5 ANIMAL CHEMISTRY LECTURE III. 



the residues of isethionic acid and ammonia, &c., as referred to in 

 my last lecture. It must be observed, however, that the neglect 

 of these syntheses did not arise so much from want of interest in 

 the production of the bodies, as from want of knowledge of their 

 intimate constitution. No sooner, for instance, was the constitu- 

 tion of the above four compounds satisfactorily made out than they 

 were obtained artificially by Berthelot, Volhard, Dessaignes, and 

 Strecker and Kolbe respectively ; and as it has been with these, 

 so doubtless will it be with many other complex tissue products, 

 with the constitution of which we are as yet imperfectly ac- 

 quainted. 



(58.) The first stage of the process of organic synthesis, how- 

 ever, or the building up of the primary oxihydrocarbon mole- 

 cules, was considered until very recently as altogether beyond the 

 art of the chemist. It used to be thought that chemistry was 

 essentially incompetent to the production not only of organised, 

 but of organic bodies. For the production of these bodies, the 

 intervention of some living organism, the expenditure of some 

 vital force whatever that might be was considered absolutely 

 necessary. While the constituent atoms of a piece of alum, for 

 instance, were admittedly held together by mere mechanical and 

 chemical forces, the atoms of a piece of sugar, on the other hand, 

 or of a piece of fat, were conceived to be put together in some 

 ; mysterious way by vital forces. These opinions were originally 

 \ propounded by Berzelius at a time when the then state of know- 

 | ledge may possibly have justified their enunciation. They re- 

 [ mained almost unchallenged for a long series of years, and are 

 I still asserted in some recent text-books with a degree of dog- 

 matism altogether opposed to the present advanced state of know- 

 ledge* on the subject. 



(59.) The great progress recently made in the constructive art 

 of the chemist is, I think, a topic of sufficient interest to war- 

 rant me in entering into further detail upon the heretofore 

 accepted opinions, which I find expressed very well in the last 

 edition but one of Liebig's Chemical Letters the last edition that 

 was translated by Dr. Gregory, who, writing in 1851, says: 



