554 PRACTICE OF PHYSIC. 



be imputed to the same power of habit also, that most epidemics 

 are most violent on their first appearance." 



" Having ascertained the different species of fevers, and as- 

 signed the remote causes of them, we are now in a condition to 

 enter upon the consideration of that variety which does truly 

 occur in epidemic fever. 



" This is one of the most important problems in physic, whe- 

 ther we consider the violence and mortality of these diseases, or 

 the great number of persons affected with them. But there is 

 besides another reason for attempting it : hitherto it has been 

 represented as inexplicable, an opinion of which Dr. Sydenham 

 in particular has laid the foundation. After the observation of 

 many years, he concluded, that the epidemics of every year dif- 

 fer essentially, so that according to his experience he could not 

 judge if the same kind of epidemic might appear again in the 

 same rotation, and consequently he could not pretend to ascer- 

 tain the species and to fix the general method of cure. Dr. Boer- 

 haave, who was not a practitioner when he drew up his aphor- 

 isms, but whose sagacity led him to follow Dr. Sydenham, has 

 unfortunately followed him in this respect also, and he even 

 carries the matter still farther than Sydenham had done. 



" Now there is no foundation for ascribing the variety of 

 epidemics to changes in any of the six non-naturals, although 

 perhaps it might be referred to the atmosphere ; but the inex- 

 plicable variety of the exhalations going on there, would give 

 us hardly any hopes of attaining our purpose ; and the changes 

 we do see occurring in the sensible qualities of the atmosphere 

 leave us without hopes of ascertaining this variety. If this 

 doctrine accordingly be true, that the varieties of exhalations 

 in the atmosphere are truly inexplicable, and that diseases do 

 so immensely differ, we cannot hope to be able to reduce epi- 

 demics to any common or general nature, and to find out a 

 general plan of cure ; we must then be obliged to remain attach- 

 ed to Dr. SydenhanVs plan of studying every epidemic as it 

 arises, and perhaps must destroy several lives before we can 

 learn the method of treating the remainder. But this opinion 

 is not sufficiently well founded, for, from the observations I 



