HANDBOOK OF PHYSIOLOGY. 



CHAPTER I. 



ON THE GENERAL AND DISTINCTIVE CHARACTERS OF 

 LIVING BEINGS. 



HITMAN PHYSIOLOGY is the science which, treats of the 

 life of man of the way in which he lives, and moves, and 

 has his being. It teaches how man is begotten and born ; 

 how he attains maturity ; and how he dies. 



Having, then, man as the object of its study, it is un- 

 necessary to speak here of the laws of life in general, and 

 the means by which they are carried out, further than is 

 requisite for the more clear understanding of those of the 

 life of man in particular. Yet it would be impossible to 

 understand rightly the working of a complex machine 

 without some knowledge of its motive power in the sim- 

 plest form ; and it may be well to see first what are the 

 so-called essentials of life those, namely, which are mani- 

 fested by all living beings alike, by the lowest vegetable 

 and the highest animal, before proceeding to the consider- 

 ation of the structure and endowments of the organs and 

 tissues belonging to man. 



The essentials of life are these, birth, growth and 

 development, decline and death and an idea of what life 

 is, will be best gained by sketching these events, each in 

 succession, and their relations one to another. 



The term, birth, when employed in this general sense 

 of one of the conditions essential to life, without reference 



