CYTOLOGY OF YEASTS 271 



granules in question. ^ If fresh preparations of young yeast cells are 

 stained by Gram's method, all the cells stain a uniform deep blue- 

 black. VThe Alberts showed that, if yeast cells were killed by a pro- 

 cedure which did not destroy their enzymes (treatment with acetone) 

 and were then suspended in water, they would undergo autolysis. If 

 now one makes preparations of these autolyzing cells and stains by 

 Gram's method, it will be found that, as autolysis proceeds, part of 

 the protoplasm fails to retain Gram's stain, and large numbers of 

 Gram-positive granules appear in the Gram-negative matrix. As 

 autolysis proceeds, these granules become fewer in number and 

 finally disappear. The disappearance of the granules is accompanied 

 by increasing amounts of protein in the water, i.e., there is a corre- 

 lation between the Gram-staining of the granules and their resistance 

 to autolysis. 



If now one prepares a series of slides of fresh, non-autolyzed 

 yeasts, stains by Gram's method, and decolorizes wdth different 

 strengths of acid alcohol instead of the plain alcohol ordinarily used, 

 an exactly similar series of preparations is obtained. That is, a 

 slide of fresh yeast decolorized with say 1 per cent acid alcohol will 

 appear like a slide of yeast W'hich has autolyzed say 1 hour; if de- 

 colorized with 5 per cent acid alcohol it will appear like a slide of 

 yeast which has autolyzed 2 hours; and so on. Thus one may dem- 

 onstrate in the protoplasm of the freshly fixed yeast cell a whole 

 series of fine protein granules which vary in their tenacity of Gram's 

 stain, and this variation is correlated with their resistance to au- 

 tolysis after the cell has died. These studies also indicate that the 

 Gram-staining property is not resident in the membrane, as has been 

 claimed, but in proteins contained in the protoplasm, at least as far 

 as yeasts are concerned. 



Another very prominent feature of the yeast cell is the presence of 

 material known as volutin or metachromatic material. It occurs in 

 all the higher fungi and in bacteria as well, but is especially promi- 

 nent in the yeasts. Practically every cell contains at least one 

 vacuole filled with this material situated near the nucleus (Fig. 112). 

 These granules are less refractile than the fat vacuoles. Generally 

 the vacuoles contain a small granule which exhibits an active Brown- 

 ian movement, frequently referred to as the dancing body. This 

 Brownian movement indicates that the vacuole contains fluid of not 

 very high viscosity. The granule within the vacuole may some- 

 times suddenly disappear, and after a time as suddenly reappear. 

 This fact, together with the fact that both the fluid of the vacuole 



