in its Relations to Physiology. 427 



It was the phlogiston latent in bodies which was supposed to acquire 

 motion, and to escape by the action of heat, and it was deemed perfect- 

 ly rational to conclude that the properties of bodies must depend upon 

 a certain proportion of phlogiston, salt, and earth, and that the 

 metals should owe to phlogiston their hardness, their ductility, and 

 their lustre. All was consistently enough explained. The existence of 

 phlogiston seemed beyond a doubt, no one thought of attempting to 

 prove it by any special argument. For were there no phlogiston there 

 would have been no explanation of the phenomena. No phenomenon 

 would have been explicable without phlogiston, all would have been 

 darkness and doubt. 



The advantage which the hypothesis of phlogiston presented at that 

 time was that it kept together the ascertained facts and led to discoveries, 

 as it served as a guide and stimulus to the search for new facts. The 

 benefits of such an hypothesis are obvious enough ; and yet, after all, 

 it was nothing more than a mere description of phenomena — a word 

 which embraced the effects of many causes, and which word was taken and 

 considered as the ultimate cause itself. 



At length the period arrived when this word lost its use and significa- 

 tion, when the better and more correct knowledge, the offspring of 

 phlogiston, devoured its parent. The more minute and comprehensive 

 study of heat, in specific and radiated caloric, the more exact determina- 

 tion of the individual letters composing the word phlogiston, led to the pre- 

 sent state of chemistry, and the method arising from the study has led 

 to the more profound and correct apprehension of chemical processes, 

 and the causes by which chemical phenomena are produced, the intro- 

 duction of which into physiology, pathology, and therapeutics, is the 

 great desideratum of the present time. 



The method of the phlogistic philosophers reached its climax in natural 

 philosophy, and with this blossom the plant died, the leaves thereof faded, 

 and the stem mouldered! The true fruit of it was the irresistible con- 

 viction which was forced upon every thinking and reasoning mind that no 

 enduring results could be obtained by its means. New and better me- 

 thods of investigation took its place, and herewith the essential condi- 

 tion was reached of a real and sound progress. Who does not recognise 

 in the "vital principle" of the physiologists the old phlogiston theory 

 dressed up and disguised in medical rags? As soon as you deprive 

 them of this convenient phantasm all their explanations vanish into 

 thin air ! The simple search for phlogiston created a new science in 

 chemistry ; the search after the " vital principle" is preparing a new era 

 in the medical sciences. 



