lyo CHEMISTRY OF THE YEAST CELL. 



will remaiu, whilst the red-brown will vanish — to reappear in 

 its original intensity on cooling. If the cells of the treated 

 preparation be i-uptured by applying pressure to the cover 

 glass, a rapid examination under the microscope will show that 

 the browned constituents quickly dissolve in the surrounding 

 fluid on escaping from the cells, the residual portion exhibiting 

 the customary yellow coloration furnished by albuminoids on 

 treatment with iodine. If present in any considerable amount, 

 the glycogen becomes visible to the microscopist by virtue of its 

 optical properties, even in unstained preparations. In such 

 event it is seen in the cells as a semi-fluid, whitish opalescent 

 mass of strong refractive power. Sometimes it takes up a 

 position in such portions of the cell contents as are nearest the 

 walls; but in others, as recoi-ded by Errera (V.), it collects 

 in one place and assumes the shape of a semilunar aggregation. 



The separation and recovery of fungoid glycogen by macro- 

 chemical means was first successfidly accomplished by Errera 

 (II.), though the quantities obtained were insuflicient for the 

 lequirements of an accuiute macrochemical examination. This 

 difficulty was first overcome by M. Cremer (III.) in 1894, who 

 was then able to show that the glycogen of yeast is identical 

 with that in the liver of animals, and that too, not merely in 

 respect of the propeities aforesaid, but also with reference to its 

 I'esistance to the action of Fehling's solution and its behaviour 

 on hydrolysis by dilute hydrochloric acid (as also by diastase, 

 saliva, and the panci'eatic enzyme), dextrose being produced. 

 E. Salkowski's report (lY.) that yeast glycogen and liver glycogen 

 differ, inasmuch as the former is partly conveited into cellulose 

 on being heated to i 7.0" C. alonsr with a little water, was not 

 confirmed l)y Cre.meii (III). At all events, the optical rotatory 

 power of yeast glycogen was found to be lower («,,= + 198.9°) 

 than that of animal elvcogen, for which the values in the literature 

 differ and are in pai't considerably higher (up to 235"). 



For comprehensive researches into the chemistry of this 

 carbohydi-ate we are indebted to a pupil of Errera's, namely 

 G. Clautriau (I.), to whose work the interested reader is referred, 

 especially as regaids the choice of the best method of isolating 

 glycogen from the different species of fungi. Glycogen is 

 amorphous, and therefore cannot be prepared in the pure state 

 by the crystallisation process, but cont;iins an admixture — larger 

 or .smaller in accordance with the oriijin and care bestowed on 

 the manufacture — of other organic and inorganic cell con- 

 stituents. This })ossibility should be kept in mind when mention 

 is made of small discrepancies, similar to those found in animal 

 glycogen by earlier workers, and also by Clautriau in comparing 

 yeast glycogen with that obtained from other fungi. Thus the 

 angle of rotation found by this worker, in the case of yeast 

 glycogen, was 184.5°, whereas in that from Amanita muscaria 



