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318 PASTEUR: THE HISTORY OF A MIND 



immediate attention to them. It is his letter, inserted 

 in the first number of the Annales de VInstitut Pasteur, 

 which first pointed out to the French public the re- 

 searches of M. Metchnikoff. 



The simplicity of this conception was striking. These 

 white corpuscles of the blood and of the tissues, playing 

 the role of gendarmes in the organism, constantly in 

 circulation, always ready to throw themselves on every- 

 thing foreign appearing there, and consequently upon 

 enemies living or dead, surrounding by virtue of this 

 general property the cells of the microbes, digesting 

 them and making them disappear all that could not 

 fail to captivate him! The idea was the idea of a biolo- 

 gist and of a naturalist; it had not occurred to Pasteur, 

 but that did not prevent him from welcoming it with 

 deference. As long as he lived, he wished to keep in 

 touch with its progress. 



It pleased him so much the more that after remaining 

 for sometime in the field of anatomy and natural history, 

 the problem was not long in returning to the field of 

 chemistry, to which all our conceptions, whatever may 

 be their objects, provided they are deep, are not slow 

 in returning, because, at bottom, it is chemical mutations 

 which govern everything. 



The theory of Metchnikoff had, moreover, for his 

 mind, this satisfying side that it equalized the competi- 

 tive forces. There is something disproportionate in a 

 bacteridium which kills an ox. One understands better 

 a localized struggle between the leucocytes of the ox 

 and the invading microbes, which perish if they are 

 too feeble, or too few in number, but which take posses- 

 sion of everything if they are the stronger, because they 

 have the power of multiplication in their favor. 



Nevertheless, thus limited and defined, the conditions 

 of the struggle remained hazy and somewhat mysterious. 



