18 LOUIS PASTEUR. 



his career he has enjoyed an uninterrupted success. The French 

 people have slowly learned to recognise this, and finally acquired 

 such a confidence in him that it has been a popular saying which 

 has met all criticisms that " Pasteur never makes mistakes^ This 

 unique testimony of public confidence is unexampled, but it 

 seems to have been well deserved, for certainly no scientist has 

 ever held such a position before the public and made so few mis- 

 takes. This is the more remarkable when we remember that he 

 was working in an almost unexplored field. The reason for this 

 uniform success lies primarily doubtless in the nature of the man ; 

 but not a little of it we may attribute to the fact that in his early 

 training Pasteur was a chemist rather than a biologist. While 

 Pasteur's reputation will rest upon his work in biology he was edu- 

 cated as a chemist, and to this education we may attribute no 

 little of the uniformity of the success of experiments. The 

 science of biology is extremely inexact. Owing to the complicated 

 conditions of life one is ever expecting to find exceptions to the 

 general rules, and our scientists have found it utterly impossible to 

 lay down absolute definitions or any absolute lines of distinction 

 between groups in biological phenomena. The very essence of 

 biological science is the fact that the phenomena grade into each 

 other. Influenced by this fundamental principle, biologists have 

 commonly fallen into a habit of slackness in dealing with pheno- 

 mena. Knowing that whatsoever law they may discover will be 

 sure to have its modifications, its variations, and its exceptions, 

 they inevitably get into the habit of feeling that an approximation 

 toward accuracy is almost sufficient. Now, the peculiar nature of 

 the field of experimentation in bacteriology demands above all 

 things most rigid accuracy. His training as an analytical chemist 

 gave to Pasteur a recognition of the importance of exactness. 

 One who has carried on experiments in molecular physics recog- 

 nises that failure is sure to result from inaccuracy ; and it was the 

 fact that until he was 30 years of age Pasteur was trained in this 

 kind of accurate experimental manipulation that, when he turned 

 his attention finally to biology and problems connected with the 

 microscopical world, his methods of experimentation and the 

 results of the experiment showed at once a vast advance over 

 those of all of the biologists which had preceded him. For the 

 first time accuracy began to be seen in this field. 



