76 FEEDING ANIMALS. 



animala is recovered in the excrements, together with the 

 increase in the weight of the body. 



RESPIRATORY PRODUCTS. With a view of further de- 

 termining the correctness of the conclusions above stated, 

 Grouven experimented upon the direct products of respi- 

 ration to determine whether any ammonia may pass off 

 through the lungs or skin, and found a mere infinitessimal 

 quantity of this gas thus excreted; thus confirming the 

 previous conclusion. 



And experimenters propose to determine the gain or loss 

 of flesh in an animal by comparing the whole amount of 

 nitrogen in the food with the whole amount of nitrogen 

 in the excrements. If the nitrogen in the excrements is 

 less than in the food, then the animal is gaining in flesh, 

 but if more in the excrements, then the animal is losing 

 flesh. 



Carbon is excreted from the body partly in the urinary 

 excretions, but more through the lungs and skin. 



Hydrogen is excreted partly in the urea but mostly in the 

 form of water. 



EXCRETION OF ASH CONSTITUENTS. The ash or min- 

 eral matter of the food is excreted in the urine and in the 

 solid dung. Liebig held that phosphoric acid was generally 

 not found in the urine of herbivorous animals because this 

 liquid is nearly always alkaline, and fodder generally con- 

 tains much lime which unites with the phosphoric acid, 

 forming phosphate of lime. Phosphate of lime being in- 

 soluble in alkaline fluids, and thus phosphoric acid is not 

 likely to be found in the urine except when there is more 

 than can unite with the lime. Bertram found that when 

 magnesia takes the place of the lime, phosphoric acid ap- 

 pears in the urine, even when that is alkaline. When the 

 food is rich in phosphoric acid and comparatively poor in 



