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When he started again for Paris, October 4, 1894, Pasteur 

 I was seized again with the melancholy feeling which had 

 (attended His first departure from his home, when he was sixteen 

 i years old. He saw the same grey sky, the same fine rain and 

 I misty horizon, as he looked for the last time upon the distant 

 j hills and wide plains he loved, perhaps conscious that it was 

 so. But he remained silent, as was his wont when troubled by 

 ibis thoughts, his sadness only revealing itself to those who 

 I lovingly watched every movement of his countenance. 



On October 6, the Pasteur Institute was invaded by a crowd 

 | of medical men ; M. Martin gave a special lecture in compliance 

 with the desire of many practitioners unaccustomed to labora- 

 tory work, who desired to understand the diagnosis of diphtheria 

 and the mode in which the serum should be used. Pasteur, 

 from his study window, was watching all this coming and going 

 in his Institute. A twofold feeling was visible on his worn 

 features : a sorrowing regret that his age now disarmed him for 

 work, but also the satisfaction of feeling that his work was 

 growing day by day, and that other investigators would, in a 

 similar spirit, pursue the many researches which remained to 

 be undertaken. About that time, M. Yersin, now a physician 

 in the colonies, communicated to the Annals of the Pasteur 

 Institute the discovery of the plague bacillus. He had been 

 desired to go to China in order to study the nature of the 

 scourge, its conditions of propagation, and the most efficient 

 means of preventing it from attacking the French possessions, 

 Pasteur had long recognized very great qualities in this pupil 

 whose habits of silent labour were almost those of an ascete. 

 M. Yersin started with a missionary's zeal. When he reached 

 Hong-Kong, three hundred Chinese had already succumbed, 

 and the hospitals of the colony were full ; he immediately recog- 

 nized the symptoms of the bubonic plague, which had ravaged 

 Europe on many occasions. He noticed that the epidemic 

 raged principally in the slums occupied by Chinese of the poorer 

 classes, and that in the infected quarters there were a great 

 many rats which had died of the plague. Pasteur read with 

 the greatest interest the following lines, so exactly in accord- 

 ance with his own method of observation : " The peculiar apti- 

 tude to contract plague possessed by certain animals," wrote 

 M. Yersin, " enabled me to undertake an experimental study 

 of the disease under very favourable circumstances ; it was 

 obvious that the first thing to do was to look for a microbe in 



