Lung Plague of Cattle. 607 



the infected districts the great western centres of enterprise and 

 commerce have found it impossible to exterminate the plague. 



In the country districts in England outbreaks were almost ex- 

 clusively confined to the times when fresh cattle were purchased 

 at one of the great fairs. Hence the late autumn, the period of 

 laying in feeding cattle, witnessed the greatest extensions. 



In Ireland, as shown by Ferguson, the whole cattle trade 

 seemed to be arranged as if for the speedy and universal diffusion 

 of infection. Calves, bought by jobbers from all sources, were 

 bunched together with every opportunity for intercommunication 

 and infection. As soon as they were a little further matured, 

 they were assorted in lots and sent to a fair, where they were 

 sold, and found their way to great common pastures, and this 

 process was repeated again and again until they had reached 

 full maturity. On the way to and from each market they were 

 quartered over night in a public yard which had just been vacated 

 by other animals, often diseased, traversed the same roads, and 

 drank and fed from the same troughs which diseased ones had 

 just used. 



The introduction of apparently recovered cattle is generally 

 credited with the infection of a fresh herd and Friedberger and 

 Frohner quote with approval Wallev's assertion that a recovered 

 animal with a sequestrum in the lung can infect a herd into which 

 it is taken. I have failed to produce even local exudate, subeu- 

 tem or in the lung, from sequestra which were much more recent, 

 but the animals operated on were rendered immune and inspired 

 me to carry out a system of immunization by the use of the 

 sterilized fresh exudate. The actual date of the expiration of 

 virulence in the necrotic lung tissue has never been demonstrated 

 and probably varies in different cases. 



The receptivity of different breeds has been discussed and the 

 Holsteins and Shorthorns have been thought to show the greatest 

 susceptibility. These are among the cattle that are most prized, 

 bought and sold, and exposed to infection. The Shorthorn 

 especially has a great development of the circulatory system, in- 

 cluding the connective tissue with its great lymph sacs and chan- 

 nels, and the microbe we are dealing with shows a marked prefer- 

 ence for the lymph system, in which it finds its appropriate field 

 of development. Susceptibility is greatly encreased by a warm 



