50 Milk and Its Products 
It goes without saying that a ration cannot be of 
the highest degree of effectiveness if it is not pala- 
table, if the animal does not eat it, not only readily 
but eagerly.. The factors of palatability are not well 
understood, nor always easily recognized, and our 
knowledge of them is to a very considerable extent 
empirical, and the result of actual observation and 
experience. About all that can be said in this respect 
is that of two rations or combinations of food similar 
in all other respects, that one will be most effective 
that is most readily eaten by the animal. There are 
certain adventitious aids to palatability, such as salt, 
water or succulence, and freshness. The peculiar char- 
acteristics of certain plants also make them .particu- 
larly palatable or unpalatable for certain animals, or 
classes of animals, and in addition there are various 
vegetable aromatics and semi-tonics, and certain inor- 
ganic salts, that are recognized as having a marked 
effect upon the appetite. A continuous use of these 
latter for healthy animals seldom results in distinct 
advantage. The secretion of milk seems to be inti- 
mately connected with the water content of the food. 
Milk itself is a watery substance (ordinarily about 
seven-eighths water), and of course the water, which 
makes up so large a part of it, demands a corres- 
ponding consumption of water by the animal. It 
seems almost necessary that a certain part of this 
waiter should be regularly incorporated with the food 
or, in other words, it is of great advantage for the 
secretion of milk that at least a part of the food 
‘should be composed of materials containing large 
