Epidemics. 229 



modified change in their modus operandi, as distinct and 

 specific in their action as poisons, either in more intense 

 and generally destructive powers, as in the case of the 

 Black death ; or of a more chronic and milder, yet equally 

 prevading form, as in syphilis, or blended Levant plague 

 with leprosy. If these views are correct, it is not going too 

 far to say that since 1817, when we entered upon a new 

 epidemic era, the blending of the two diseases will slowly 

 but inevitably assume some new or modified form of manifes- 

 tation, or run slowly into one or the other, as hybrids under 

 new circumstances will do, but both, under a new era, in a 

 considerably modified form, to that belonging to their own 

 indigenous epidemic eras.* 



From 103 B.C. to 2347 B.C. is a period of 2,244 years, or 

 thereabouts, and in this period is embraced the Chrono- 

 graphic epidemic period of about 800 years duration or more ; 

 after which period the induction, or great variety, of diseases 

 to which mankind is subjected took their present essentially 

 destructive outlines and demarcations ; which, as ages have 

 gone on, have had a tendency to gradually differentiate, and 

 sufficiently so to demand distinct descriptions and forms of 

 recognition, properly arranged under some general class or 

 order of diseases, as are supplied in Nosological systems. 



Then, from 1491 to 746, or 750 in round numbers, is a 

 period of 741 years. This is considered the period of the 

 settlement of diseases, or that period in which the constant 

 induction of new forms of disease became less frequent, and 

 existing diseases repeated themselves, upon the whole, with 

 greater uniformity and constancy than in the preceding 

 epoch. 



And finally, from 750 to 103 B.C., which embraces a period 

 of 647 years, we begin to enter upon the era of more 



* It may be well to mention that this portion was written some years 

 ago. 



