RABIES 533 



the dura mater of the brain. It may be produced almost as certainly 

 when the infection 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 peripheral 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 sur- 

 faces from which this has occurred. The rapidity with which the virus 

 is diffused through the body from the point of inoculation in the tissues 

 seems to vary according to the location of the wound, but it is always 

 comparatively slow. It has been found that rabbits, when etherized 

 and then presented to a mad dog to be bitten on the fur, escape the 

 disease in a very large proportion of cases, although the teeth may have 

 passed well through the skin; if, on the other hand, the part presented 

 to the rabid dog be shaved before it is bitten, the bitten animals con- 

 tract rabies in a much larger proportion of cases. So in man, in many 

 cases the rabic virus may be cleaned from the teeth by the clothing 

 which covers the bitten part before they come in contact with the skin. 

 From what has been said it is evident also that when the skin is thick 

 and the nerves few a small quantity of virus may find its way into a 

 wound, but not penetrate into the nerves, and thus the person bitten 

 by a rabid animal may escape without any ill effects beyond those due 

 to a lacerated wound. This will explain the fact that only about 16 

 per cent, of the cases bitten by rabid animals appear to contract hydro- 

 phobia. 



Preventive Inoculation against Rabies. The old treatment of rabies 

 consisted simply in encouraging bleeding from the wound, or in first 

 excising the wound and then encouraging bleeding by means of liga- 

 tures, warm bathing, cupping-glasses, etc.; the raw surface was then 

 freely cauterized with caustic potash, nitric acid, or the actual cautery. 

 It is doubtful whether the disease ever manifests itself after such heroic 

 treatment if the wound be small; but when the wounds were numerous 

 or extensive the mortality from it was still high. As it was often impos- 

 sible to apply cauterization to the wound rapidly or deeply enough to 

 ensure complete destruction of the virus, Pasteur and others were 

 led to study the disease experimentally in animals, with the hope of 

 finding some means of immunization or even cure through bacterio- 

 logical technique; these investigations finally resulted in the discovery 

 of methods of preventive inoculation applicable to man. 



Immunization against rabies may be effected in several different 

 ways. Pasteur's treatment is based upon the fact that rabic virus may 

 be attenuated or intensified for any animal at will. He first observed 

 that the tissues and fluids taken from rabid animals varied considerably 

 in their virulence. Then he showed that the virus taken from similar 



