PREFACE. XI 



With all its discoveries, modern chemistry has 

 performed but slender services to physiology and 

 pathology ; and we cannot be deceived as to the 

 cause of this failure, if we reflect that it was found 

 impossible to trace any sort of relation between the 

 observations made in inorganic chemistry, the know- 

 ledge of the characters of the elementary bodies and 

 of such of their compounds as could be formed in 

 the laboratory, on the one hand, and the living 

 body, with the characters of its constituents, on the 

 other. 



Physiology took no share in the advancement of 

 chemistry, because for a long period she received 

 from the latter science no assistance in her own 

 developement. This state of matters has been 

 entirely changed within five-and-twenty years. But 

 during this period physiology has also acquired new 

 ways and methods of investigation within her own 

 province ; and it is only the exhaustion of these 

 sources of discovery which has enabled us to look 

 forward to a change in the direction of the labours 

 of physiologists. The time for such a change is now 

 at hand ; and a perseverance in the methods lately 

 followed in physiology would now, from the want, 

 which must soon be felt, of fresh points of departure 

 for researches, render physiology more extensive, 

 but neither more profound nor more solid. 



