usually die or become badly stunted.

RABIES, HYDROPHOBIA.--Rabies is an infectious disease affecting the nervous
system, that is transmitted by the bite of a rabid animal and the
inoculation of the wound with the virus present in the saliva. It is
commonly considered a disease of dogs, but because of the disposition of
rabid dogs to bite other animals, rabies is common in domestic animals and
man.

Rabies is widely distributed, being most prevalent in the temperate zone,
and where the population is most dense. It has been excluded from
Australia, Tasmania and New Zealand by a rigid inspection and quarantine of
all imported dogs.

_The specific cause of rabies_ is probably a protozoan parasite (the Negri
bodies present in nerve-cells, Fig. 105). The germ spreads from the wounds
through the nerves and central nervous system. The disease-producing
organisms are present in great numbers in the nerve-tissue and saliva.

_The period of incubation_ varies from a few days to several months. It is
usually from ten to seventy days.

_The symptoms_ differ in the different species. There are two forms of the
disease: the _furious_ and the _dumb_. The former is more common.

[Illustration: FIG. 105.--Negri bodies in nerve-tissue.]

_In the dog, the symptoms may be divided into three stages_. The first, or
_melancholy stage_, usually lasts from twelve to forty-eight hours. The
animal's behavior is altered and it becomes sullen, irritable and nervous.