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 



