CONTAGIOUS DISEASES OP DOMESTICATED ANIMALS. 441 



Lung plague (pleuro-pneumonia) confines its ravages entirely to tlie 

 bovine genus, and no race, l)reed, or age is exempt from its attacks. 

 Sex gives no ijumunity ; bulls suffer as much as cows 5 and oxen and 

 calves, if equally exi^osed, furnish no fewer victims than bulls and cows. 



As in rinderpest, measles, scarlatina, and the different forms of vari- 

 ola, an animal once afflicted with lung plagTie is usually exempt or im- 

 l^ervious to a second attack. Only occasional instances are given vv^here 

 an animal has suffered from a second attack. The losses caused by the 

 plague ranges all the way from 2 to 03 per cent, of all the animals in 

 the country or locality in which it prevails, the losses varying according 

 to climate, surroundings, condition of stock, &c. 



The period of latency, that is, the time that elapses between the re- 

 ceiving of the germs into the system and the manifestation of the first 

 symptoms of the disease, varies greatly. Veterinarians differ as to their 

 experience and statements, and set this period at from five days to three 

 months. Dr. Law has seen cases in which cattle have passed three or 

 four months after the purchase in poor health, yet without cough or any 

 other diagnostic symptom, and at the end of that time have shown aU 

 the symptoms of the lung plague. It is this long period of latency that 

 renders the disease so dangerous. An infected animal may be carried 

 half way round the world before the symptoms of the malady become 

 suflficiently violent to attract attention, and yet all this time it may have 

 been scattering the seeds of the disease far and wdde. The average 

 period in inoculated cases is nine days, though it may appear as early 

 as the fifth, or it may be delayed till the thirtieth or fortieth day. In 

 the experimental transmission of the disease by cohabitation, under the 

 French commission, a cough (the earliest symptom) appeared from the 

 sixth to the thirty-second day, and sometimes continued for months, 

 though no acute disease supervened. Hot climates and seasons abridge 

 the period of latency, as the disease has been found to develop more 

 rapidly in summer than in winter, and in the South than in the li^orth. 

 A febrile condition of the system also favors its rapid development. Of 

 the symptoms of the disease, Dr. Law says : 



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 cert.aiu small or dwarfed animals, with a spare habit of body, like Brittauies, they 

 appear to be less violent than in the large, phlegmatic, heavy-milking, or obese short- 

 horn Ayrshires and Dutch. A newly-infected race of cattle in a newly-infected coun- 

 try sufi'er much more severely than those of a land where the plague has prevailed 

 for ages; and finally certain individuals, 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 ordinary 

 broiicho-pneumonia. This, however, is mostly in connection with some actively 

 exciting cause, such as exposure to inclement weather, parturition, overstocking with 

 milk, heat, &c. 



Far more commonly the symptoms come on most insidiously, and for a time are the 

 oi»posite of alarming. For some days, and quite frequently for a fortnight, a month 

 or _more,^ a slight cough i.s heard at rare intervals. It may be heard only when the 

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

 attracts little or no attention. The cough is usually small, weak, short and husky, 

 but somewhat painful and attended by some arching of tlie back, an extension of the 

 head upon the neck, and protrusion of the tongue. This may continue for weeks 

 withoiit any noticeable "deviation from the natural temperature, pulse, or breathing, 

 and without any impairment of appetite, rumination, or coat. The lungs are as reso- 

 nant to percussion as in health, and auscultation detects slight changes only, perhaps 

 an unduly loud blowing sound behind the middle of the shoulder, or more commonly 

 8a occasional slight mucus rattle, or a transient wheeze. In some cases the disease 



