652 DISEASES CAUSED BY FILTRABLE VIRUS 



virus through 21 generations on artificial media, a fact which alone would 

 seem to prove that he had successfully cultivated it, even though his 

 "nucleated bodies" do not eventually turn out to be anything more 

 than cell degenerations. The possibility that he may have carried 

 original virus through 21 generations and that it has remained virulent 

 for about 100 days at 37.5 C. can not be excluded as yet, but seems 

 very remote. 



The Specific Therapy of Rabies. The treatment which is now pro- 

 phylactically applied to patients infected with or suspected of infection 

 with rabies has been but little altered either in principle or in technical 

 detail since it was first worked out by Pasteur. In principle it con- 

 sists of an active immunization with virus, attenuated by drying, admin- 

 istered during the long incubation period in doses of progressively 

 increasing virulence. 



By the repeated passage of street virus through rabbits, Pasteur 

 obtained a virus of maximum and approximately constant virulence 

 which he designated as virus fixe. By a series of painstaking experi- 

 ments he then ascertained that such virus fixe could be gradually at- 

 tenuated by drying over caustic potash at a temperature of about 25 

 C., the degree of attenuation varying directly with the time of drying. 

 Thus, while fresh virus fixe regularly caused death in rabbits after six to 

 seven days, the incubation time following the inoculation of dried virus 

 grew longer and longer as the time of drying was increased, until finally 

 virus dried for eight days was no longer regularly infectious and that 

 dried for twelve to fourteen days had completely .lost its virulence. 



The method of active immunization, which Pasteur used, consisted 

 in injecting, subcutaneously, virus of progressively increasing viru- 

 lence, beginning with that derived from cords dried for thirteen days 

 and gradually advancing to a strong virus. Thus the patient was im- 

 munized to a potent virus several weeks before the incubation time of 

 his own infection had elapsed. Pasteur successfully proved the efficacy 

 of his method upon dogs and finally upon human beings, the first 

 human case being that of a nine-year-old child Joseph Meister. 



TECHNIQUE OF RABIES THERAPY. The technique developed by 

 Pasteur is still, in the main, followed by those. who treat rabies to-day. 



I. As a preliminary, it is necessary to prepare or obtain virus fixe. 

 This may generally be procured from an established laboratory or may 

 be prepared independently by passing street virus through a series of 

 young rabbits (weighing from 700 to 1 ,000 gms.) . According to Hogyes, 1 



1 Hogyes, quoted from Kraus and Levaditi, "Handb.," etc., I. 



