130 NON-RECURRENCE OF DISEASES. 



the action upon it of a ferment, by which the whole is 

 changed, must be ever the same in amount, although it 

 may not require exactly the same time. If 'the process 

 be less active, it must be proportionally prolonged; if it 

 be more energetic, it will be completed in a shorter time. 

 But the more violent action of a variola is not sooner at 

 an end than the gentler process of a vaccinia, both re- 

 quiring for their completeness about the same period of 

 time. 



Taking it now for granted, that the chemical theory 

 will not satisfy the physiologist or pathologist, I will pro- 

 ceed to make an argument for the non-recurrence, as pro- 

 ducible by the leaving in the system the exuviae of germs. 

 A reference to former parts of these lectures show, that 

 many plants, and especially protophytes, poison, against 

 themselves, the soil in which they grow; and that thus we 

 may, not unsatisfactorily, explain the apparent capricious- 

 ness, as to health, of both places and seasons. Supposing 

 that the cell-germs, animal as well as vegetable, possess a 

 like power when they grow in the animal frame, we can 

 plausibly account for several things not otherwise explica- 

 ble at all. Thus we may presume that some of these 

 exuviee having no emunctory capable of their elimina- 

 tion, remain always where the diseased processes left them ; 

 and thus stand as an obstacle to the future action of simi- 

 lar germs.* We can thus, and thus only, say why certain 

 contagious diseases cannot recur, and why certain diseases 

 which are not contagious, as yellow fever, for example, 

 possess a like disability. Their germs having once re- 

 acted in the body leave behind a poison, or, at least, an 



* Syphilitic poison lurks unexpressed in the system for years, or through 

 life, exemplifying itself only in the offspring. So gout leaps over a genera- 

 tion, in which, however, its cause must be ever present, though latent. 



