FIRST CASES OF EPIDEMICS. 131 



impediment, by which their future reaction is there pre- 

 vented. 



But certain contagious, and even non-contagious diseases, 

 obviously dependent on germs, have the power of recur- 

 rence for many times. Yet even these are subject, at 

 least temporarily, to the same law; for, otherwise, none of 

 these diseases could have a termination. The impedi- 

 mental matter being either emulged or decomposed, after a 

 period, shorter or longer, according to each disease, leaves 

 the system open to a reinfection ; and thus syphilis, favus, 

 and aphthee may, for many successive times, disturb the 

 health of the same individual. 



Returning to the immediate object of the present lec- 

 ture, I proceed to explain why it is that the first cases of 

 an epidemic are usually so much more fatal than those 

 which follow them. This is especially true of the diseases 

 of a miasmatic character and non-contagious maladies, 

 such as yellow fever and cholera. Toxication, when of 

 vegetable origin, is made less potent by habit. Thus, in 

 process of time the habitual drinker or opium eater, tole- 

 rates enormous doses of alcohol or opium. Nay, even when 

 made as obviously drunk even to insensibility, the old 

 toper is in less immediate danger than the beginner. His 

 organism recovers better, and while the novice dies poi- 

 soned or apoplectic, the snoring habitual drunkard reco- 

 vers from his coma and cerebral congestion. Thus is it 

 with those who are toxicated by an atmospherically con- 

 veyed fungous poison. At first it proves eminently fatal; 

 subsequently, although its symptomatic expression may 

 be as strong, its danger steadily decreases, until at length 

 almost every case recovers. 



For this reason, medical men, at the commencement of 

 a violent epidemic, are driven too often from a treatment 



