NA TURE 



433 



THURSDAY, SEPTEMBER 



HYDROPHOBIA. 



THE culmination of scientific knowledge in any special 

 direction frequently appears to the casual observer 

 as a sudden and unforeseen event, although actually the 

 result of a combination of well-ascertained facts accumu- 

 lated during many years. The introduction of rabies from 

 among the inexact to among the more exactly known 

 diseases has been however so rapid as to very fairly 

 substantiate this popular belief. It is now scarcely more 

 than three years ago since the self-sacrificing labours of 

 M. Pasteur helped us to pass from superstition to accurate 

 knowledge of the real nature of rabies or hydrophobia, 

 and this passage from the pre-scientific to the scientific 

 epoch of the subject was actually perfectly abrupt. Nearly 

 the same thing may also be said of the discovery by 

 Koch of the Bacillus tuberculosis, for in both cases the 

 scientific grasp of the subject undoubtedly commenced 

 with the discovery how the virus might be isolated for 

 purposes of experiment. While, however, this is strictly 

 the case with tuberculosis, it is but partially true for rabies, 

 for though there cannot be a shadow of doubt that the 

 micro-organism which is the virus of rabies will soon be 

 demonstrated in pure cultivations, this one factor is yet 

 wanting to place it on the same level as that of tubercu- 

 losis. This difficulty in obtaining pure cultures, though a 

 serious defect in our information, is yet most interesting, 

 for it affords a distinct interpretation of several facts in 

 the etiology of the disease, which, as we shall see directly, 

 proved obstacles to early inquirers, and which yet at the 

 same time, when viewed in the present light of science, 

 are most encouraging to those who are anxious to see this 

 miserable evil extinguished for ever. 



All observers, notably Mr. Dowdeswell, are agreed that 

 a micrococcus can be demonstrated in the tissues of the 

 spinal cord of animals affected with the disease, but 

 unless we accept the doubtful results of Fol no one has 

 yet succeeded in cultivating this micrococcus. Those 

 familiar with the difficulties of "rearing" pathogenic 

 organisms will readily understand this obstacle in a 

 disease with such a long incubation period as rabies. 



M. Pasteur at the outset of his investigations attempted 

 to solve the problem in this direction, but fortunately for 

 science soon abandoned it in view of the probability that 

 the virus would best be dealt with by endeavouring to 

 obtain it in quantity from the central nervous system, since 

 from the symptoms it evidently there produced its greatest 

 effect, and so might be expected to be more especially 

 present. He therefore made an emulsion by crushing 

 in sterilized bouillon portions of the central nervous 

 system, specially the spinal cord. With this emulsion he 

 inoculated the disease from animal to animal by injecting 

 a small quantity of it beneath the dura mater. By this 

 simple procedure he established the first of his most 

 important discoveries, viz. the real incubation period of 

 the disease. At the same time too, as is usual in instances 

 of a genuine scientific advance, the one important dis- 

 covery led to a further one, since he has thus presented 

 science with an infallible means of determining whether 

 an animal had really suffered from the disease or not. 

 Vol. XXXVI. — No. 932. 



To the public this test has already been of the utmosi 

 value, since, as is well known, the characteristic lesions in 

 the alimentary canal, &c., being absent or but feebly 

 marked in the early stages of the disease, the possibility 

 of thus giving a definite opinion in cases of doubt by the 

 aid of Pasteur's method has frequently been the means ol 

 affording the utmost relief to the minds of those who have 

 been victims to the lingering dread of hydrophobia. We 

 are not aware however that the slightest public expressior 

 of gratitude has ever been expressed in this country 

 towards that experimental science which in M. Pasteur's 

 hands has led to such an important result, or that we, whc 

 by reason of rabies being endemic among us are profiting 

 and will profit, enormously by the light thus shed on the 

 subject, have acknowledged our indebtedness to him ir 

 any way. 



From his researches M. Pasteur was led on to formulate 

 certain deductions which might be accepted as the logica 

 consequence of the theory of the disease thus shown by 

 him to be indubitably zymotic. 



In the first place, M. Pasteur considered it probable 

 that he could attenuate the virus which he had just diS' 

 covered the possibihty of handling with certainty, and we 

 may add safety. This he soon accomplished by the 

 method of drying. 



It might naturally be supposed that, having proceedec 

 thus far, he would have been led to attempt protectior 

 from, and prevention of, the evil effects of the disease by 

 inoculating with this attenuated virus. Indeed it is 

 unfortunately the popular belief that he did do this, and 

 that his efforts to cure the malady are conducted upor 

 this plan. 



As a matter of fact, however, M. Pasteur, with a much 

 wider prescience of the facts and theories of zymotic 

 disease in general, considered that the well-known arrest 

 of development which happens to virulent organisms as 

 a consequence of their growth in tissues or in artificial 

 culture media was due to the production by theii 

 metabolic processes of katalyzed substances whose 

 presence was inimical to the active growth of the 

 microbe, and that therefore these substances might be 

 regarded and used as antidotes to the virus. Acting or 

 this assumption, he proceeded to endeavour to protect 

 animals by injecting into them considerable quantities 

 not of the virus, as generally supposed, but of these 

 antidotal substances, or possibly of one alone. Ol 

 course, knowing that as a rule attempts to isolate in £ 

 state of chemical purity such products usually failed 01 

 seriously altered them, and having already ascertained 

 that the baleful influence of the virus could be abrogated 

 or rendered nugatory by the process of drying, he pro- 

 ceeded to employ the simple method of injection emul- 

 sions of dried spinal cords. The injection of such 

 emulsions was naturally performed understanding that 

 the drying would probably also impair to a certain ex- 

 tent the protective value of the antidotal substance ; to 

 insure, therefore, the introduction into the animal of as 

 large a quantity as possible he considered it advisable to 

 inject emulsions on successive days from spinal cords 

 which had been dried for shorter and shorter periods, till 

 ultimately, having commenced by inoculating from cords 

 which had been dried for fourteen days, and which had 

 been proved to be perfectly innocuous, he arrived at a 



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