Epidemics. 179 



but 150 to 200 years after 1 177 which is the next epidemic era 

 the already rising cloud begins to thicken up to 1670 to 1680, 

 and thunderclap after thunderclap drops down its showers of 

 pestilence and disease in the form of small-pox and plague 

 in every city in Europe, and all the known world. Here in 

 one ten years, there in another ten years, then twenty, then 

 thirty, and then again simultaneously over all Europe and 

 Asia ; the most terrible and fatal storm of disease occurring 

 in the form of Black death between 1348 and 1357, the three 

 first years being the worst. 



A curious and interesting enquiry presents itself in this 

 Black death, which may be counted worthy of a passing 

 notice, or, if it may be so styled, an attempt to break ice. 



First : Can two diseases run parallel in the same body at 

 the same time ? 



Second : Can two diseases amalgamate or coalesce, and 

 out of that coalescence produce one new disease or hybrid ? 



First : Those who have seen much of scarlatina, measles, 

 and small-pox, will have seen these affections running 

 parallel with each other in the same person at the same 

 time occasionally. Varicella, with measles or scarlatina, 

 is not very infrequent ; but the varicella in such cases is, 

 though distinctive, of a very mild form, and the size of the 

 pustule is very small. So far as personal knowledge is 

 concerned, the infection is quite as active when combined as 

 when either is distinct, but the severity of the attack is 

 much milder and the duration shorter. The first few hours 

 of appearance of the rash appear to be the most trying to 

 the constitution ; that passed, the two affections appear 

 to modify each other, and to put a bar to each other's 

 intensity ; so that molecular change or cell nutrition under- 

 goes less trial to its own processes of nutrition than when 

 either runs its course alone. Variola and measles are 

 rarely seen in the same person at the same time ; and by the 



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