16 OBJECTS OF PHYSIOLOGY. 



man ; for, so long as life lasts, the mental and moral 

 powers with which he is endowed manifest them- 

 selves through the medium of organization, and no 

 plan which he can devise for their cultivation, that 

 is not in harmony with the laws which regulate that 

 organization, can possibly be successful. 



But, besides the power of resisting the operation 

 of the ordinary chymical and physical laws, living 

 bodies are distinguished by other properties peculiar 

 to themselves. Unlike inorganized matter, which 

 exists in the same form from the beginning, bodies en- 

 dowed with the principle of life derive their origin 

 from previously existing living bodies of the same na- 

 ture as themselves : these, in their turn, give birth to 

 others, and in this way the succession is kept up. 

 Unlike the inert material which retains its proper- 

 ties unaltered throughout endless ages, the living 

 body is constantly undergoing changes from the first 

 to the last moment of its existence ; and these are 

 exemplified, on the large scale, in the great stages 

 of youth, maturity, old age, and death. Unlike 

 inorganized matter, which neither grows nor de- 

 cays, living bodies require a constant supply of 

 nourishment to admit of their growth in youth, and 

 to replace the worn-out particles which are regu- 

 larly thrown off at every period of life ; and, unlike 

 inanimate objects, the relations and properties of 

 which never alter, living bodies cease at last to 

 exist, and their component elements, deprived of the 

 principle of life, again become subject to the ordi- 

 nary laws of matter, and are speedily decomposed 

 and scattered about as if life had never been. These 

 properties, it maybe observed, are common to vege- 

 table and animal life ; but animals possess others 

 peculiar to themselves. Among the most remark- 

 able of these are sensation, thought, voluntary 

 motion, and the faculty of communicating to each 

 other their own thoughts and feelings, through the 

 medium of natural or artificial language. These 



