SYSTEMATIC ANALYSIS OF APPARATUS. 113 



412. THE WASTE FOOD REQUIRES, of course, merely 

 a separation, when it is at liberty to pass on and leave 

 the body. 



413. THE COOLING FOOD is acids, the precise action 

 of which in preventing the production of heat is not 

 known; but they are without doubt merely dissolved, 

 passed into the blood as acids, and there in some way 

 perform their office. 



414. ONLY TWO CLASSES, the nutritive and the calo- 

 rific, remain to be considered. 



415. IT MUST BE REMEMBERED that the food of ani- 

 mals contains the substances required, not in the condi- 

 tion of chemical elements, but compounded by plants 

 into, or very nearly into, the precise substances needed 

 by the organs. The question is not merely, does an arti- 

 cle or mixture, such as might be made in any chemist's 

 shop, contain the same elements as the Brain or Mus- 

 cles or Bones, but have they the proper form for serving 

 as food, and also can they be readily dissolved ? 



416. IT IS THE OFFICE OF THE PLANT to Compound 



that the animal may decompound. The former synthe- 

 tizes that the latter may analyze. 



417. WHEN ONE ANIMAL EATS ANOTHER, it eats 

 what has before been eaten, and what was a part of a 

 plant at some time. 



418. THE NUTRITIVE PART OF FOOD REQUIRES but 

 little more than to be dissolved out of the substances 

 with which it is combined, and passed into the circulation. 



{Fat. 

 Starch. 

 Gum. 

 Sugar. 

 Gelatin. 



THE FIVE VARIETIES ARE VERY SIMILAR TO EACH 



OTHER in chemical composition will readily burn if 

 thrown into the fire ; each, if fed to a pig, will cause him 



412. What does ? 413. What said of ? 414. What remain ? 415. What 

 - ? 416 What ? 417. What said ? 418. What does ? 419. What said of ? 



