BY PASSING THROUGH THE BODIES OF ANIMALS. 473 



Carbon. Nitrogen. Saline matter. 



In the potatoes 1716 grs. 47 grs. 196 grs. 



In the bread 1004 " 34 " 22 " 



In the beef 790 " 120 " 35 " 



^510 grs. 201 grs. 253"grs. 



And he has given off in respiration 2625 " 



Leaving to be rejected sooner or 



later in the excretions 885 " 201 " 253 " 



In this supposed case, therefore, the carbon, nitrogen, and saline 



matter were to each other nearly as the numbers 



Carbon. Nitrogen. Saline matter. 



•35 2 2h in the food, 



and as 9 2 2h in the excretions : 



Or, in other words, the carbon being in great part sifted out of the 

 food by the lungs, the excretions are necessarily much richer in ni- 

 trogen and in saline matter, weight for weight, than the mixed vege- 

 table and animal matters on which the man has lived. 



But the immediate and most sensible action of animal and vegetable 

 substances, as manures, depends upon the proportion of nitrogen and sa- 

 line matters they contain. This proportion, then, being greater in the ex- 

 cretions than in the crude vegetables, the cause of the higher estimation 

 in which the former are held by the practical farmer is sufficiently clear. 



2°. In the above case I have supposed the allowance of food to be 

 such only as a person of sedentary habits would consume, and the 

 quantity of carbon given off from the lungs to be such as his habits 

 would occasion. But if the weight of carbon given off from the lungs 

 and skin together amount, as it often does, to 15 ounces,* the quantity 

 of food must be greatly increased beyond the quantity I have stated, 

 if the health and strength are to be sustained. By such an increase 

 of food — the carbon being removed by respiration — the proportion of 

 nitrogen and of saline matters in the excretions may be still further 

 increased, or as manures they may become still richer and more irrir- 

 mediately fertilizing. 



3*^. Let me present to you the results of an actual experiment made 

 by Boussingault upon a horse fed with hay and oats — and of which 

 both the food and the excretions were carefully analysed. 



In 24 hours the horse consumed — 



Carbon. Nitrogen. Saline matter. 



Hay, 16i lbs..t containing 45,500 grs. 1,500 grs. 8,960 grs. 



Oats, 5 lbs..' 15,000 » 650 " 1,180 « 



Total in the food 60,500 " ~2,150 « lO^lio"" « 



And gave off from the lungs & skin 37,960 " 



Leaving to be rejected in the ex- 

 cretions 22,540 " 2,150 " 10,140 " 



While there was actually found in 

 the mixed dung 22,540 « 1,770 " 10,540 " 



• Liebig estimates the quantity of carbon which escapes from the lungs and skin of a 

 healthy man, taking moderate exercise, af, 13-93 ounces (Hessian), or 15>^ ounces avoirdu- 

 pois, in 24 hours. 



t Each containing about 14 per eant. of vf&ter.—AnTiales <l* Jhim. et de Pht/s., Ixx!., p. 136. 



