DIET OF THE COW. 555 



effect, and that the daily work of which an animal is capable 

 invariably falls short more or less of the estimate derived from 

 the consumption of the material whence the energy is derived. 

 Thus there is no difficulty in the supposition that the ox may 

 perform its day's work with less proportionate waste of flesh- 

 formers than the horse. 



Application of Theory to Feeding the Cow. The theory of 

 feeding the cow, as distinguished from that in accordance with 

 which the ox is fed, is to be drawn from the composition of the 

 milk, for the yielding of which the cow is kept. 



The composition of cows' milk, before the calf is allowed to 

 suck, is 



Caseine, . . .' . . 15.0 



Butter, ..... 2.6 

 Sugar, . . . . .3.6 



Ashes, ..... 0.3 

 Water, . . . . .78.5 



100.0 



What is remarkable in this analysis is, that the proportion of 

 caseine is very much greater than what is found in the milk of 

 dairy cows. Caseine is a proteine compound, one of the albu- 

 minoid proximate principles in short, a flesh-former. How 

 it comes to be so much more abundant in the first milk after 

 calving than at a subsequent period it is not very easy to 

 understand. During the period of pregnancy no caseine is 

 produced within the system of the mother, the demand of 

 material for the development of the calf being sufficiently 

 answered by such other proteine compounds as albumen and 

 fibrine. It is plain, however, that as soon as parturition takes 

 place, the extra demand for albumen and fibrine ceases, and 

 thus, as it may be supposed, these principles, in so far as they 

 are not necessary for the maintenance of the cow itself, become 

 changed to the caseine of the milk. Chemists believe that 



