Lung Plague of Cattle. 605 



denied by one veterinary teacher in Great Britain in the latter 

 half of the 19th century. The transmission of the disease by 

 mediate contagion was denied by those in authority in Great 

 Britain up to the end of the century and this delusion contributed 

 largely to the loss of many millions by the nation. Experiments 

 made at Brown Institution were held to sustain this, but not an 

 atom of evidence was furni,shed to show that the exposed animals 

 were susceptible ones. Diseased lungs kept for a year at 21° F. 

 proved infecting when inoculated (Laguerriere). 



Contagion through the air in the same stable was admitted 

 even by the English sceptics. It may be carried in this way for 

 forty yards, or if dried on dust or light materials to a great distance. 



Infection through food soiled by breath or nasal defiuxion is a 

 common cause. In our great swill stables during the prevalence 

 of the plague, it was notorious that the disease advanced rapidly 

 along the line of a feeding trough to the sixty or more animals 

 using it, and that the rapidity of the advance was determined 

 largely by the fact that the first animal was at the higher end of 

 the trough. If at the lower end there was no upward current to 

 •carry infection to the others. Open pastures where the .sick have 

 fed and watering troughs or ponds are common sources of infec- 

 tion. The permanence of infection in and around large cities is 

 largely due to the common pasturage by different herds in suc- 

 cession on the .same unfenced lots waiting to be purchased for 

 building. For this rea.son the plague always extended in .summer 

 when the cattle frequented these lots, and diminished in winter 

 when they were strictly confined to stables and yards. 



Mingliug of different herds on great unfenced areas has been 

 the main cause of the maintenance of the infection from time im- 

 memorial in the hills and forests of central Europe and on the 

 boundless Steppes of Europe and A.sia. This alone is chargeable 

 with the permanence of the affection, in spite of all efforts for its 

 extinction, in South Africa, Australia, Ta.smania and New 

 Zealand. 



Contagion carried by attendants, cattle dealers and even dogs, is 

 generally recognized, I have elsewhere quoted the case, in E. 

 Lothian, Scotland, in which the son of the steward, who was 

 cattleman on an infected farm, was the means of infecting first, his 

 father's cow, and later the whole of the stock on the place ; also 



