458 THE LIFE OF PASTEUR 



the blood of the patients and in the bubonic pulp." When 

 M. Yersin inoculated rats, mice, or guinea-pigs with this pulp, 

 the animals died, and he found several bacilli in the ganglions, 

 spleen, and blood. After some attempts at cultures and inocula- 

 tions, he concluded thus : " The plague is a contagious and 

 inoculable disease. It seems likely that rats constitute its 

 principal vehicle, but I have also ascertained that flies can 

 contract the disease and die of it, and may therefore become 

 agents for its transmission." 



At the very time when M. Yersin was discovering the specific 

 bacillus of the plague in the bubonic pulp, Kitasato was making 

 similar investigations. The foe now being recognized, hopes 

 of vanquishing it might be entertained. 



And whilst those good tidings were arriving, Pasteur was 

 reading a new work by M. Metchnikoff, a Eussian scientist, 

 who had elected to come to France for the privilege of working 

 by the side of Pasteur. M. Metchnikoff explained by the 

 action of the white corpuscles of the blood, named " leuco- 

 cytes," the immunity or resistance, either natural or acquired, 

 of the organism against a defined disease. These corpuscles 

 may be considered as soldiers entrusted with the defence of the 

 organism against foreign invasions. If microbes penetrate into 

 the tissues, the defenders gather all their forces together and a 

 free fight ensues. The organism resists or succumbs accord- 

 ing to the power or inferiority of the white blood-cells. If the 

 invading microbe is surrounded, eaten up, and ingested by the 

 victorious white corpuscles (also named phagocytes), the latter 

 find in their victory itself fresh reserve forces against a renewed 

 invasion. 



On November 1, in the midst of all this laborious activity 

 and daily progress, Pasteur was about to pay his daily visit 

 to his grandchildren, when he was seized by a violent attack of 

 ursemia. He was laid on his bed, and remained nearly uncon- 

 scious for four hours ; the sweat of agony bathed his forehead 

 and his whole body, and his eyes remained closed. The even- 

 ing brought with it a ray of hope ; he was able to speak, and 

 asked not to be left alone. Immediate danger seemed avoided, 

 but great anxiety continued to be felt. 



It was easy to organize a series of devoted nurses ; all 

 Pasteur's disciples were eager to watch by his bedside. Every 

 evening, two persons took their seats in his room : one a 



