618 SUMMARY OF THE VIEWS LLUSTRATED. 



a larger sustaining supply of food — a larger daily quantity to keep the 

 animal in condition. 



5°. That the fat of the body is generally derived from the fat of the 

 vegetable food — which fat undergoes during digestion a change or trans- 

 formation by which it is converted into the pecuhar kinds of fat which 

 are specially fitted to the body of the animal that eats it. In carnivor- 

 ous animals, the fat is also derived directly from the fat of their food — 

 which is, in like manner, changed in order to adapt it to the constitution 

 of their own bodies. In cases of emergency, it is probable that fat may 

 be formed in the animal from the starch or sugar of the food. 



6°. In the growing animal, the food has a double function to perform, 

 it must sustain and it must increase the body. Hence, if tlie animal be 

 merely increasing in fat, the food, besides what is necessary to make up 

 for the daily waste of various kinds, must also supply an additional pro- 

 portion of oil or fat. To the growing animal, on the other hand, it must 

 .supply also an additional quantity of gluten for the muscles, and of phos- 

 phates for the bones. If to each of a number of animals, equal quantities 

 of the same kind of food be given, then those which require the smallest 

 quantity of food to sustain them will have the largest proportion to con 

 vert into parts of their own substance. Hence, whatever tends to in- 

 crease the sustaining quantity — and cold, exercise, and uneasiness do so 

 — will tend, in an equal degree, to lessen the value of a given weight of 

 food, in adding to the weight of the animal's body. To the pregnam 

 and to the milk cow the same remarks apply. The food is partly ap- 

 pended in the production of milk, and the smaller and leaner the cow is, 

 less food being required to sustain the body, the more will remain for the 

 production of milk. 



7°. Lastly, that the quantity and quality of the dung — while they de- 

 pend in part upon the kind of f(K)d with which the animal is fed — yet 

 even when the same kind of food is given, are materially affected bj-- the 

 purpose for which the animal is fed. If it be full-grown and merely 

 kept in condition, the dung contains all that was present in the food, ex- 

 cept the carbon that has escaped from the lungs. If it be a growing 

 animal, then a portion of the phosphates and gluten of the food are re- 

 tained to add to its bones and muscles, and hence the dung is something 

 less in quantity and considerably inferior in quality to that of the full- 

 grown animal. 



So it is in the case of the milk cow, which consumes comparatively 

 little in sustaining her own body, but exhausts all the food that passes 

 through her digestive organs, for the production of the milk which is to 

 feed her young. 



The reverse takes place with the fattening ox. He takes little else 

 from the rich additional food he eats but the oil with which it is intended 

 that he should invest his own body. Its other constituents are for the most 

 part rejected in his excretions, and hence the richness and high price of 

 his dung. 



Such are the main points I have endeavoured to illustrate to you in 

 this Lecture — they involve so many interesting considerations, both <rfa 



