CHAP. I.] INTRODUCTORY. 13 



animal's body is made up by water, of which it is, therefore, very 

 largely composed, the brain containing about seventy per cent, of 

 that fluid. 



In_ saying that the body consists of different parts and substances, 

 and is made up of combinations of elements, all that is meant is 

 that it can be more or less readily divided into such parts, and that 

 it can be dissolved into such elements, just as water maybe destroyed 

 to give place to oxygen and hydrogen. Whilst living, however, 

 the body really forms one continuous whole locally diff'erentiatod, that 

 is, assuming difi'eront appearances and possessing different properties 

 in different regions. Even the very blood is directly continuous 

 with the other constituents of the body in all actively growing parts. 



