8 HUMAN PHYSIOLOGY 



functions. Indeed, one might very well correctly 

 express the opinion warranted by scientific con- 

 siderations, that if we take into account man's 

 mental powers alone, dependent upon the possession 

 of a highly developed brain, these characters would 

 entitle the human being to a kingdom to himself in 

 the animal sphere. 



OUR BODILY CONSTITUTION. The complexity of 

 the human body becomes resolved into a certain 

 degree of simplicity, when we discover that under 

 the single personality which a human being re- 

 presents, there is included all the elements of a 

 compound commonwealth. When the constitution 

 of the body is closely scrutinised, we find that 

 ultimately its component units become resolved into 

 collections of microscopic bodies to which the name 

 of cells has been given. In certain parts of the body 

 it is true there are fibres to be found, these being 

 represented by the muscles or flesh of the frame, by 

 the ligaments of bones binding them together in the 

 joints, and by the nerve fibres of which the nerves 

 are composed, these last representing the telegraph 

 wires of the body conveying messages to and from 

 the external world. But as fibres themselves origin- 

 ate from cells, and, what is more to the point, as the 

 whole body to start with is developed from one single 

 cell known as the ovum or egg, we may readily 

 understand how the cell may be taken as the typical 

 unit of the whole body. Hence the history of cells 

 forms the starting point for all satisfactory con- 

 siderations which deal with the body's constitution. 



THE CELL. The modern conception of the cell is 

 that of a microscopic speck of protoplasm or living 

 matter which may vary from the 1 -120th part of an 

 inch in diameter a size represented in the ovum or 



