Prophylaxis ' 373 



rabbit from twenty to thirty times, a maximum virulence is attained 

 and the virus is said to be " fixed." Pasteur found that the virulence 

 of the nervous tissue was diminished by inspissation, by drying under 

 aseptic precautions in a sterile jar over calcium chloride. There is 

 some doubt whether this results in actual diminution in the virulence 

 of the organisms as Pasteur thought, or whether the virulence is 

 diminished by dilution, i.e., by effecting the destruction of many 

 of the organisms. There seems to be no means of determining this 

 at present. The diminution of virulence is in proportion to the length 

 of time the nervous tissue is dried. 



Prophylaxis. — To prevent rabies, means must be devised for 

 preventing dog-bites. In an island community like England, rabies 

 may be successfully eliminated by destroying all animals suspected 

 of having the disease, muzzling the dogs for a time, and denying 

 admission to new dogs until they have spent a long enough period 

 in quarantine to exclude the possibility of their being infected with 

 the disease. 



Upon continents it seems unlikely that rabies can ever be com- 

 pletely eradicated as it is not only a disease of dogs, but also of 

 wolves, foxes, skunks and other wild animals by which dogs may be 

 bitten. 



However, it is the dog that is the common distributor and to 

 which attention must be directed. 



All rabid animals should at once be killed, and all others known 

 to have been bitten by them also killed so soon as the diagnosis of 

 rabies in the first animal is confirmed. If the bitten animals cannot 

 for any reason be kUled, they should be carefully confined until the 

 incubation period is long past. All stray dogs and cats should be 

 destroyed because not being under any observation, their condition 

 is not known. Dogs in general should be muzzled when abroad. 



Immunity to rabies may be brought about in human beings by 

 the method of active immunization given below, but as rabies is a 

 somewhat rare disease of human beings, it does not seem worth 

 while to advise immunization except when there is some particular 

 danger of its occurrence. Such danger obtains when human beings 

 have been attacked and bitten by rabid animals or by dogs running 

 at large, whose health is a matter of doubt. Recovery from rabies 

 in human beings is practically unknown. Any individual, therefore, 

 that is bitten under suspicious circumstances may be in danger of 

 developing an almost certainly fatal malady. This is not to be con- 

 strued to mean that every person bitten by a certainly rabid dog 

 must necessarily contract rabies, for there are accidents and cir- 

 cumstances attending the transmission of diseases of infectious na- 

 ture, but whether certain or not, the danger of rabies is great in 

 such cases and they ought to receive immediate care and attention. 

 Many content themselves with an attempted destruction of the 

 introduced virus by applying the actual cautery, or caustics, or 



