Period of Latency. 157 
The animal often wags its tail in answer to soothing words 
immediately before or after a dangerous paroxysm of mania. 
It will usually drink greedily—even its own urine—until 
the condition of inflammation renders the effort painful, 
when the sight of fluid may bring on a violent spasm or 
convulsion. Hence the term “hydrophobia” is misleading 
in most cases; and even an excessive desire to drink should 
raise no presumption of security. Neither is the presence 
of the viscid saliva at all a constant symptom. 
The aspect of a mad dog, wandering in melancholy mood 
through the streets, in a steady jog trot, with hanging 
jaw, has been described by Youatt. He is not usually dis- 
posed to go out of his way to attack, but will bite dogs 
or other animals, or even inanimate objects, such as posts 
or vehicles, met with on the way. It is generally a sud- 
den snap, and the sufferer passes on his way. Deliberate 
onslaughts have occasionally occurred, though rarely. Such 
a dog should be quietly avoided—excitement, noise, and 
screaming are calculated to provoke an attack. 
Authorities differ as to the term of latency or incubation. 
In one case, apparently well authenticated, rabies supervened 
on the third day after the bite was inflicted. The virus 
may, however, be latent apparently for as long a period as 
twelve months, or more. The period of incubation may vary 
from weeks to months in two animals bitten by the same 
rabid dog. Eight or ten days seems to be about the utmost 
limit of the life of a rabid dog, the average being five or 
six days, but death may take place in a shorter time. 
The instances of very prolonged latency of the disease 
in both man and the dog are open to the suspicion that 
a second unobserved inoculation may have taken place. How- 
ever carefully a dog may have been watched after having 
received a bite, he is obviously liable to have incurred a 
second of so slight a character as to pass unnoticed. Simi- 
larly, during the period (of many years) in which the disease 
has been asserted to be occasionally latent in man, it may 
