534 PHYSIOLOGY AT THE FARM. 



Mineral Matters. A similar difficulty arises with respect 

 to the mineral matters. It is not possible that a horse, even 

 under the severest labour, can require so much mineral matter 

 for the repair of the tissues as is contained in the food, for 

 example, of the working diet namely, 19.39 oz. Much of 

 this the horse certainly does not require, yet it is not practi- 

 cable to give enough of the requisite heat and fat givers and 

 flesh-formers without this superfluity of mineral matters, for 

 the simple reason that the articles of food within our reach do 

 contain more than enough of such mineral materials. The 

 illustration commonly chosen by physiologists on this point, 

 in the case of herbivorous animals, is potash, which abounds 

 in all vegetable food, and yet hardly enters into the composi- 

 tion of the animal solids or fluids, so that there seems to be a 

 necessity for its being thrown out from the animal system 

 simply as a foreign body. It is true that in the human body 

 soda is the alkali of the blood and of the solids ; but as the 

 alkalinity of the blood in herbivorous animals depends on the 

 presence of alkaline carbonates, it is possible that the potash 

 of their food may be necessary to render their blood alkaline, 

 before it is separated from the system by the urine. Thus, 

 though potash constitutes no part of the muscular tissue, the 

 waste of which under bodily exertion chiefly takes place, it 

 would be unsafe, without further inquiry, to give food for the 

 repair of waste in such animals that did not contain potash. 

 The proportion of potash in the ashes of meadow-hay is 21.7 

 per cent ; in the ashes of oats, 9.6 per cent ; in the ashes of 

 beans, 23 per cent : the entire ashes in meadow-hay being 

 10.03 per cent ; in oats, 2.59 per cent ; in beans, 3.10 per cent. 



The most important of the mineral matters with reference 

 to the choice of food is phosphoric acid. From 45 to 47 per 

 cent of phosphoric acid has been found in the ash of horse- 

 flesh, and here it is said to be chiefly combined with potash, 



