Food Requirements of Animals. 253 



differences in the skeleton development. In this experiment the 

 proteins were abundantly supplied in both rations, but only in the 

 second was there a liberal supply of lime and phosphoric acid. 

 Where such a supply was maintained the skeletons were large 

 and strong. 



Jordan fed two lots of steers from calf -hood on rations widely 

 different in their nutritive ratio. The one lot received for grain, 

 oil meal, wheat bran and corn meal, and the other lot corn meal, 

 with a minimum proportion of wheat bran. A nutritive ratio of 

 1 :5.2 and 1 :9.7 was maintained. At the end of 17 months and 

 27 months, one animal from each lot was killed and the entire 

 body, exclusive of hide, analyzed. There was no material differ- 

 ence in the composition of the animals. ' ' The amount of growth 

 was at first more rapid with the more nitrogenous ration, but the 

 kind of growth appeared to have been controlled by the somewhat 

 fixed constitutional habits of the breed. " (Jordan.) 



It is sometimes claimed by practical men that feeds rich in bone- 

 forming materials should be withheld from the pregnant mother ; 

 that such feeds are conducive to large boned offspring, making it 

 difficult for the young to be born. Little data on this question 

 are available, but from some experiments on swine at the Wis- 

 consin Station, there is no evidence that excessive supplies of bone- 

 forming materials influence the size or the ash content of the 

 skeleton of the newly born. It appears that the power to main- 

 tain a constant composition for the foetus, independent of wide 

 variations in food supply, lies inherent in the mother. 



The adult animal and food for maintenance. The food of an 

 adult animal, neither gaining nor losing in weight, is used for 

 renewal of waste tissue, the growth of hair, horn and wool, and 

 for the production of heat and mechanical work. The work per- 

 formed consists in the muscular movements involved in chewing 

 and moving the food along the intestinal tract; muscular move- 

 ments of the heart in pumping the blood; respiration and the 

 metabolic activity of the cells in causing the chemical transforma- 

 tions of the nutrients. This is internal work. It has been cal- 



