336 Elementary Biology. 



or destructive aspect. In the former the formation of new 

 protoplasm (nutrition and assimilation) has to be considered; 

 in the latter, the disintegration of protoplasm and the 

 various phenomena (locomotion, secretion, nervation, &c.) 

 which take place in consequence of that disintegration are 

 the subjects of consideration. 



Anabolism. The first great point of difference which 

 may be noted between the physiology of the plant and that 

 of the animal is the nature of the food-supply in the latter. 

 In the plant (p 190,) we found that the food consisted of 

 chemical elements or exceedingly simple compounds, such 

 as carbonic acid, water, salts of nitric acid, c. ; in the 

 animal, though water and many simple salts are employed 

 as food accessories, yet the essential food-stuffs are derived 

 from already formed products of anabolism. In the long- 

 run all animals are dependent (p. 49) on the plant world 

 for food. Without the assistance of green plants the in- 

 organic constituents found in the environment could not be 

 built up, for the animal, as we have seen, has no power to 

 integrate such simple bodies into protoplasm. The most it 

 can do is to modify arid assimilate already formed com- 

 pounds, employing water and simple salts as accessories. 

 The popular distinction, therefore, of animals into car- 

 nivorous and herbivorous is only superficially correct, since 

 herbivors, on which the carnivors prey, are directly de- 

 pendent on the plant world for food. 



Anabolism in the animal may be said to consist of the 

 following processes : 



(a) Mastication. By the assistance of the teeth, tongue, 

 and muscles of the buccal cavity in the higher forms, or by 

 the gizzard or the masticatory organ of the lower animals, 

 the food, whether it be animal or veget?! in its nature, is 

 divided into small particles, enabling it thereby to be more 

 easily acted on by the juices which are subsequently mixed 

 with it. 



(If) Digestion. The primary object of digestion is, of 



