2O ANIMAL CHEMISTKT LECTURE I. 



form of urea, and accordingly bears to urea much the same 

 relation that urea itself bears to carbonic acid, thus : 



CN a H 3 (HO) Urea 



CN 8 H 3 (H a N) Guanidine 



I refrain, for the present, from entering into further details 

 upon this subject. I have shown the wide applicability of the 

 generalisation, and that by its means we are capable of associating 

 with one another the most diverse bodies, and of establishing 

 between them the same simple relations which subsist between 

 hydrochloric acid, water, and ammonia ; and in particular I have 

 pointed out that some of the best known products of tissue meta- 

 morphosis are in reality only the ammoniated forms of compara- 

 tively simple bodies. In my next lecture I shall endeavour to 

 satisfy you that the complex character of many organic bodies 

 is more apparent than real, and that most of them may be re- 

 solved into comparatively simple molecules, which are capable of 

 being distributed into certain well denned groups and series ; and 

 I shall take, as concrete illustrations of the point I wish to esta- 

 blish, the composition of salicin among vegetable, and that of 

 hippuric acid among animal products. 



