Infecting Animals, Susceptibility. 35 



ately around tliis becomes developed into a tough fibrous 

 envelope, which closes off the dead mass from the adja- 

 cent lung and from all communication with the external 

 air. The dead and imprisoned mass now undergoes a 

 process of breaking down, liquefaction and absorption, 

 commencuig at the surface and slowly advancing toward 

 the centre. The encysted portion of dead lung is one 

 mass of infecting material, and as it undergoes no change, 

 except that of liquefaction, and exhales at no time any 

 putrid odor, it remains infecting so long as it retains the 

 solid form. At the outset more than half a lung may be 

 thus encysted, and five or six months after alleged recov- 

 ery we still find masses of from one to two pounds weight, 

 waiting for the slow process of solution. Whenever there 

 are indications of the existence of such encysted masses 

 the animal should be looked on as infecting and disposed 

 of as summarily as if in the acute stages of the disease. 



Percentage of Animals Susceptible to the Disease. 



The number of animals that contract the disease by 

 exposure to the contagion is somewhat irregular. The 

 French Commission of 1849 found that of 20 animals 

 drawn from a healthy locality and exposed to infection, 

 16 contracted the plague, 10 of them severely. Twenty per 

 cent, remained refractory. In warmer climates the mortal- 

 ity is greater. Dr. Lindley quotes examples from his South 

 African experience, in which whole herds of 80, 130 and 

 several hundred died without exception. We find ap- 

 proximate results in the hot summer of New York, and 

 a reference to cases quoted above will show the destruc- 

 tion of whole herds without exception. During the win- 

 ter season the disease is far less violent in its manifesta- 

 tions and a greater number of exposed cattle resist it. 



Alleged Insusceptibility of the Digestive Oegans. 



In 1868-9 at the Veterinary College at Alfort, portions 

 of the diseased lungs and several pints of the liquid ex 



