160 Epidemics. 



Hence, in extension of disease in epidemic periods, 

 isolation is an essential feature in its diffusion and onward 

 development. Moreover, it is common to have excess of 

 development in the insect world and lower forms of animal life 

 in particular kinds or grooves, whilst a higher class, or man, 

 falls a victim to special forms of disease in great numbers and 

 wide areas; but in such way that it is in its destructive 

 powers subject to law and order. For what is a particular 

 disease, but the imprint or law of that particular epidemic ? 

 And what is the diffusion of that disease but the order in 

 which the law is extended and adjusted in its application ? 



Such a thing as a general diffusion of death or disease in 

 equal ratio and proportion to all organized beings and 

 objects, within a given area, is unknown and has no exist- 

 ence. Epidemium is always in its diffusion and application 

 special and limited ; and in its principle of distribution is 

 conformable to the law of isolation. 



Thus, in 1831-32 and 1849, cholera was a diversion of 

 vital force in a particular form of limitation to human life ; 

 gangrene of the spleen in Russia; influenza in North 

 Europe, 1837; potato famine in 1846 and rinderpest in 

 1869, are all samples of vital force acting in special forms 

 of deterioration or perversion to health. 



CONCERNING THE PROGRESS OF EPIDEMICS. 



It is important to observe that upon the whole epidemics 

 are progressive in their area of diffusion, and for the most 

 part radiate from some particular or endemic area as 

 cholera from the Ganges, leprosy from Egypt, and the plague 

 from the Levant. Also in their duration certain particular 

 types last for centuries, then gradually decay. 



Supposing these remarks are illustrated by four well- 

 established diseases or epidemics leprosy, Levant or bubonic 

 plague, small-pox, and cholera more light will be thrown 

 upon the subject generally. 



