Aug. ist, 1887.] 



SCIENTIFIC NE\VS. 



m 



easily rubbed down, the water is brilliantly blue ; at another, 

 on account of the absence of the limestone, the water is 

 duller. 



We may therefore conclude that in all probability (i) 

 The selective absorption of water determines its blue colour, 

 and that (2) The dust particles held in suspension deter- 

 mine its brilliancy. This can be familiarly illustrated. If 

 a dark metal vessel be filled with a weak solution of Prussian 

 blue, the liquid will appear quite dead and void of colour. 

 But if a little fine white powder be thrown into the solu- 

 tion, the liquid becomes of a deep blue colour; and when 

 more powder is added, the liquid becomes of a brilliant 

 blue, the brilliancy increasing with the addition of the 

 white powder. 



PASTEUR'S TREATMENT OF 

 HYDROPHOBIA. 



Extracts from the Report of the Committee of Inquiry 

 appointed by the local government board. 



IN order to answer the several questions involved in the 

 inquiry, we found it necessary that some of the mem- 

 bers of the Committee should, together with Mr. Victor 

 Horsley, the Secretary, visit Paris, so as to obtain informa- 

 tion from M. Pasteur himself, and observe his method of 

 treatment, and investigate a considerable number of the 

 cases of persons inoculated by him ; and, further, that a 

 careful series of experiments should be made by Mr. 

 Horsley on the effects of such inoculation on the lower 

 animals. The detailed facts of these observations and ex- 

 periments are placed in the Appendix to this Report ; a 

 summary of them, and the conclusions which we believe 

 may be drawn from them, are given in the next following 



The experiments by Mr. Horslej' entirely confirm M. 

 Pasteur's discovery of a method by which animals may be 

 protected from the infection of rabies. The general facts 

 proved by them may be thus stated : 



If a dog, or rabbit, or other animal be bitten by a rabid 

 dog and die of rabies, a substance can be obtained from its 

 spinal cord which, being inoculated into a healthy dog or 

 other animal, will produce rabies similar to that which 

 would have followed directly from the bite of a rabid 

 animal, or differing only in that the period of incubation 

 between the inoculation and the appearance of the charac- 

 teristic symptoms of rabies may be altered. 



The rabies thus transmitted by inoculation may, by 

 similar inoculations, be transmitted through a succession of 

 rabbits with marked increase of intensity. 



But the virus in the spinal cords of rabbits that have thus 

 died of inoculated rabies may be gradually so weakened or 

 attenuated, by drying the cords, in the manner devised by 

 M. Pasteur and related in the Appendix, that, after a cer- 

 tain number of days' drying, it may be injected into healthy 

 rabbits or other animals without any danger of producing 

 rabies. 



And by using, on each successive day, the virus from a 

 spinal cord dried during a period shorter than that used on 

 the previous day, an animal may be made almost certainly 

 secure against rabies, whether from the bite of a rabid dog 

 or other animal, or from any method of subcutaneous inocu- 

 lation. 



The protection from rabies thus secured is proved by the 

 fact that, if some animals thus protected and others not thus 

 protected be bitten by the same rabid dog, none of the first 

 set will die of rabies, and, with rare exceptions, all of the 

 second set will so die. 



It may, hence, be deemed certain that M. Pasteur has 

 discovered a method of protection from rabies comparable 



with that which vaccination affords against infection from 

 small-pox. It would be difficult to over-estimate the 

 importance of the discovery, whether for its practical utility 

 or for its application in general pathology. It shows a new 

 method of inoculation, or, as M. Pasteur sometimes calls it, 

 of vaccination, the like of which it may become possible to 

 employ for protection of both men and domestic animals 

 against others of the most intense kinds of virus. 



The duration of the immunity from rabies which is con- 

 ferred by inoculation is not yet determined ; but during 

 the two years that have passed since it was first proved 

 there have been no indications of its being limited. 



The evidence that an animal may thus, by progressive 

 inoculations, be protected from rabies suggested to M. 

 Pasteur that if any animal or any person, though unpro- 

 tected, were bitten by a rabid dog, the fatal influence of the 

 virus might be prevented by a timely series of similar 

 progressive inoculations. He has accordingly, in the insti- 

 tution established by him in Paris, thus inoculated a very 

 large number of persons believed to have been bitten by 

 rabid animals ; and we have endeavoured to ascertain with 

 what amount of success he has done so. 



The question might be answered with numerical accuracy 

 if it were possible to ascertain the relative numbers of cases 

 of hydrophobia occurring among persons of whom, after 

 being similarly bitten by really rabid anima's, some were 

 and some were not inoculated. But an accurate numerical 

 estimate of this kind is not possible. For 



(i) It is often difficult, and sometimes impossible, to 

 ascertain whether the animals by which people were bitten, 

 and which were believed to be rabid, were really so. They 

 may have escaped, or may have been killed at once, or may 

 have been observed by none but persons quite incom- 

 petent to judge of their condition. 



(2) The probability of hydrophobia occurring in persons 

 bitten by dogs that were certainly rabid depends very much 

 on the number and character of the bites; whether they are 

 on the face or hands, or other naked parts ; or, if they have 

 been inflicted on parts covered with clothes, their effects 

 may depend on the texture of the clothes, and the extent 

 to which they are torn ; and, in all cases, the amount of 

 bleeding from the wounds may affect the probability of 

 absorption of virus. 



(3) In all cases, the probability of infection from bites 

 may be affected by speedy cauterising or excision of the 

 wounded parts, or by various washings or other methods of 

 treatment. 



(4) The bites ot different species of animals, and even of 

 different dogs, are, probably, for various reasons, unequally 

 dangerous. Last year, at Deptford, five children were 

 bitten by one dog and all died ; in other cases, a dog is 

 said to have bitten twenty persons, of whom only one died. 

 And it is certain that the bites of rabid wolves, and pro- 

 bably that those of rabid cats, are far more dangerous than 

 those of rabid dogs. 



The amount of uncertainty due to these and other causes 

 may be expressed by the fact that the percentage of deaths 

 among persons who have been bitten by dogs believed to 

 have been rabid, and who have not been inoculated or 

 otherwise treated, has been, in some groups of cases, esti- 

 mated at the rate of only 5 per cent., in others at 60 per 

 cent., and in others at various intermediate rates. The 

 mortality from the bites of rabid wolves, also, has been, in 

 different instances, estimated at from 30 to 95 per cent. 



The personal investigation of M. Pasteur's cases by mem- 

 bers of the Committee was, so far as it went, entirely satis- 

 factory, and convinced them of the perfect accuracy of his 

 records. 



The number of deaths assigned by those who have sought 



