On Rabies. 



69 



Pasteur states (' Comptes Rendus,' vol. 101, 1885, p. 770) that the 

 progressive modification of virulence in cords thus preserved is 

 attested by the increasing length of the incubation period in rabbits 

 inoculated intracranially with them, and that the duration of this 

 period increases regularly with those dried up to seven days, but 

 that from and after that period they are not virulent. 



I have myself in several experiments invariably found the latter 

 part of this statement correct, and that cords dried for seven days or 

 more are absolutely inert, as are frequently those of six and of five 

 days. 



But I have not by any means found the progressive prolongation 

 of the incubation period, with cords dried for a shorter time, as regu- 

 lar as he records, but on the contrary I have found it usually the same 

 as with fresh cords, unaltered up to and including the fourth day ; in 

 one case only when inoculating from one dried four days, did the first 

 symptoms of infection, which were not well marked, appear to be 

 deferred till between the ninth and tenth day, the animal dying on 

 the thirteenth. 



As in cords thus treated the virus certainly becomes altogether 

 extinguished, teste Pasteur, and, as I have myself found, somewhat 

 suddenly, by the seventh day, it appears doubtful what benefit can 

 result by inoculating subcutaneously with those of a longer period, 

 with the object of prophylaxis. 



The preservation of cords by this method, in an atmosphere kept 

 perfectly dry by caustic potash, entirely prevents the occurrence of 

 microbial putrefaction ; its absence is plainly evinced by no fetor being 

 perceptible in them, as saprophytes are unable to develop in a per- 

 fectly dry atmosphere, as well as in one of carbonic acid. 



I have too examined with the microscope portions of cords thus 

 preserved for different periods, but have never recognised any micro- 

 phytes ; if they had been present in any numbers they could not have 

 escaped observation. 



To prove their absence certainly, I took part of a cord preserved as 

 described for five days, and snipping the outer surface, which was 

 dry and firm, I plunged a sterilised platinum needle into its substance, 

 which was moist and viscid, adhering in very appreciable quantities 

 to the needle. With this I inoculated a tube of agar-agar bouillon 

 peptone, and performed this operation three times ; the tubes thus 

 inoculated were placed in the incubator at 38° 0., no organisms de- 

 veloped, and their contents remained altogether unchanged until 

 they ultimately dried up, showing the total absence of septic microbes. 



I may add that in a room of any ordinary laboratory it would, I 

 believe, be practically impossible to remove any number of cords and 

 transfer them to the requisite vessels, without some germs of septic 

 organisms falling upon them during the operation ; and that con- 



