138 PERIOD V. 



the work of living* microscopic organisms as alcoholic 

 fermentation. In 1857 and the following- years Pasteur 

 not only confirmed the work of Schwann, which had 

 been received by the majority of chemists with distrust, 

 but went on to show that the lactic, butyric, and 

 ammoniacal fermentations also depend upon the activity 

 of bacteria. The happy thought struck him that they 

 might be studied alive — a possibility which he soon 

 realised in practice, and upon which the new science of 

 bacteriology largely rests. From about the year 1873 

 he began to occupy himself seriously with contagion, 

 which he suspected to be connected with specific aerial 

 germs. Davaine and others had years before observed 

 in the blood of sheep and cattle which had died of 

 " charbon " (anthrax) minute " bdtonnets " (bacilli). 

 Pasteur's published results induced Davaine to ask 

 whether his " b^tonnets " might not be the cause of 

 "charbon." Again, it was Pasteur's results which 

 induced Lister to make experiments in the field of 

 antiseptic surgery. Pasteur wasted no time upon the 

 curiosities of bacterial life. His first studies on fermen- 

 tation suggested that specific diseases may be propa- 

 gated by microscopic germs, and that such cases of 

 spontaneous generation as had hitherto escaped refuta- 

 tion might be explained by the access of live dust. 

 The identification and biological history of the organisms 

 interested him only as a step towards sure methods of 

 controlling, and, if necessary, destroying, them ; of 

 mitigating their virulence by inoculation ; of rendering- 

 animals immune against them ; or of stamping out the 

 disease by isolation. All this is happily too well known 

 for repetition here. The story, with its many dramatic 

 incidents, can be read in the pages of Vallery-Radot. 

 Hardly less important than the bacteria which destroy 



