14 Introduction. 



Disease of a special character has been in the potato for 

 long ; neither have onions nor yet turnips been exempt ; and 

 could man's knowledge scan far enough, he would find all 

 bulbous and cereal growths, at times, subject to much 

 disease, but never several kinds at one period. 



In man, and the higher orders of animals, the isolation 

 chiefly recognised is that of special organs. As in yellow 

 fever, the chylopoietic organs are chiefly involved ; in 

 cholera, the chest organs and mucous membrane generally. 

 In influenza, chiefly the lungs ; occasionally a single organ 

 is picked out with extreme exactness, as the spleen, in one 

 part of Russia, in 1831. Since 1846 the chest organs in 

 horned cattle have been specially attacked, and later on, 

 rinderpest, has shown itself as a peculiar form of infectious 

 diseases, namely, as an eruptive disease from blood-poison- 

 ing, but less special in its seat than any known epidemic 

 disease, for scarcely an organ or surface of the body is free 

 from its special form of elimination. 



From these considerations it is assumed that vital force 

 is always subject, in its manifestation as an epidemic, to 

 some specific form of presenting its own power in any 

 given tenement, and so to favour the law of isolation, 

 rather than the withdrawal of equal degrees or amounts of 

 force ; and, fjy isolation, in a measure, suffering the machine 

 to destroy itself by perversion of one or more functions, 

 rather than by mutilating all consecutively. 



In other words destruction to life, or limiting it for a 



