STUDIES OlS FERMENTATION. • 147 



of yeast cells which we have seen undergo this process of 

 rupture in the course of some ten years of ohservation, every 

 day of which, we may say, thousands of these cells have passed 

 under our eyes. This breaking up of the cells is really of the 

 most rare occurrence, and may always be explained by some 

 abnormal circumstance affecting the yeast ; being indeed a 

 mechanical accident, not a physiological fact. We may easily 

 convince ourselves of this by growing some yeast in a saccharine 

 wort, filtered perfectly clear, and, consequently, deprived of all 

 granular amorphous deposit that might deceive the observer. 

 The cells will be observed to bud and multiply without exhibit- 

 ing the most minute appearance of granulation, or disruption ; 

 moreover, there will always be cells of all sizes, ranging from 

 the smallest visible up to the largest. This very simple piece of 

 observation may be made in all the alcoholic ferments, and with 

 any wort capable of fermenting, and in its presence the 

 hypothesis, which we have been repudiating, cannot hold its 

 own. 



In Plate VII. (left side) there is represented a field of yeast, 

 magnified 400 times. We see a mass of disjointed cells, such as 

 appear after fermentations without sufficient aliment ; of the 

 kind represented some are nearly spherical, others oval or 

 cylindrical, more or less elongated. If we mix a little of this 

 yeast, of about the size of a pin's head, with wort, and put the 

 wort into a small, shallow, flat-bottomed basin, having a surface 

 of about 1 square decimetre (10 sq. ins.) exposing it to the 

 surrounding temperature, we shall find next day the bottom of 

 the basin covered with a fine white deposit, of the forms of 

 which we give a sketch in the right half of the plate. In this 

 it will at once be observed that the cells sown have lost their 

 interior granulations, having become more transparent and 

 filled with a gelatinous protoplasm. The principal difi'erence 

 between the two halves of the plate consists in this, that 

 whereas the cells in the left half are isolated and granular, those 

 in the right half are more inflated, more transparent, and pro- 

 vided with budS; which may be seen in every stage of development, 



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