154 



ANATOMY OF THE YEAST CELL. 



appear in large numbers at the close of primary fermentation, 

 and are usually very abundant in permanent cells (§ 245). 

 Naturally, the method of nutrition has also some influence on 

 their occvirrence. Thus, G. Hieronymus (I.) found only very 

 few granules in the cells of pressed yeast that had been grown 

 in a nutrient- salt solution containing grape sugar, whereas 

 they weie abundant in such cells as had been kept in milk or a 

 solution of beet sugar. According to a report by Joh. Raum 

 (II.), no granules are formed when sugar is absent from the 

 nutrient substratum. 



It is to the last-named worker that we are indebted for the 

 first accurate investigations in connection with these inclusions. 

 These researches are the more valuable in that they were ex- 

 clusively performed on pure cultures, namely, of ten species of 

 budding fungi, comprising six true ISacrharomycetes (8. cerevisice 



Fig. 152. — Permanent Cells 

 of bottom-fermentation beer yeast, either partially or entirely filled with granules, 

 wall considerably thiclcened. Magn. 2000. (Ajter M'iU.) 



Cell 



/. Hansen, S. ellipsoideus I. and 11. H., S. Pastorianus 1. H . 

 pressed yeast from Warsaw, and a yeast from the air), a 

 red budding fungus termed S. ghitimis, a so-called black yeast, 

 and a budding fungus from Kephir granules. The occurrence 

 of the inclusions in cjuestion was demonstrated in all these 

 species. The number fluctuates considerably, and very often 

 far exceeds a dozen. Their dimensions were also found to vary 

 considerably. When a large number nre present, they are com- 

 paratively minute (Fig. 152), generally only a few tenths of a 

 micromillimetre in diameter ; but when the number is smaller 

 (and it may sink to unity), the size attains considerable pro- 

 portions. In the latter event they may readily be mistaken, by 

 the inexperienced eye, for ascospores, owing to the high refrac- 

 tive power they have in common with the latter. In doubtful 

 cases the uncertainty may be removed by the aid of some of the 

 microchemical reactions given below. Moreover, these granules 

 are not always of the same shape ; for the most part they are 

 globular, though specimens with an angular contour are by no 

 means infrequent. In throwing doubt on the existence of this 

 latter modification, and opining that it only appears on staiiiing, 



