OP THE CIRCULATION. 339 



XXII. 

 OF THE CIRCULATION. 



Life in the animal body is attended with a 

 never-ceasing change in the whole framework. 

 Not merely is there a current of blood running in 

 a circle, but all the things that enter into the com- 

 position of the animal body, solids as well as fluids, 

 are under an influence that keeps them in inces- 

 sant change. This, indeed, is the object or end of 

 the circulation : for the blood contains in a fluid 

 state what had composed the solid framework. 

 We might say that the solid matter was resolved 

 or melted, but that it is a vital action which thus 

 reduces the'texture to the condition of a fluid. At 

 the same time that the blood contains what has 

 been the material of the body, it consists also of 

 new matter, the product of digestion and assimila- 

 tion, and which is destined to take the place of the 

 material that has been removed. The circulating 

 blood is thus made the agent by which the revo- 

 lution of the solid animal frame as well as of the 

 fluids is accomplished. 



We learn by this, that there is nothing perma- 

 nent in the living body. We see, and perhaps 

 without much surprise, that a part cut heals, that 

 a part excavated or taken away is soon replaced, 



