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to 40 days, but during this time it is producing local effects, as proved by the 
results of inoculation, which are obvious nine days after the operation. 
Latent effccts—It has been supposed that an animal may be infected and 
remain in health for several months. This is an error. The virus sometimes 
induces local changes without outward manifestations such as usually arrest 
attention. Its development under some circumstances is slow, and the affected 
animal or animals beginning later than usual to discharge poison into the air 
retain the faculty of communicating the disease until an almost complete recovery. 
The lung plague has therefore a latent stage in all cases, and in some it assumes 
what pathologists term a latent type, whereby its earliest attacks pass unnoticed. 
Preservation of the virus—The most certain means of preserving the virus 
for artificial propagation is by maintaining, as one gentleman has especially 
done near Glasgow, sick cattle, infected in succession. 
By transmission—aAn animal that has once had the disease is incapable of 
reproducing the poison, and although there are a few isolated cases of tardy 
relapse which would seem to indicate that a second attack of the malady may 
occur in an animal, it is almost universally admitted that, as in the case of other 
true epizootics, the lung plague attacks an ox but once in its lifetime. 
In botiles.—The owners of cattle, and especially dairymen, have adopted the 
plan of preserving the virus for periodical inoculations in common bottles pro- 
vided with a cork. The matter thus kept decomposes, but retains’ for many 
months the power of producing the usual and, generally aggravated, results 
after inoculation. This is a fact well worthy of careful inquiry and most sug- 
gestive to the many now engaged in tracing the history of animal poisons. 
With glycerine —It was proposed, first in Australia, to mix the lymph from 
the lungs with glycerine. After many trials I had to abandon this plan, inas- 
much as the glycerine impaired and ultimately destroyed the virus. 
Desiccation—The lymph obtained by draining the diseased lung may be 
placed between strips of glass and dried; as vaccine lymph does under similar 
circumstances, it retains its power for many months. 
Destruction of the virus.—Preparations of chlorine, iodine, bromine, sulphur- 
ous acid, carbolie acid, sulphate of iron, &c., destroy the virus and render it 
inert. 
Ill, WHAT CIRCUMSTANCES FAVOR THE TRANSMISSION AND REPRODUCTION OF 
THE LUNG PLAGUE POISON. 
Contact of sick and healthy—Approach of sick and healthy susceptible cat- 
tle is the fundamental and essential cause of contagious pleuro-pneumonia. 
Cohabitation not necessary, but the most common cause.—Transmissivn of the 
disease does not require cohabitation. ‘The most common means whereby the 
virus spreads is undoubtedly by sick or convalescent cattle being admitted into 
sheds, yards, or pastures, and retained in close proximity with other animals; 
but a variable degree of susceptibility is noticed from the animals first seized 
being often at the most remote’ part of a stable into which a sick beast has been 
introduced. There is some uncertainty in observations of this kind, from the 
fact, already stated, that some cases are latent and symptoms being very imper- 
fectly observed by farmers and the usual attendants on stock. 
Exposures in the open air, communication on railroads—The communica- 
tion of the disease in many European cities is due to the exposure of sick cattle 
for sale in public markets; the driving of sick cattle on roads; the transporta- 
tion of diseased animals in railway cars in which, or in cars adjoining which, are 
healthy cattle. ‘The ready propagation of the virus under these circumstances 
is generally admitted, and an inquiry into many outbreaks shows that when the 
disease enters among cattle in the fields it is often more rapidly fatal, less fre- 
quently latent, and better calculated to alarm stock owners than the more insidious 
