ORGANIC CHEMISTRY. ' 13 



7iic principle. Thus, in the vegetable kingdom we have 

 Lignin, Tannin, Mucilage, Vil, Sitgar, Fecula, &c. The 

 animal kingdom, in like manner, furnishes Gelatin, Mhu- 

 men, Fihnn, Mucus, Entomoline, Elearin, Stearin, and 

 many others. 



The chemical constitution of these organic products, 

 formed, as they are, of but few primary elements, is strik- 

 ingly contrasted with that of the bodies belonging to the mi- 

 neral kingdom. The catalogue of elementary, or simple 

 bodies, existing in nature, is, indeed, more extensive than 

 the list of those which enter into the composition of animal 

 or vegetable substances. But in the mineral world they 

 occur in simpler combinations, resolvable, for the most part, 

 into a few definite ingredients, which rarely comprise more 

 than two or three elements. In organized products, on the 

 other hand, although the total number of existing elements 

 may be smaller, yet the mode of combination in each sepa- 

 rate compound is infinitely more complex, and presents in- 

 calculable diversity. Simple binary compounds are rarely 

 ever met with; but, in place of these, w^e find three, four, 

 five, or even a greater number of constituent elements ex- 

 isting in very complicated states of union. 



This peculiar mode of combination gives rise to a remark- 

 able condition, which attaches to the chemical properties of 

 organic compounds. The attractive forces, by which their 

 several ingredients are held together, being very numerous, 

 require to be much more nicely balanced, in order to retain 

 them in combination. Slight causes are sufficient to disturb, 

 or even overset, this equipoise of affinities, and often pro- 

 duce rapid changes of form, or even complete decomposi- 

 tion. The principles, thus retained in a kind of forced 

 union, have a constant tendency to react upon one another, 

 and to produce, from slight variations of circumstances, a to- 

 tally new order of combinations. Thus, a degree of heat, 

 which would occasion no change in most mineral substances, 

 will at once effect the complete disunion of the elements of 

 an animal or vegetable body. Organic substances are, in 



