172 STUDIES ON FERMENTATION. 



of carbohydrate food which we introduce along with the 

 specimen. An interior chemical action also goes on, causing a 

 gradual change in the aspect of the yeast. The plasma of the 

 cells collects about the centres, assuming a yellowish-brown 

 colour, becoming granular, and forming within the cells masses 

 more or less irregular in shape, very rarely spherical. 



We may observe here that these conditions seem to be 

 peculiarly adapted to show the character of the interior sporula- 

 tion of the cells discovered by Dr. Rees. Notwithstanding this 

 we have never succeeded in finding it distinctly, under these 

 circumstances. 



The fact which should claim all our attention, we repeat, is, 

 that this exhausted, shrivelled-up, aged-looking yeast preserves 

 its faculty of germination for several years ; that, moreover, 

 this faculty may be aroused by placing it in aerated nutritive 

 media, in which case it will exhibit all the peculiarities which, 

 under similar conditions, characterize some of the germ-cells 

 found on the surface of our sweet domestic fruits. In other 

 words, this yeast, instead of multiplying, as it always does 

 in the course of several growths in saccharine musts, in the 

 form of cells which detach themselves readily as soon as they 

 have nearly attained the form and size of the mother-cells, begins 

 to shoot out into such beautiful forms as those of dematiain 

 pullulans, producing like that ferment long, well-grown, branch- 

 ing filaments, as well as plump and frequently pyriform cells, 

 as represented in Plate X. 



The following figures (33 to 37) and descriptions of the ob- 

 servations to which they relate will furnish fresh proofs of our 

 assertions. In these figures we see saccharomyces jmstorianus, 

 which has been exhausted in sweetened water or in yeast-water, 

 undergo revival in saccharine musts, give rise to elongated, 

 branching, pear-shaped forms, such as belong to the original 

 ferments of fruits, and afterwards assume the most minute 

 forms that we find in fermentations progressing or completed. 



Let us examine Fig. 33. The history of this growth is as 

 follows : — 



