SANGUIFICATION 229 



aeration as it may be termed, in common with 

 an analogous process in vegetables, takes place. 

 In all vertebrated animals the blood has a red 

 colour, and it is also red in most of the Anne- 

 lida; but in all other invertebrated animals, it 

 is either white or colourless.* We shall, for the 

 present, then, consider it as having undergone 

 this change, and proceed to notice the means 

 employed for its distribution and circulation 

 throughout the system. 



Chapter X. 



Circulation. 



§ 1. Diffused Circulation. 



Animal life, implying mutual actions and re- 

 actions between the solids and fluids of the body, 

 requires for its maintenance the perpetual trans- 

 fer of nutritive juices from one part to another, 

 corresponding in activity to the extent of the 

 changes which are continually taking place in 

 the organized system. For this purpose we 



* Vauquelin has observed that chyle has often a red tinge in 

 animals. 



