8 BACTERIA. 



than deductions made as the results of sober scientific 

 investigation and thought. These men have also, how- 

 ever, been able to obtain many new facts, and to point 

 out the gaps that still remain to be filled in before the 

 theories so admirably expounded can be proved to demon- 

 stration. The French can boast of their Davaine and Pasteur, 

 who, assisted by Chauveau and others, have given to us the 

 germ theory of disease and the theories of fermentation and 

 protective inoculation. In Germany, Klebs, Cohn, Koch, 

 and their followers, have made marvellous contributions to 

 the study of bacteria, and additions to our knowledge of their 

 relation to disease. The Danes have furnished O. F. Miiller, 

 Warming, Panum, Salomonsen, Bang, and Chr. Hansen, 

 who, seizing most of what was good in both the French and 

 German schools, have succeeded in making most valuable 

 contributions to various branches of the subject ; whilst, in 

 this country, Burdon Sanderson, Greenfield, Klein, Watson 

 Cheyne, and others, have all contributed their share, though 

 Lister's name must always stand pre-eminent for the mag- 

 nificent work which he has done in the domain of antiseptic 

 surgery, by the evolution and perfecting of which he has 

 done more, both directly and indirectly, to ameliorate the 

 suffering, and to diminish the mortality in surgical cases, 

 than has been achieved by the most brilliant operators the 

 world has produced during the last century. 



Many of the processes of everyday life are intimately 

 associated with the specific activities of micro-organisms ; we 

 are constantly meeting with these organisms, and it is now 

 proved, beyond all dispute, that their presence is not merely 

 accidental but is absolutely essential to the carrying on of, 

 one might almost say, the most commonplace operations. 

 Take, for example, those that are associated with the different 

 processes of fermentation. Leaving for the moment the 

 yeasts or saccharine ferments, I may refer first to the 

 butyric acid ferment — Clostridium butyricum — which plays 

 a most important part in interfering with the ordinary course 

 of the saccharine fermentation. It decomposes starch and 

 cellulose without requiring the presence of oxygen ; it, like 

 other micro-organisms, appears to require for its nutrition, 

 nitrogenous material, and, especially in the presence of the 

 lactic acid ferment, it brings about the conversion of sugar 

 into butyric acid ; it is, as might be anticipated, one of the 



