236 



NATURE 



{July 7, 1887 



has been slated, rabbits inoculated by M. Pasteur's virus rarely 

 show symptoms during more than three days before death, 

 whereas the rabbits bitten by rabid dogs from the streets often 

 live for a week after the appearance of the first symptoms. 



The post-mortem appearances in the rabbits dying after 

 having been bitten by rabid dogs of the streets were the same as 

 those already described in rabbits inoculated with the virus from 

 M. Pasteur's rabbits. 



In the case of rabbits inoculated by trephining with the virus 

 from animals dying of rabies of the streets, the incubation period 

 was from 14 to 21 days. In all cases the symptoms were 

 similar to those produced by M. Pasteur's virus, and those of 

 rabbits bitten by rabid dogs from the streets ; but in the pro- 

 longation of the disease approached more closely in character to 

 the latter. 



The results of these experiments confirm several of the chief 

 observations made by M. Pasteur ; especially — 



(i) That the virus of rabies may certainly be obtained from 

 the spinal cords of rabbits and other animals that have died of 

 that disease. 



(2) That, thus obtained, the virus may be transmitted by 

 inoculation through a succession of animals, without any essential 

 alteration in the nature, though there may be some modifications 

 of the form, of the disease produced by it. 



(3) That, in transmission through rabbits, the disease is ren- 

 dered more intense ; both the period of incubation, and the 

 duration of life after the appearance of symptoms of infection, 

 being shortened. 



(4) That, in different cases, the disease may be manifested 

 either in the form called dumb or paralytic rabies which is usual 

 in rabbits ; or in the furious form usual in dogs ; or in forms 

 intermediate between, or combining, both of these, but that in 

 all it is true rabies. 



(5) That the period of incubation and the intensity of the 

 symptoms may vary according to the method in which the virus 

 is introduced, the age and strength of the animal, and some 

 other circumstances ; but, however variable in its intensity, the 

 essential characters of the disease are still maintained. 



The certainty that the virus of rabies can thus be transmitted 

 without essential change made it desirable, in the next place, to 

 ascertain whether, as M. Pasteur states, it can be so attenuated 

 that it may be inoculated witliout risk to life, and whether 

 animals thus inoculated are thus made safe from rabies. The 

 methods for this protective inoculation which M. Pasteur has 

 employed are described. 



To test them, six dogs were " protected " by injecting sub- 

 cutaneou-^ly the emulsions of spinal cords of rabbits whicli had 

 died of rabies ; beginning with that of a cord which had been 

 dried for 14 days, and, on each following day, using that of a 

 cord which had been dried for one day less, till at last that from 

 a fresh cord was used. 



None of these dogs suffered from the injections ; and when 

 they were completed, the six dogs thus "protected," and two 

 others unprotected, and ?ome rabbits unprotected, were made 

 insensible with ether, and were then bitten by rabid dogs, or by 

 a rabid cat, on an exposed part. 



A "protected" dog, No. 1, was bitten on July 8, 1886, by 

 a dog which was paralytically rabid. It remains perfectly well. 

 An "unprotected" dog. No. i, was bitten a few minutes 

 afterwards by the same rabid dog, and died paralytically rabid. 



A "protected" dog, No. 2, was bitten on November 6, 

 1886, by a dog which was furiously rabid ; it rernains well. At 

 the same time, four " unprotected " rabbits were bitten by the 

 same rabid dog, and of these two died of rabies in the usual form 

 [i.e. 50 per cent, of animals bitten). 



The same results followed with the " protected" dog. No. 3, 

 and the "unprotected" rabbits, bitten at the same time. The 

 dog still lives, the rabbits died of rabies. 



The "protected" dogs, Nos. 4 and 5, were bitten on 

 January 20, 1887, by a furiously rabid dog ; and on the same 

 day the " unprotected " dog. No. 2, and three "unprotected" 

 rabbits were bitten by the same dog. The " protected " dogs 

 remain well ; the "unprotected" dog and two rabbits died with 

 rabies (i.e. 75 per cent, of the animals bitten.) 



The "protected" dog, No. 6, was bitten on three different 

 occasions by a furiously rabid cat on September 7, 1886 ; by a 

 furiously rabid dog on October 7, 1886 ; and by another 

 furious '.rabid dog on November 6, 1886. It died ten weeks 

 after being bitten for the third time, but not of rabies. It had 

 been suffering with diffuse eczema during the whole of the time 



that it was under observation, and it died of this. At the post- 

 mortem examination, no indication of rabies was found ; and 

 two rabbits, inoculated by trephining with the crushed spinai 

 cord, showed no sign of rabies, either during life or, when thej 

 were killed several months afterwards, in any appearance aftei 

 death. It was thus made certain that the dog was not rabid. 



Thus, all the experiments performed by Mr. Horsley have 

 confirmed those of M. Pasteur, and the experiments lasi 

 described have shown that animals may be protected fron 

 rabies by inoculations with material derived from spinal cordi 

 prepared after M. Pasteur's method. The protection may b( 

 deemed somewhat similar to that given by the inoculation foi 

 anthrax, or by vaccination for small-pox, though the theory o: 

 the method of inoculation devised by M. Pasteur is very differeni 

 from that upon which vaccination for small-pox and inoculatioi 

 for anthrax is based. The further step, the prevention of rabie; 

 or hydrophobia in animals or in persons into whom the viru: 

 has already been introduced by bites or otherwise, is considerec 

 in the body of the Report. 



In the course of his experiments, Mr. Horsley observed man; 

 interesting facts concerning the modification of the action of th( 

 virus according to the method of its inoculation, and the condi 

 tion of the animal inoculated ; but he found nothing to justify i 

 belief that any animal not inoculated is insusceptible of rabies 

 or that the disease ever arises spontaneously.'^ 



Coincidently with these experiments, some were made b; 

 Mr. Dowdeswell for the purpose of ascertaining whether an; 

 drugs can protect an animal from rabies. Their result is re 

 corded in a paper read before the Royal Society, and may bi 

 summed up in the statement that rabies can neither be pre 

 vented nor influenced in its course, unless it be for the worse 

 by any of the drugs that were employed, including allyl alcohol 

 atropine, benzoate of soda, chloral, cocaine, curare, iodin* 

 (dissolved in iodide of potassium), mercuric perchloride, quinine 

 salol, strychnine, urethane. 



M. Pasteur's Methods of Preventive Inoculation.^ 



M. Pasteur believes that the virus of rabies is a living micro 

 organism, and that, like some others, it produces in the tissue 

 it invades an excretory substance by which, when present ii 

 sufficient quantity, its own development and increase ar 

 checked, as are those of the yeast ferment by the alcohol pro 

 duced in the vinous fermentation. In accordance with thi 

 theory, he thinks that the spinal cords of animals that have die( 

 of rabies contain both the virus and this excretoiy substanc 

 which, practically, may be deemed its antidote. He believe 

 therefore that by injections of an emulsion from such spina 

 cords into the systems of animals bitten or inoculated with th 

 virus of rabies, the antidote may be able, during the period c 

 incubation, to arrest and prevent the fatal influence of the virus 

 But, in order to avoid the possibility of injecting a still potei] 

 virus, M. Pasteur holds that the virus in the spinal cord mus 

 be weakened by drying the cord in a i^ure and dry atmospher 

 at a temperature of 20° C. ; in which drying the efficiency of th 

 antidote may be reduced to a much less extent than the potenc 

 of the virus. By such drying this potency may be so reduce 

 that an emulsion of the dried spinal cord may be injected witl 

 out any risk of producing rabies : and this risk is in no measur 

 increased by the daily injections of emulsions from cords drie 

 during a gradually less number of days, and which, though mor 

 virulent than those first used, still contain a larger proportion ( 

 the antidote than of the virus. 



In accordance with this theory, the method of the preventi\ 

 injections first used by M. Pasteur was adjusted in the followin 

 manner : — 



In consequence of some deaths among those who had bee 

 thus treated, M. Pasteur deemed it necessary, in cases of vei 

 severe bites and of persons bitten long before the treatmer 



' The minuter facts connected with all these experiments will soon I 

 communicaled to one of the scientific Societies. 



'^ As derived from the observations made by the Committee, and from 

 full description supplied by Prof. Dr. Grancher, April 11, 1887. 



