80 THE LIFE OF PASTEUR 



by the method of cultures of organisms in a Btate of purity ; a 

 method by which I have solved, within the last twenty-two 

 bi< f difficulties relative to fermentations properly 

 so called; notably the important question, much debated for- 

 merly, of the correlation which exists between those fermenta- 

 tions and their particular ferments." 



He then pointed out that if. after gathering either blood or 

 pus immediately before or immediately after the death of a 

 plague patient, one could succeed in discovering the micro- 

 organism, and then in finding for that microbe an appropriate 

 culture medium, it would be advisable to inoculate with it ani- 

 mals of various kinds, perhaps monkeys for preference, and to 

 look for the lesions capable of establishing relations from cause 

 to < fleet between that organism and the disease in mankind. 



He did not hide from himself the great difficulties to be met 

 with in experimenting; for, after discovering and isolating the 

 riism, there is nothing to indicate a priori to the experi- 

 mentalist an appropriate culture medium. Liquids which suit 

 some microbes admirably are absolutely unsuitable to oth- 

 Cake, for instance, the microbe of chicken-cholera, which will 

 not develop in beer yeast ; a hasty experimentalist might con- 

 clude that the chicken -cholera is not produced by a micro- 

 organism, and that it is a spontaneous disease with unknown 

 immediate causes. 'The fallacy would be a fatal one." said 



iteur, "for in another medium, say, for instance, in 

 cken-broth, there would be a virulent culture." 



Tn these researches on the plagui . then, various mediums 

 should be tried ; also the char <■!, r. either aerobic or anal 

 of the microbe should be present to the mind. 



' The sterility of a culture liquid may come from the presence 

 of air and not from its own constitution ; the s- ptie vibrio, for 

 instance, is killed by oxygen in air. From this last circum- 

 stance it is plain that culture must be made not only in the 

 presence of air but also in a vacuum or in the presei 

 of pure oic acid gas. In the latter cast . imme- 



diately after sowing the blood or humour to be tested, a 

 ■uum must b le in the tubes, they must be sealed bv 



means of a lamp, and left in a suitable temperature, usually 



: ' Thus he | : • imarks for 



the guidance of scientific research on the i nology of the plague. 



siring as Pasteur did thai the public in general should take 



