26 KENNEL DISEASES. 
are produced by special or specific causes. In fact, that the cause is specific is 
to be inferred if the disease it gives rise to can be transmitted from one dog to 
another, or, in other words, is “catching,” and the special germ or poison develops 
that same malady always, and no other. 
Infectious diseases are known, or at least confidently believed, to originate 
through the infection of the system with certain peculiar poisonous matters, and 
the same are mainly distinguished from ordinary poisons by their ability to repro- 
duce themselves, under favorable conditions, to an unlimited extent. The pecu- 
liarity of this class of diseases is their specificness, which is evident in the fact 
that a given kind of disease is solely due to a given kind of morbid agent or cause. 
In this respect they are essentially different from diseases propagated by ordinary 
causes. Of the latter class exposure to cold is an illustration, and that may oc- 
casion different affections in different subjects. Thus, in one dog it may give rise 
to bronchitis, and in another to colic or diarrhcea. On the other hand, infection 
from a dog suffering from distemper primarily produces that disease, and never 
any other. 
Strictly defined, contagion is the conveyance of disease by touch or contact. 
But some disorders, not all, however, which may be transmitted by actual touch, 
are yet capable of passing a short distance through the air and doing their evil 
work. Infectious diseases are communicable and contagious. They are not all 
alike propagated by immediate, direct, or personal contact. In some such dis- 
eases the contagious element is fixed close to the body affected, or is attached 
to objects once in contact with the body. In some others the poison which 
causes them is more volatile; it is dissipated from the body, and disseminated to 
a greater distance through the air. In still others it is the discharges from the 
intestines which chiefly convey the contagion, to finally infect the soil, and 
through that or sewage canals, by filtration, to great distances, the drinking- 
water. To breathe infected air or drink infected water, though distant from 
the focus of infection, suffices to engender some maladies. The contagion of 
others, of which diphtheria is an example, must be lodged upon the mucous 
membrane; while that of rabies, the virus of venomous animals, and of a few 
other maladies, to produce infection must be inoculated into the very blood 
itself. 
Certain infectious diseases are termed ,miasmatic. Miasm, in its original 
and broadest sense, is the name of any material contained in the air that can 
produce disease. The term is now used in a far narrower sense, and in contra- 
distinction with the term contagion. The latter being accepted to be a specific 
excitant of disease which originates in the organism suffering from the specific 
disease, miasm is used to designate a specific excitant of disease which propa- 
gates itself outside of and entirely separable from a previously diseased organ- 
ism. Contagion can be conveyed by contact from a diseased dog to a sound 
one, produce the disease in him, and then reproduce itself. Miasm originates 
