1917] Mitra: Toxic and Antagonistic Effects of Salts on Wine Yeast 79 



The measurements given are the average of five counts in each 

 case. The volumes from which the curves have been drawn in figure 5 

 (a, b) have been calculated, for purposes of comparison, as though 

 the cells were cylindrical. 



Both from table 5 (a, b, c, el) and the curves in figure 5 (a, b) it 

 is evident that KC1 and MgCL favor growth in size up to the most 

 favorable concentration, beyond which the cells decrease in size until 

 the extreme concentration is reached, where they dissolve. Both NaCl 

 and CaCL limit the growth even in minute concentrations, thus show- 

 ing their extreme toxicity to yeast cells. 



Yeast cells seem to have remarkable resistant power. Many of 

 them with cell wall thickened to a heavy membrane have been found 

 in extreme concentrations. Perhaps this heavy membrane is formed 

 to resist the osmotic pressure outside the cell. I'm 'sides some of the 

 cells in these extreme concentrations are in normal condition and are 

 even budding, thus showing the power of adaptability of yeast cells 

 to new conditions. After they have become habituated to the presence 

 of toxic salts, they grow normally and reproduce. It is probably 

 owing to flie adaptability of yeast to different conditions that the 

 same yeast, S. ellipsoideus, collected from various sources, shows dis- 

 similar physiological characters. Besides in many cases I have 

 observed that the diseased yeast cells in extreme toxicity of KC1 and 

 MgCL, form a white membrane with normal cell contents, while those 

 of CaCL and NaCl form a rather dark cell membrane with shadowy 

 cell contents. A similar case to that of Loeb 5, 13 may be cited here. 

 In his experiments with sea urchin eggs he found two distinct phases 

 of cytolysis which he terms "black cytolysis" and "white cytolysis. " 



With regard to the effect of the salts on the size of the yeast cells, 

 NaCl is the most and KC1 the least toxic, while CaCL and MgCL 

 stand midway. The effect is parallel with that of the multiplication 

 of cells. 



An experiment was carried on with a second culture of S. ellip- 

 soideus collected from another source by Cruess and named no. 60. 

 This experiment was also made in duplicate. With this yeast potas- 

 sium chloride and magnesium chloride gave the same results as with 

 no. 66, but NaCl and CaCL, showed a marked difference and CaCl 2 was 

 the most toxic of all. 4M NaCl gave an appreciable number of yeast 

 cells, while even .3M CaCL, stopped the growth altogether. Further, 

 the number of yeast cells was much lower than that of yeast no. 66. 

 Evidently yeast no. 60 was less vigorous than the other, though other- 

 wise there was no fundamental difference between them. 



