Inoculation for Pleuro- Pneumonia in Cattle. 2G5 



fluid, and therefore we are content to remain among; those who 

 do not advocate the system. As a product of a specific disease, 

 conveyed from animal to animal of the same species, it should 

 produce that disease, upon the principle that "like begets like." 



It is a property of an animal virus, and common to them all, 

 to multiply to an unascertainable extent within the circulating 

 fluids or blood, when introduced into the organism by inocula- 

 tion, and subsequently to centre in some especial part of the 

 body. Usually this part is either directly external, or it has a 

 free communication with the outlets of the body, apparently for 

 the discharge of the morbific matter from the system. We 

 observe these things especially to belong to the virus of small- 

 pox, which is, however, but a type of the class. 



The skin in small-pox becomes the focus of the disease after 

 the multiplication of the poison has been effected. Every 

 vesicle placed on the skin contains the virus ; it therefore par- 

 takes of the same nature, and is capable in the same manner of 

 further extension as was the original vesicle. The inoculated 

 disease is thus proved to be identical with the natural ; it is 

 accompanied with the same symptoms, constitutional and local, 

 and is alike capable of indefinite extension both by infection 

 and contagion. Flow entirely opposed to these laws is the in- 

 oculation of cattle for the prevention of natural Pleuro-pneu- 

 monia. According to Dr. Willems and other advocates of the 

 system, the virus, when introduced, affects the blood ; augments 

 Avithin it ; causes both local and constitutional disturbance ; is 

 reproduced in the areolar tissue of the tail at considerable 

 distance from the site of its insertion ; is capable of being 

 transmitted from animal to animal ; gives immunity against an 

 attack of Pleuro-pneumonia — thus far agreeing fully with the 

 phenomena of genuine inoQ.\x\<ii\on — and yet it never produces the 

 disease, although it not unfrequently destroys the animal even weeks 

 after its employment. 



The pillar on which inoculation stands is that of a disease 

 being capable of transmission from one animal to another by 

 the application of a special cause. Remove this, and it falls. 

 The giving of immunity, or destroying the susceptibility to 

 second attacks of the disease, are but as the ornaments of the 

 capital, adding to its beauty and its value, but not to the necessity 

 of its existence. 



Fortunately, however, for the ends of science, inoculation, or 

 the operation of the special virus of a disease on the body, is 

 so far beneficial, that nature, having freed herself of the materials 

 existing in the organism which are capable of being converted 

 into the same description of virus as that which had been 

 employed in the process, is not again susceptible, as a rule, to a 



