RABIES. 661 
mined by three factors: (1) The quantity of the rabic 
virus introduced; (2) the point of inoculation; (3) the 
strength of the virus as determined by the kind of ani- 
mal which affords the cultivation ground for the growth 
of the hypothetical organism. It is a matter of com~- 
mon observation of hydrophobia in man that slight 
wounds of the skin, of the limbs, and of the back are 
often followed by the disease after an extremely long 
period of incubation; while in lacerated wounds of the 
_ tips of the fingers, where small nerves are numerous or 
where the muscles and nerve-trunks are reached, or in 
lacerated wounds of the face, where there is a similar 
abundance of nerves, the period of incubation is usually 
much shorter and the disease generally much more 
rapid. Experimental infection in animals is produced 
with the greatest certainty when the material from the 
rabic nerve-centre (the spinal cord or bulb) of a dog, 
or of a human being who dies of rabies, is injected into 
the dura mater of the brain. It may be produced almost 
as certainly when the injection is made into the anterior 
chamber of the eye or into the greater nerve-trunks. 
Intravenous injection is usually followed by positive 
results in small animals, but the larger animals do not 
succumb to this mode of inoculation. Subcutaneous 
inoculation in animals is uncertain, because the periph- 
eral nerves are not always injured; but injection directly 
into a mass of muscle, especially into parts which are 
rich in nerves, almost invariably produces the disease. 
Absorption of the rabic poison, even from a healthy 
mucous surface, has been said to have taken place; 
and the conjunctiva, the nasal and genital mucous 
membranes, and the digestive tract have been noted as 
unabraded surfaces from which this has occurred. The 
