THEIR MODE OF ACTION. 397 



All the characters of the phenomena of contagion 

 tend to disprove the existence of life in contagious 

 matters. They without doubt exercise an influence 

 very similar to some processes in the living organ- 

 ism; but the cause of this influence is chemical 

 action, which is capable of being subdued by other 

 chemical actions, by opposed agencies. 



Several of the poisons generated in the body by 

 disease lose all their power when introduced into 

 the stomach, but others are not thus destroyed. 



It is a fact very decisive of their chemical nature 

 and mode of action, that those poisons which are 

 neutral or alkaline, such as the poisonous matter of 

 the contagious fever in cattle [typhus contagiosus 

 ruminantium), or that of the smallpox, lose their 

 whole power of contagion in the stomach ; whilst 

 that of sausages, which has an acid reaction, retains 

 all its frightful properties under the same circum- 

 stances. 



In the former of these cases, the free acid present 

 in the stomach destroys the action of the poison, 

 the chemical properties of which are opposed to it ; 

 whilst in the latter it strengthens, or at all events 

 does not offer any impediment to poisonous action. 



Microscopical examination has detected peculiar 

 bodies resembling the globules of the blood in ma- 

 lignant putrefying pus, in the matter of vaccine, &c. 

 The presence of these bodies has given weight to 

 the opinion, that contagion proceeds from the de- 

 velopment of a diseased organic life ; and these for- 

 mations have been regarded as the living seeds of 

 disease. 



This view, which is not adapted to discussion, has 

 led those philosophers, who are accustomed to search 

 for explanations of phenomena in forms, to consider 

 the yeast produced by the fermentation of beer as 

 possessed of life. They have imagined it to be com- 

 posed of animals or plants, which nourish themselves 

 from the sugar in which they are placed, and at the 



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