FERMENTATION. 10$ 



io that in fermenting tanks in which, of course, large quantities 

 5f carbonic acid gas accumulate the films are not usually met 

 ^ith. From this one may gather how laboratory experiments 

 nay go wrong, or give untranslatable results, when the exact 

 ;onditions met with in nature, or on a large scale, are not 

 idhered to ; it also explains the difiFerent results that 

 lave been obtained by various workers, the conditions in 

 :heir experiments not always being the same. For instance, 

 n Chamberland or ordinary flasks covered with filter paper 

 he film forms will develop rapidly as soon as the primary 

 ermentation is completed ; whilst in the closed Pasteur 

 lasks, in which the air cannot be changed rapidly, the 

 ilms grow comparatively slowly. 



To produce these films Hansen proceeded as follows : 

 laving obtained his pure cultivations, drop cultures were 

 nade into car.efully sterilized four-ounce flasks, half filled with 

 terilized wort and protected from falling particles by being 

 :overed with sterilized filter paper. As soon as the films be- 

 :ame apparent to the naked eye they were examined. They 

 ippear, according to Hansen, as small opaque points, which 

 Gradually increase in size and then run together, forming 

 rregular patches floating on the upper surface, with a con- 

 vexity on the side resting on the fluid. The film at length 

 )verspreads the whole surface and becomes adherent to the 

 vail of the flask at the margins ; on shaking the flasks much 

 )f the film can be made to sink, but a new one forms to fill 

 ip the gaps that are left. 



These young films he divided into two groups, the first 

 onsisting of Sacch. cerevisiae, Sacch. Pastorianus II., Sacch. 

 llipsoideus II., in none of which could he find mycelium-like 

 olonies (at one time it seemed that Hansen's researches had 

 iemonstrated this fact) ; whilst in the second group, which 

 ncluded Sacch. Pastorianus I. and III. and Sacch. ellipsoideus 

 ., such mycelial colonies were early developed. Later 

 esearches have tended to show that this division is very 

 nuch a matter of time, and that it cannot now be looked 

 ipon as having any real scientific value. 



As regards the temperature at which these films are 

 leveloped Sacch. cerevisiae and Sacch. ellipsoideus I. are 

 ieveloped between 38° and 6° C, the three Pastorianus 

 'arieties between 34° and 3° C. ; Sacch. ellipsoideus II., 38° 

 o 40° C, and 3° C. The film of this latter appears to be the 



