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Il. WHAT IS THE DISEASE ? 
An Epizootic_—The lung plague is a fever attacking cattle, of a purely con- 
tagious character, spreading from farm to farm and country to country as an 
epizootic, and exclusively in the lines of communication established by the eat- 
tle trade. It never originates spontaneously. All domestic cattle, whether 
high or low bred, are alike subject to its ravages, without distinction even as to 
sex, age, or condition. Milch cattle have been destroyed in by far the largest 
numbers, inasmuch as the facilities for communication to this class of cattle 
have been greatest. The lung plague is, in my opinion, a disease of the greatest 
antiquity, and during the past century numerous reports from all parts of Ku- 
rope, and wherever it has been transported, indicate that in all climes and at all 
seasons it presents well defined and immutable characteristics as to its insidious 
origin and propagation, symptoms, fatality, and incurability. 
The poison, or virus.—The poison of the lung plague is dep osited in varying 
amounts, but usually to the extent of many pounds weight, and not unfrequently 
as high as half a hundred weight, in the lung tissues, cavities of the chest, and 
air passages. The same poison may be reproduced in any part of an ox’s sys- 
tem as the result of inoculation, and its development is usually co-extensive 
with the mass of areolar or connective tissue—the tissue that binds the skin to 
the tissues beneath and all the tissues to each other—into which it is introduced 
on the point of a needle, or by injection. The deposit is limited in parts sparsely 
supplied with this connective tissue, or where the parts are firmly enveloped by 
skin, as towards the end of the tail or tip of the ears. But occasionally even 
the greatest care in introducing a small quantity of virus on the surface of the. 
skin without penetrating the more open textures below, results in extensive 
swellings due to.a deposit which is identical with that. occurring in ordinary 
cases of this lung complaint. 
Tests for the poison.—Attempts have been made to discover microscopical or 
chemical tests for the poison. The only test is the physiological one, viz: the 
development of the same poison capable of indefinite propagation among cattle. 
It is only recognizable in the diseased animal, and every ox, bull, cow, or calf 
showing signs of such contamination should be dealt with as a bottle of poison, 
a carrier of pestilence, breathing forth, even when its pulse is quiet, nutrition 
unimpaired, and it is convalescent, quite enough of the same poison to kill hun- 
dreds and thousands of its kind. 
Infection —The malady has been recognized as infectious, that is to say, the 
poison is diffused through the air by the breath of sick cattle. The poison is 
not gaseous or volatile. The solid elements in its composition like the solid 
germs of decay, or the delicate seeds of plants are carried by atmospheric cur- 
rents: Myriads impinge on inert matter, but any passing into the air passages 
with the air breathed by cattle produce a local change, which is at first slow 
and unobserved, usually followed by a general fever, and in any case attended 
by the expulsion of abundant volumes of a similiar material. 
Inoculated disease not infectious.—Some years’ experience and a large num- 
ber of observations in various parts of Europe would indicate that when the 
virus is developed in or beneath the skin it remains in the system of the inocu- 
lated animal, the lungs are not affected, and there is no communication of the 
disorder except by inoculation. It may safely be accepted that the inocu- 
lated disease is,.as a rule, not infectious. 
The virus of lung plague, when transmitted through the atmosphere, can 
alone be preserved and transported in the breathing organs of susceptible cattle, 
which reproduce it. It is not carried, so far as we know, by other animals. 
Incubation of the poison—It may lie latent for a considerable time. Usually 
the period required for inducing obvious symptoms of sickness extends over 30 
