CORRELATION OF VITAL AND PHYSICAL FORCES. 165 



animal only for force and repair. Plants use food for force and growth 

 —they never stop growing. 



Now, the food of animals is of two kinds, amyloids and albumi- 

 noids. The carnivora feed entirely on albuminoids ; the herbivora on 

 both amyloids and albuminoids. All this food comes from the vege- 

 table kingdom directly in the case of herbivora, indirectly in the case 

 of carnivora. Animals cannot make organic matter. Now, the tissues 

 of animals are wholly albuminoid. It is obvious, therefore, that for 

 the repair of the tissues the food must be albuminoid. The amyloid 

 food, therefore (and, as we shall see in carnivora, much of the albumi- 

 noid), must be used wholly for force. As coal or wood, burned in a 

 steam-engine, changes chemical into mechanical energy, so food, in 

 excess of what is used for repair, is burned up to produce animal ac- 

 tivity. Let us trace more accurately the origin of animal force by 

 examples. 



10. Carnivora. — The food of carnivora is entirely albuminoid. 

 The idea of the older physiologists, in regard to the use of this food, 

 seems to have been as follows : Albuminoid matter is exceedingly un- 

 stable ; it is matter raised, with much difficulty and against chemical 

 forces, high, and delicately balanced on a pinnacle, in a state of unsta- 

 ble equilibrium, for a brief time, and then rushes down again into the 

 mineral kingdom. The animal tissues, being formed of albuminoid 

 matter, are short-lived ; the parts are constantly dying and decom- 

 posing ; the law of death necessitates the law of reproduction ; decom- 

 position necessitates repair, and therefore food for repair. But the 

 force by which repair is effected was for them, and for many physiol- 

 ogists now, underived, innate. But, the doctrine maintained by me in 

 the paper referred to is, that the decomposition of the tissues creates 

 not only the necessity, but also the force, of repair. 



Suppose, in the first place, a carnivorous animal uses just enough 

 food to repair the tissues, and no more — say an ounce. Then I say the 

 ounce of tissue decayed not only necessitates the ounce of albuminous 

 food for repair, but the decomposition sets free the force by which the 

 repair is effected. But it will be perhaps objected that the force would 

 all be consumed in repair, and none left for animal activity of all kinds. 

 I answer : it would not all be used up in repair, for, the food being al- 

 ready albuminoid, there is probably little expenditure of force necessary 

 to change it into tissue; while, on the other hand, the force generated 

 by the decomposition of tissue into C0 2 , H 2 0, and urea, is very great — 

 the ascensive change is small, the descensive change is great. The de- 

 composition of one ounce of albuminous tissue into CO a , H a O, and urea, 

 would therefore create force sufficient not only to change one ounce 

 of albuminous matter into tissue, but also leave a considerable amount 

 for animal activities of all kinds. A certain quantity of matter, run- 

 ning down from plane No. 4 to plane No. 2, creates force enough not 

 only to move the same quantity of matter about on plane No. 2, but 



