600 A MIXED FOOD NECKS3ARY TO ANIMALS. 



bably be found to thrive better on the mixture than if fed upon any one 

 of these kinds of food alone. 



2°. Quantity of fixed saline matter and of earthy phosphates which 

 the food ought to contain. — A fidl growi] animal rejects in its dung, its 

 urine, and its perspiration, as much saline and eaithy matter as its 

 food contains. If its body is merely maintained in its existing condition, 

 only that which is removed from it by the daily waste is restored to it by 

 the daily food. Thus whatever quantity of saline and earthy matter is 

 present in the food, an equal quantity is found in the excretions of the 

 living animal. 



But how much of that which is found in the excretions has actually 

 formed part of the living body, and been removed from it in consequence 

 of the natural waste ? This we have no means as yet of determining. 

 It must be considerable, but it varies with many circumstances, and the 

 experiments which have hitherto ^been made and published do not enable 

 us to say how much the average waste really is, and how much of the 

 several more common kinds of food ought to be consumed by a full 

 grown animal, in order to supply it w4th the necessary daily proportion 

 of sahne and eartliy substances. 



The benefits so often derived from the use of salt in the feeding of 

 stock show liow a judicious admixture of saline matter with the food 

 may render its other constituents more available than they would other- 

 wise be, to the support and increase of the animal body. 



§ 7. The health of the animal can he sustained only hy a mixed food. 



From what I have already stated, you see that the vegetable food eaten 

 by a full grown animal for the purpose of keeping up its condition should 

 contain — 



1°. Starch or sugar, to supply the carbon given off' in respiration. 



2*^. Fat or fatty oil, to supply the fatty matter which exists more or 

 less abundantly in the bodies of all animals. 



3°. Gluten or fibrin, to make up for the natural waste of the muscles 

 and cartilage. 



4°. Earthy phosphates, to supply what is removed from the bones of 

 the full grown animal by the daily waste ; and — 



5°. Saline substances — sulphates and chlorides — to replace what is 

 daily rejected in the excretions. 



Hence the food upon which any animal can be fed with the hope of 

 maintaining it in a healthy state 7nust be a mixed food. Starch, or sugar 

 alone, or pure fibrin or gelatine alone, will not sustain tlie animal body, 

 because these substances do not contain what is necessary to build up all 

 its parts, or to supply what is daily given off' during respiration and in 

 the excretions. The skilful feeder, therefore, will not attempt to main- 

 tain his stock on any kind of food which does not contain a sufficient 

 supply of every one of the kinds of matter which the body requires. 



Two other points he will also attend to. First, he will occasionally 

 change the kind of food, or will vary the proportions in which he gives 

 the ditferent kinds of fodder to his feeding stock. This practice is founded 

 on the fact that, although every crop he raises contains a certain propor- 

 tion of all the substances v lich the animal requires, yet some contain 

 one of these in larger qua itity than others do, and by an occasional 



