PREFACE. vii 



petus to the establishment of Agricultural Experimental 

 Stations in all countries, so, in like manner, have the 

 Physiology of Fermentation and Technical Bacteriology 

 called into existence, within the last few years, a number 

 of Stations and Laboratories for the development of 

 those branches of industry wherein micro-organisms play 

 an important part. Formerly, Chemistry exercised an un- 

 disputed sway over the whole of this realm, but now Biology 

 has won for itself a co-ordinate position therein a fact 

 which is now being recognised (although not yet to an 

 adequate extent) in the filling up of professorships at the 

 various Technical High Schools. An army of eager workers 

 has arisen, new technical journals have sprung into existence, 

 and a great number of treatises and books are published on 

 the subject every year. However cheering this may be in 

 itself, the fact cannot be gainsaid that a portion (unhappily 

 much too large) of these publications ought properly never 

 to have seen the light. It is true that an intimate con- 

 nection with practical conditions sets fresh tasks before 

 the investigator, and exerts on the whole a sufficiently 

 stimulating influence; but, on the other hand, the same 

 circumstance gives rise to the danger of diverging into 

 by-paths, and neglecting the strict scientific conditions of 

 investigation. Since these Stations and Laboratories are, 

 ,as a rule, maintained by the circle of practical men for 

 whom they work, the investigators appointed thereto are 

 often subjected to regrettable pressure. Even though, 

 otherwise, a certain amount of freedom is allowed them 

 in these institutions, they labour under the great difficulty 

 of being obliged whilst engaged in the task of scientific 

 investigation to be ready at any moment to give assistance 

 coupled with analyses and any wished-for disclosures 

 to the parties interested. Still further difficulties arise 

 when practical men foolishly intermeddle in scientific 

 investigations, and especially when results that shall 

 be immediately available for practical utilisation are im- 

 patiently demanded results which, however, are only 



