426 Observations on Organic Chemistry 



they witnessed and effects they studied were referred to the chemical 

 operations of the animal fluids. But the definitions of acid, alkali, and 

 fermentation, upon which they relied, and which they had borrowed 

 from chemistry, failed, and these terms gradually acquired a very dif- 

 ferent signification. 



The first principle of medical chemistry, namely, to take experience 

 and experiment alone as the foundation and touchstone of theory, was 

 altogether lost sight of in the explanation of vital phenomena, just be- 

 cause true experience — the real science of chemistry — could not keep 

 pace with the progress of physiology and anatomy. 



Thomas Willis, by giving an effectual impulse to the development of 

 anatomy, prepared the overthrow of iatro-chemistry. Henceforth the 

 solid parts of the body were more carefully and particularly studied, 

 and the functions of the various organs, and every step in the progress 

 of advancement made more and more evident the insufficiency of iatro- 

 chemistry. The result was an estrangement and separation of medicine 

 from chemistry. But never, not even during the prevalence of the 

 theory of phlogiston, were chemical investigations and principles con- 

 sidered as non-essential to the apprehension of pathological and the- 

 rapeutical phenomena. With a truly scientific spirit Boerhaave assert- 

 ed the necessity of chemistry to medicine, pointed out their true rela- 

 tions, and exposed the folly of the iatro-chemists, and the vanity of 

 alchemy. 



Galileo, Kepler, Torricelli, and Lord Bacon, deposited in its grave the 

 Aristotlean method of considering and explaining natural phenomena, so 

 far as regarded its employment in natural philosophy, but they were 

 unable to exercise any influence upon the theory of medicine, because 

 chemistry itself, the foundation-stone of medicine, being threatened at 

 that time in its own existence and independence as a science, found 

 protection — a point of reliance and support, in the philosophical method 

 of Aristotle. 



The hypothesis of phlogiston, and the part it performed in natural 

 phenomena, was, in fact, nothing more nor less than the union and in- 

 corporation of certain effects observed in nature, just in the same man- 

 ner as the designation of other elements, air, water, earth, were incor- 

 porations of the conceptions of gaseous fluid and solid states of matter, 

 and, at a later period, sulphur and mercury were general expressions 

 of inflammability and metallic qualities. 



The existence of phlogiston once assumed, the evolution of light and 

 heat in combustion, and the alterations which substances undergo in 

 chemical processes, were explained in the most satisfactory manner. 



