154 Epidemics. 



spread agency than can be conceded to any mere local 

 cause, and, from receiving the title of endemic disease, are 

 transferred to the more extended field of epidemic disease, the 

 first point that attracts the attention is the selection which 

 epidemics make out of the vast range of organized products; 

 for if endemics select a limited area, or given trades, etc., 

 epidemics select kinds of diseases, and special objects of 

 attack, in such way and manner that one attribute of 

 epidemics may be recognized as that of isolation. 



It may be illustrated in the following manner. In 1771 

 mildew attacked the wheat crops in the United States of 

 America and oats in Scotland, whereby these cereals, in 

 their respective countries, yielded a most defective harvest. 

 In 1830 to 1832, potatoes were considerably diseased in 

 America, Germany, and Ireland, probably in the form of a 

 fungi adhering to the fibrillse or roots of the bulbs, occasion- 

 ing a drying or withering of the bulb itself. But in 1845-6 

 Great Britain, Ireland, and a large portion of Europe 

 suffered from severe epidemic potato disease, spreading 

 over whole fields and countries with fearful rapidity, and 

 as a deadly plague the leaves and stems turning black and 

 lifeless, and in another week or ten days the entire crops 

 would become like charnel-houses of corruption and stench. 

 This destructive disease still lingers in Europe, and in the 

 Emerald Isle is a greater curse to the land than the plague 

 of frogs in that charmed land of cabins and domestic stock. 



What can be said of bulbs, cereals, smaller plants, 

 and shrubs can scarcely be applied with propriety to 

 vegetable organism of a larger growth, since disease 

 may attack the flowers or fruit of vegetables of larger 

 growth; but, as yet, no instance is recorded of the destruc- 

 tion of our larger trees, such as belong more especially to 

 the forests and parks, as the oak, the elm, the beech, the 

 cocoanut tree, mahogany or cedar trees. 



