ZYMOSIS. 15 



PHLOGISTON. 



But amid these fantasies there was a deep vein of earnest 

 observation and thought. Physicians saw a pestilence strike 

 a community as a spark strikes among shavings, and kindling, 

 attack person after person in society, as fire would leap from 

 house to house in a city. Sydenham says : " Ita ignis ignein 

 generat et maligno infectus morbo socium inficit." 



Stahl supposes a principle of inflammability or the matter 

 of -fire in composition with other bodies, an hypothetical 

 element supposed to be pure fire, fixed in combustible bodies, 

 in order to distinguish it from fire in action or in a state of 

 liberty. This was called " Phlogiston." A similar supposi- 

 tion obtained in regard to epidemic and contagious diseases, 

 viz., that there was some substance or force in man himself, 

 which, when once put in motion, acted similarly to fire and 

 spread with deadly effect. To this day, remedies directed 

 against inflammation or inflammatory conditions are called 

 an tiph logistics. This theory of the origin and propagation of 

 epidemic diseases seems to have been much discussed. 



ZYMOSIS. 



Another hypothesis was based on the known action of fer- 

 ments, which is maintained to this day, the present germ 

 theory being considered within the limits of this hypothesis. 

 It was seen that yeast, when added to certain compounds con- 

 taining sugar, caused certain phenomena. That a very small 

 quantity of the yeast was necessary for a beginning, and that 

 this would be reproduced continuously. It could be carried 

 from vat to vat of grape juice for any number of times, and 

 the more fermentation accomplished the more the ferment 

 increased. It was found, also, that this kind of fermentation 

 would begin, but less promptly, without the addition of yeast, 

 and that in this case also the yeast was formed. Now they 



