32 BUILDING UP AND PULLING DOWN OF THE PARTS. 



of the solid food into a semi-fluid state, shows that the common 

 salt of the food from one of the constituents of which, its 

 chlorine, muriatic acid is formed is closely connected with a 

 healthy state of digestion. 



4. The building up of the several parts of its body with the 

 substances extracted from the food, is another important duty 

 of the living animal. We have already seen that for this pur- 

 pose the raw materials of which muscle, fat, and bone consist, 

 are prepared by the plant, and conveyed ready formed into the 

 stomach. These substances are extracted from the vegetable, 

 and conveyed to those parts of the body which, because of their 

 increasing size, require new materials, or to which they are 

 necessary for the purpose of replacing that which is naturally 

 removed. 



5. Pulling down we may familiarly call that function of the 

 healthy animal body, by which its several parts are made to 

 undergo a constant and gradual removal. No sooner are the 

 parts of the body built up, even in the full-grown animal, than 

 they begin to be taken down again. The portions as they are 

 removed, or perhaps in order to their removal, are decomposed 

 and carried off, to be rejected in the animal excretions. In 

 three to five years every part of the body is removed and 

 renewed in this way, and the nature and daily amount of this 

 natural waste form fundamental considerations in all discussions 

 or suggestions on the subject of feeding. 



6. Excreting is the final function exercised by the animal in 

 reference to its food. What the stomach does not fully reduce 

 to a fluid form, and all which, being so reduced, is not taken up 

 by the absorbing vessels, passes downward along the alimentary 

 canal, and is finally rejected either in the urine or in the solid 

 excretions. That which is removed from the body itself, also, 

 through the influence of the causes which produce the natural 

 waste, passes off and is rejected in the same manner. And in 

 reference to this, it is not unuseful to bear in mind, that the 

 characteristic element of the muscles and cartilages, their 

 nitrogen, passes off in the urine; while the equally characteristic 

 ingredient of the bones, their phosphoric acid, passes off in the 

 solid excretions. Carnivorous and omnivorous animals, only, 



