238 DISEASES OF TB UE INFECTION. 



rabid brain loses its infectious virulence only when that part has 

 become partially decomposed, say after four or five days; while 

 it remains virulent in air-tight tubes or in moistened carbolic 

 gauze. Neustube found that the brain of a rabid dog retained its 

 virulent properties when kerpt under a slightly elevated tempera- 

 ture for ten or twelve days. Mergel found the virulence as strong 

 as ever in the putrid brain of a rabid wolf fourteen days after the 

 animal had been killed. Galtier noticed the same conditions in the 

 decayed brain-substance of a rabid dog, when kept under a low 

 temperature (12° Celsius). An affected brain was not rendered 

 harmless even when exposed for three weeks, but its virulence was 

 attenuated when kept some time at 61° Celsius. Blumberg found 

 that an affected brain is rendered harmless when it has undergone 

 a freezing process of 20° to 30°. Galtier was able to destroy the 

 virulence of affected cerebral matter in four to twenty days by 

 placing it upon plates and allowing it to become dry. Tizzoni 

 foimd that radium destroyed the virus. Saliva and blood are much 

 less resistant than brain-matter. Both substances, as a rule, lose 

 their harmful property twenty-four hours after leaving the animal. 



As a rule, it is necessary to make a natural or artificial inocula- 

 tion in order to obtain any successful transmission of the rabid 

 poison, as no infection will take place if the inoculation is simply 

 rubbed on the cutaneous or mucous membranes. The most com- 

 mon method, of course, is the bite of the rabid animals; more 

 rarely, licking of a wound. In many cases the bite may not be 

 severe enough to cause its development in dogs or in man. Deep 

 bites, however, are certainly the most dangerous, especially when 

 made on Ihe unprotected parts of the body (hands and face in man). 

 Wounds which bleed much are less dangerous, as the poison may 

 be washed out of the wound by the flowing blood. Bites of dogs 

 which have bitten numerous others are less dangerous than the 

 first or second bite made by a rabid animal. 



Infectious wounds which were made by biting or inoculation, 

 according to Hertwig's observations, showed only 37 per cent, of 

 positive results, and Eenault's 67 per cent. Of 137 animals 

 which were bitten by rabid dogs under observation for the last 

 five years at the Veterinary College of Berlin, six only ultimately 

 developed the disease. Zundel finds that about 25 per cent, of 

 inoculated animals become affected, while Haubner found 40 per 



