DISEASES FROM MICRO-ORGANISMS. 
129 
vation for sixteen days. During the illness the dis¬ 
charges from the mouth, nose and intestines should be 
disinfected. The quarantine must be maintained until 
the skin is entirely free from crusts and scales. 
The methods and principles of immunization to 
smallpox have been described under the subject of 
immunity. 
Chicken-Pox, or Varicella. 
This is an acute infectious disease of children. It 
is spread in the same manner as smallpox, but to 
prevent its spreading the precautions need not be so 
rigidly enforced because it is not so serious an infec¬ 
tion. The patient is kept from contact with other 
children, and after the recovery the room should be 
disinfected. 
Rabies, or Hydrophobia. 
Rabies is a disease common among animals, par¬ 
ticularly dogs, although cats, cattle, and horses may 
be infected. It is transmitted from one animal to 
another, and to man through the saliva from the bites 
of rabid animals. The poison acts upon the tissue of 
the brain and spinal cord, being carried there along the 
nerve trunks. The incubation period is usually from 
forty to sixty days. 
In animals the disease begins with a stage of 
excitement and restlessness, followed by depression, 
difficulty in swallowing, and paralysis. In man there 
is first headache and depression, later difficulty in swal- 
