128 NON-RECURRENCE OF DISEASES. 



is produced by the action of a species of ferment peculiar 

 to it, upon as peculiar a matter contained in the solids or 

 the fluids of the body; by which means said matter is 

 consumed, and thus, is a reproduction of the disease pre- 

 vented by the want of the material upon which the morbid 

 action may be founded. This famous theory of the cause 

 of the production and non-recurrence of certain conta- 

 gious diseases, has great plausibility and a charming sim- 

 plicity. It is, also, supported by analogies deduced from 

 the fermentation of gluten, in the production of bread, 

 and that of saccharine matter in the generation of alco- 

 hol. The fermentable substances having been consumed, 

 the process ceases, and, without the super-addition of new 

 materials, cannot be renewed. 



The objections to the theory of Liebig are both numer- 

 ous and, I think, unanswerable. The existence of the 

 fermentable matters, as well as of the ferment, is purely 

 hypothetical, no proof being offered of the detection 

 of either. It must, also, be observed, that there is, 

 on this hypothesis, a peculiar substance to be acted 

 on, for each of many diseases. Thus there must be one 

 for variola, one for rubeola, one for ^varicella, one for 

 scarlatina, one for pertussis, one for yellow fever, and one 

 for every other non-recurrent disorder. Each of these 

 substances must reside in the system without necessity, 

 and apparently without cause. No influence seems to be 

 exerted by them on the health or structure before disease 

 comes, and their elimination leaves the system unaffected 

 subsequently. But there is presented to my mind a still 

 more important objection, w r hich may be thus stated. 

 For example, every one knows that persons who take 

 small-pox in the natural way, have, usually, severe attacks, 

 a multitude of pustules, and, according to the theory, a 

 very extensive fermentation, and a reproduction of a large 



