290 



Mr. S. G. Paine. 



[July 12, 



in oils. Of these, cadmium iodide is not soluble in oil or cholesterol, but is 

 known to form a double compound with lecithin ; trichloracetic acid was 

 found to dissolve with great readiness in both xylene and cholesterol. It 

 would, however, be unfair to assume from these facts that the presence 

 or absence of cholesterol and lecithin in the cells is the determining factor 

 for the diffusion of these substances. It seems to the author more likely 

 that there may be some characteristic of the molecule, or possibly a 

 determinate size of particle, which gives to certain substances the proper ty 

 of solubility both in oils and in living protoplasm. 



Diffusion must play a very important part in the technique of cytological 

 investigation, since proper fixation depends largely upon the rapid and 

 uniform diffusion of such agents as mercuric chloride, iodine, osmic and 

 chromic acids, etc. Variations in diffusion capacity may possibly account in 

 large measure for the differences observable under the influence of the 

 several fixing agents. It is conceivable, for instance, that in nuclear 

 investigations the extreme sharpness of definition with which the astral 

 rays and spindle-fibres have been brought out by some workers may be due 

 to inferior fixation ; in other words, to a contraction along lines of dynamic 

 activity, wherein the protoplasm has become so altered as to possess a 

 coefficient of penetrability for the special fixing agent employed which is 

 different from that of the surrounding medium. 



The primary object of this research has been to investigate the osmotic 

 behaviour of the yeast-cell towards those substances which have been 

 found to influence alcoholic fermentation. Harden and Young (9) have 

 shown that when phosphates, arsenites or arsenates are added to yeast-juice 

 and sugar a considerable increase of the rate of fermentation is produced. 

 When, however, these substances are applied to living yeast it has been 

 found that in almost all cases no such result occurs. Slator (10) has shown 

 that when neutral potassium phosphate is added to Jiving yeast the only 

 effect produced on the initial rate is that of a small inhibition. Iwanoff(ll) 

 on the contrary, and more recently Euler and Lundeqvist (17), have 

 demonstrated a small increase in the total fermentation produced by 

 addition of phosphates to living yeast and glucose, but these effects are not 

 comparable with that produced on yeast-juice. 



Another phenomenon of a similar character is observed in the case of 

 hexosephosphates, which are freely hydrolysed and fermented by yeast- 

 juice, but are scarcely affected by living yeast. As the formation and 

 decomposition of hexosephosphates plays an essential part in alcoholic 

 fermentation by yeast-juice, it is a matter of great importance to ascertain 

 whether these salts can penetrate the cell. 



