Sepxembee 25, 1896.] 



SCIENCE. 



423 



But to return to Pasteur. In 1880 lie 

 entered upon the study of that terrible but 

 then most obscure disease, hydrophobia, or 

 rabies, which from its infective character 

 he was sure must be of microbic origin, 

 although no micro-organism could be de- 

 tected in it. He early demonstrated the 

 new pathological fact that the virus had its 

 essential seat in the nervous system. This 

 proved the key to his success in this sub- 

 ject. One result that flowed from it has 

 been the cause of unspeakable consolation 

 to many. The foolish practice is still too 

 prevalent of killing the dog that has bitten 

 any one, on the absurd notion that, if it 

 were mad, its destruction would prevent the 

 occurrence of hydrophobia in the person 

 bitten. The idea of the bare possibility 

 of the animal having been so affected 

 causes an agony of suspense during the 

 long weeks or months of possible incuba- 

 tion of the disease. Very serious nervous 

 symptoms aping true hydrophobia have been 

 known to result from the terror thus in- 

 spired. Pasteur showed that if a little 

 of the brain or spinal cord of a dog that 

 had been really mad was inoculated in an 

 appropriate manner into a rabbit, it infal- 

 libly caused rabies in that animal in a 

 few days. If, therefore, such an experi- 

 ment was made with a negative result, the 

 conclusion might be drawn with certainty 

 that the dog had been healthy. It is per- 

 haps right that I should say that the inocu- 

 lation is painlessly done under an anaesthe- 

 tic, and that in the rabbit rabies does not 

 assume the violent form that it does in the 

 dog, but produces gradual loss of power, 

 with little, if any, suffering. 



This is the more satisfactory because rab- 

 bits in which the disease has been thus 

 artificially induced are employed in carrj^- 

 ing out what was Pasteur's greatest tri- 

 umph, the preventive treatment of hydro- 

 phobia in the human subject. We have 

 seen that Pasteur discovered that microbes 



might under some circumstances undergo 

 mitigation of their virulence. He after- 

 wards found that under different conditions 

 they might have it exalted, or, as he ex- 

 pressed it, there might be a renforcement du 

 virus. Such proved to be the case with 

 rabies in the rabbit ; so that the spinal cords 

 of animals which had died of it contained 

 the poison in a highly intensified condition. 

 But he also found that if such a highly 

 virulent cord was suspended under strict 

 antiseptic precautions in a dry atmosphere 

 at a certain temperature, it gradually from 

 day to day lost it potency, till in course of 

 time it became absolutely inert. If now 

 an emulsion of such a harmless cord was 

 introduced under the skin of an animal, 

 as in the subcutaneous administration of 

 morphia, it might be followed without harm 

 another day by a similar dose of a cord still 

 rather poisonous ; and so from day to day 

 stronger and stronger ejections might be 

 used, the system becoming gradually accus- 

 tomed to the poison, till a degree of viru- 

 lence had been reached far exceeding that 

 of the bite of a mad dog. When this had 

 been attained, the animal proved incapa- 

 ble of taking the disease in the ordinary 

 way ; and more than that, if such treat- 

 ment was adopted after an animal had 

 already received the poison, provided that 

 too long a time had not elapsed, the out- 

 break of the disease was prevented. It 

 was only after great searching of heart 

 that Pasteur, after consultation with some 

 trusted medical friends, ventured upon try- 

 ing this practice upon man. It has since 

 been extensively adopted in various parts 

 of the world with increasing success as the 

 details of the method were improved. It 

 is not, of course, the case that every one 

 bitten by a really rabid animal takes the 

 disease ; but the percentage of those who 

 do so, which was formerly large, has been 

 reduced almost to zero by this treatment, 

 if not too long delayed. 



