FOREWORD xv 



point the old researches of Devaine ; but he did much more, 

 and for the first time isolated the organism in pure culture 

 outside the body, grew successive generations, showed the 

 remarkable spore formation, and produced the disease arti- 

 ficial^ in animals by inoculating with the cultures. Pasteur 

 confirmed these results, and in the face of extraordinary opposi- 

 tion succeeded in convincing his opponents. Out of this study 

 came a still more important discovery, namely, that it was 

 possible so to attenuate or weaken the virus or poison that the 

 animal could be inoculated, and have a slight attack, recover, 

 and be protected against the disease. More than eighty years 

 had passed since, on May 14th, 1796, Jenner, with a small 

 bit of virus taken from a cow-pox on the hand of the milkmaid, 

 Sarah Newlme, had vaccinated a child, and thus proved that a 

 slight attack of one disease would protect the body from disease 

 of a similar character. It was an occasion famous in the 

 history of medicine, when, in the spring of 1881, at Melun, at 

 the farmyard of Pouilly le Fort, the final test case was deter- 

 mined, and the flock of vaccinated sheep remained well, while 

 every one of the un vaccinated, inoculated from the same 

 material, had died. It was indeed a great triumph. 



The studies on chicken cholera, yellow fever, and on swine 

 plague helped to further the general acceptance of the germ 

 theory. I well remember at the great meeting of the Inter- 

 national Congress in 1881, the splendid reception accorded to 

 the distinguished Frenchman, who divided with Virchow the 

 honours of the meeting. Finally came the work upon one of 

 the most dreaded of all diseases — hydrophobia, an infection of 

 a most remarkable character, the germ of which remains un- 

 discovered. The practical results of Pasteur's researches have 

 given us a prophylactic treatment of great efficacy. Before its 

 introduction the only means of preventing the development of 

 the disease was a thorough cauterisation of the disease wound 

 within half an hour after its infliction. Pasteur showed that 

 animals could be made immune to the poison, and devised a 

 method by which the infection conveyed by the bite could be 

 neutralised. Pasteur Institutes for the treatment of hydro- 







