performance of work is over- 

 looked or assigned a subordinate position. 



The results of the experiments relating to the use and ultimate dis- 

 position of the food consumed by animals when fattened under average 

 conditions, as to feed and increase, are given in the following table : 



The figures in the last column of the table are not intended to rep- 

 resent all of the internal work of the system. They simply show the 

 amount of non-nitrogenous constituents that are not accounted for in 

 the stored-up increase, or in the manure, and thus are properly desig- 

 nated as having been used in internal work. From an agricultural 

 etand-point, the proportions of food-constituents stored up as increase, 



