HOW THE ANIMAL LIVES 209 



357. This cell can flow out so as to surround 

 microscopic particles and draw them into itself ; 

 these it can digest and use to increase its own 

 substance. By reversing this process, it can 

 throw out indigestible and waste materials. It 

 can absorb, digest and build into its own sub- 

 stance nutritive matters already dissolved in 

 water; and it can drive out waste, worn out and 

 injurious matters which it holds in solution in its 

 own liquid. 



358. When the cell grows too large, it can 

 divide into two independent parts, each having 

 all the vital powers which belonged to the parent 

 cell or globule. 



359. Thus the single -celled animal can make 

 of any part of its body limbs for moving, hands 

 for grasping, fingers for feeling, stomach for 

 digesting, channels for the circulation of its 

 nutritive liquids, as well as organs for excretion 

 and for the increase of its kind. 



Ic. Many -celled animals 



360. In all the higher animals there is not one 

 cell, but myriads ; and these cells are no less 

 essential to life and to the healthy performance 

 of all vital functions than is the single cell of 

 the lowliest organism. In the complex animal 

 body, however, the cells build up solid tissues 



N 



