40 The Lung Plague of Cattle. 



It should be added that hot climates and seasoua 

 abridge the period of latency; thus, the disisase T^ill de- 

 velop more rapidly in summer than in winter, and in the 

 south than in the north. Any febrile condition of the 

 system will also favor its rapid development ; therefore, 

 symptoms are often hastened by parturition, by heat, 

 (cestrum), and by other exciting conditions. 



Symptoms. 



These vary in different countries, latitudes, seasons, 

 altitudes, races of animals and individuals. They are 

 caeteris paribus, more severe in hot latitudes, countries 

 and seasons, than in the cold ; in the higher altitudes they 

 are milder than on the plains ; in certain small or dwarfed 

 animals, with a spare habit of body, like Brittanies, they 

 appear to be less violent than in the large, phlegmatic, 

 heavy-milking, or obese short-horn, Ayrshires and Dutch ; 

 a newly infected race or cattle in a newly infected coun- 

 try suffer much more severely than those of a land where 

 the plague has prevailed for ages ; and finally certain in- 

 divduals, without any appreciable cause, have the disease 

 in a much more violent form than others which stand by 

 them in precisely the same conditions. 



Sometimes the disease shows itself abruptly with 

 great violence and without any appreciable premonitory 

 symptoms, resembling in this the most acute type of or- 

 dinary broncho-pneumonia. This, however, is mostly in 

 connection with some actively exciting cause, such as 

 exposure to inclement weather, parturition, overstock- 

 ing with milk, heat, etc. 



Far more commonly the symptoms come on most in- 

 sidiously, and for a time are the opposite of alarming. 

 For some days, and quite frequently for a fortnight, a 

 month or more, a slight cough is heard at rare intervals. 

 It may be heard Only when the animal first rises, when H 

 leaves the stable or when it drinks cold water, and hence 



