8 



number of days required by the young to double their weight. 

 The amount of lime in himian milk, for instance, is one- 

 thirtieth of that in the rabbit's milk; while the time required 

 for the baby to double its weight is just thirty times greater 

 than that for the rabbit. 



Note that there are about equal amounts of lime and phos- 

 phoric acid in the milk of each, plenty of this material being 

 provided. 



In the next column we note the amount of protein in the 

 milk of these various animals. We find the relative propor- 

 tions are about the same as that of ash. The last column 

 shows the amount of sugar in the milk. This is in inverse 

 ratio to that of ash and protein, i.e., we find more sugar in 

 human milk and in the mare's milk than we do in that of 

 the ralibit or sow. About the only way we can explain this 

 difi^erence is the fact that the rapid-growing animals, or those 

 that double their weight in a very few days, need a large 

 amoimt of ash for the framework and also a large amount of 

 protein for building the tissues, whereas the sugar is needed 

 principally for heat and energy, and is not so essential to the 

 growth of the quick-growing animal as the other two, because 

 protein, in case of necessity, can also be used for heat and 

 energy. 



As the chick doubles its weight in about twelve days under 

 normal gTOwth, it would come somewhere between the young 

 rabbit and the pig. It therefore needs a large amount of ash 

 and protein in its food. 



It may seem to many unnecessary to dwell so long upon a 

 matter of this kind, but there are himdreds of people who give 

 their little chicks nothing but bread and cracked grain, or foods 

 containing no more ash than these. The following chart illus- 

 trates the comparative ability of poultry and ruminants to 

 digef^t some of our common grains: — 



