340 NATURAL THEOLOGY 



and in some of the lower animals that members 

 cut off are actually reproduced : all this we see, 

 but it requires fine experiment and accurate rea- 

 soning to enforce the conclusion that the animal 

 body is always growing, always forming ; and that 

 this incessant revolution in the material of the 

 frame is the grand distinction between the living 

 structures of the animal body and machinery. In 

 the former there is a principle of renovation inces- 

 santly at work, so that the action or exercise is at- 

 tended with no wear and tear, but, on the contrar}% 

 the greater the activity the more perfect the struc- 

 ture, and what we term the healing process, or the 

 reproduction of parts, is the continuance of an ac- 

 tion which has had no interval. 



It being absolutely proved that there is nothing 

 permanent in the body, we leave the reader to 

 consider the question, which forces itself upon 

 him, " What, then, is it that gives identity? How 

 comes the peculiarity of form and constitution and 

 complexion to remain — or how does the memory 

 serve us — when the material has been many times 

 removed ?" But we have rather to consider the 

 grand operation by which these changes are 

 wrought — the circulation. 



Modern chemists have estimated that 5208 

 grains of charcoal are thrown off from the blood 

 in twenty-four hours, and this uniting with 13,392 

 grains of oxygen in the atmosphere that is breathed, 

 constitutes, with a due proportion of caloric, the 

 carbonic acid gas which is discharged from the 



