ted by a bite
and by the introduction of a virus contained in the saliva of an
affected animal. It may, however, be transmitted in other ways. It is
characterized by symptoms of aberration of the nervous system and
invariably terminates fatally. It is accompanied with lesions,
inflammation, and degeneration in the central nervous system. It is a
disease that is most common in the dog, but is transmitted to the horse,
either from dogs or from any other animal affected with it. (See also
remarks on page 244.) As a disease of the horse it is invariably the
result of the bite of a rabid animal, usually a dog.

Perhaps no disease in medicine has been the object of more controversy
than rabies. Certain medical men of prominence have even doubted its
existence, and many others have claimed for it a spontaneous origin. The
experience of ages, however, has shown that contagion can be proved in
the great majority of cases, and, by analogy with other contagious
diseases, we may only believe that the development of one case requires
the preexistence of a case from which the virus has been transmitted.
Pasteur has further added to our knowledge of the disease by showing
that a virus capable of cultivation exists in the nervous system,
especially in the lower part of the brain (medulla oblongata) and in the
anterior part of the spinal column. He has further shown that that
portion of the nervous system which contains the virus, the exact nature
of which has not yet been demonstrated, will retain it for a very long
time if kept at a very low temperature or if left surrounded by
carbolic acid; but if the nerve matter, which is virulent at first, is
exposed to the air and is kept from putrefaction by substances which
will absorb the surrounding moisture, it will gradually lose its
virulence and become inoffensive in about fifteen days. He has also
further shown that the action of a weak virus on an animal will prevent
the development of a stronger virus, and from this he has formulated his
method of prophylactic treatment. This treatment consists in the
successive inoculation of portions of the nerve matter containing the
virus from a rabid animal which has been exposed to the atmosphere for
thirteen days, ten days, seven days, and four days, until the virulent
matter which will produce rabies in any unprotected animal can be
inoculated with impunity. A curious result of the experiments of Pasteur
is that an animal which has first been