IN THE BODY OF A FDLL-GROWN ANIMAL. 509 



30 ounces of wheaten flour ; or 



45 " of wheaten brend ; or 



14 " of fresh beef or mutton ; or 



12 " of pease or bean meal ; or 

 4 " of cheese ;* 

 Or, if we live wholly upon potatoes or rnilk, we must eat no less than 

 six cr seven pounds of the former daily, or drink three or four imperial 

 pints of the latter — if we would restore to the body as much of the sub- 

 stance of its muscles and cartilage as is daily removed from it by the 

 urine. 



But the urine is not the only channel through which nitrogen is given 

 ofT from the animal body. A considerable, though, of course, a variable 

 proportion is found in the solid excretions or dung, which has also been 

 derived from the substance of the body itself. A small quantity of ni- 

 trogen is believed to be given otf from the lungs also in breathing, and 

 from the skin in the perspiration, which nitrogen must have been either 

 directly or indirectly derived from the food. And, lastly, of the fibrin or 

 other food containing nitrogen which may be introduced into the stomach, 

 a portion must pass the mouths of the absorbent vessels as it descends 

 through the intestines and thus escape with the dung, without having 

 performed its part in the ordinary nourishment of the body. 



It is impossible to maice any correct estimate of the amount of nitrogen 

 which escapes from the animal in the several ways just noticed — in the 

 solid excretions from the lungs and from the skin — or of the quantity of 

 food which is necessary to supply its jjlace. If we suppose the loss 

 through all these sources taken togetlier to be equal to one-half or two- 

 thirds of that which is found in the urine, then the whole quantity of dry 

 fibrin which the f(X)d ought to contain would amount to four and a half or 

 five ounces in the day. To supply this, we must eat of bread, beef, 

 cheese, potatoes, or milk, one half more than the quantities already 

 specified. 



No experiments have hitherto oeen published from which we can de- 

 termine the average quantity of nitrogen rejected in the excretions of the 

 horse, the cow, or the sheep, and, consequently, the amount of waste 

 which takes place in ordinary circumstances in the muscles and cartilage 

 of these animals. If we suppose that in the horse or cow it is in direct 

 proportion to their weights, compared with that of a full grown man — or 

 five times greater than in a man — then the loss of dry fibrin would 

 amount to 20 or 25 ounces in the 24 hours. To supply this, the animal 

 must eat the following quantities of one or other of tlie kinds of food here 

 mentioned : — 



120 lbs. of turnips. 17 lbs. of clover hay. 



115 ♦' of wheat straw. 12 " of pea straw. 



75 •' of carrots. 12 " of barley. 



67 " of potatoes. 10 " of oats. 



20 " of meadow hay. 5 " of beans, f 



Or instead of the whole quantity of any one of these, a half or quarter or 

 any other proportion of each may be taken, and the animal will pro- 



* 8upposine the wheaten flour to contain 10 per cent, of gluten, and the cheese one half 

 ks weight of dry curd (see also pp. 506 and 531.) 

 T These numbers are calculated from the table givec in p. 531. 



