6 THE VITAL FUNCTIONS. 



agencies ; but the imitation of the model, even 

 in the smallest part, is far beyond our power. 

 No means which the laboratory can supply, no 

 process, which the most inventive chemist can 

 devise, have ever yet approached those delicate 

 and refined operations which nature silently con- 

 ducts in the organized texture of living plants 

 and animals. 



The elements of organic substances are not 

 very numerous ; the principal of them being 

 oxygen, carbon, hydrogen, nitrogen, sulphur, 

 and phosphorus, together with a few of the alka- 

 line, earthy, and metallic bases. These sub- 

 stances are variously united, so as to form cer- 

 tain specific compounds, which, although they 

 are susceptible, in different instances, of endless 

 modifications, yet possess such a general cha- 

 racter of uniformity, as to allow of their being 

 arranged in certain classes ; the most character- 

 istic substance in each class constituting what is 

 called a proximate organic principle. Thus in 

 the vegetable kingdom we have Lignin, Tannin, 

 Mucilage, Oil, Sugar, Fecula, &c. The animal 

 kingdom, in like manner, furnishes Gelatin, 

 Albumen, Fibrin, Mucus, Entomoline, Elearin, 

 Stearin, and many others. 



The chemical constitution of these organic 

 products, formed, as they are, of but few pri- 

 mary elements, is strikingly contrasted with 

 that of the bodies belonging to the mineral 



