

PREFACE. 



THE object of the present work is to lay before the British 

 public as complete a view as I can of the present state of the 

 Chemistry of Animal Bodies. This branch of Chemistry is much 

 more difficult than the chemical investigation of vegetable bodies. 

 The difficulty does not lie in the analysis ; for accurate and simple 

 methods of analyzing animal bodies as well as vegetable have 

 been devised ; but in separating the different animal bodies from 

 each other, and obtaining each in a state of purity. These pro- 

 cesses with respect to vegetable bodies are much facilitated by 

 the property which they have of crystallizing. Unfortunately 

 the most important animal substances, as albumen, fibrin, gelatin, 

 casein, &c. want that property. The consequence is, that we 

 have no good criterion for determining when these bodies are 

 pure, or what the substances are with which they are mixed. 

 The consequence of this difficulty has been, that the greater 

 number of modern chemists have confined their investigations to 

 those animal substances, as sugar, cholesterin, cetin, urea, &c. which 

 are capable of crystallizing. I am not aware of any modern 

 British chemist who has attempted to investigate any animal sub- 

 stance incapable of crystallizing. To Dr Wollaston we owe an 



