292 



Mr. S. G. Paine. 



[July 12, 



cannot be taken as an explanation of the diffusion phenomena. A possible 

 solution of the problem has already been advanced (p. 289). 



It seemed desirable to ascertain whether these substances would act in a 

 similar manner towards the yeast-cell, it being at first thought that per- 

 manent plasmolysis of the cell might be taken as an indication that no 

 diffusion of the dissolved substance into the cell had occurred, an idea 

 which further experiments proved to be untenable (p. 294). The following 

 table contains the results of experiments with acetone, urea, mercuric 

 chloride, cadmium iodide, sulphuric and trichloracetic acids. Since the 

 volumes measured in the narrow tubes were very small, these experiments 

 were made on a larger scale ; 50 grm. of pressed yeast were stirred up with 

 50 c.c. of solutions of the various substances which Adrian Brown found to 

 be of interest. They were allowed to stand for varying lengths of time in 

 the cold room at a temperature ranging from —2° to +2°, and were then 

 all spun simultaneously in the centrifuge and the columns of residue and 

 liquid carefully measured. The corresponding volumes were ascertained by 

 gauging the capacity of the vessel. 



Table II. 



No. 



Solute. 



Percentage volume o: 



spun residue after 





"* 



2 hrs. 



3 hrs. 



4 hrs. 



20 hrs. 



25 hrs. 



176a 





43 -0 



41 -0 



36 -5 



37-0 



36 -5 



36 -5 



b 



Sodium chloride, molar ... 



43 -0 



43 -0 



45 -0 



43 -0 



40 -0 



40-0 





Trichloracetic acid, molar .. 



42 -0 



42-0 



37 -5 



37-5 



37 '5 



37 -5 



d 



Alcohol, 7 p c. (control) ... 



62 -0 



62 -0 



58 -0 



58 -0 



62 



60 -0 







64-0 



62 -0 



60 -0 



60 -0 



64 -0 



62-0 



f 

 9 





53 -0 



57 -0 



58 -0 



58 -0 



61 -0 



61-0 



Cadmium iodide, molar ... 



43 -0 



43 -0 



42 -0 



42 -0 



41-0 



41 -0 



h 



Mercuric chloride (satd.) . . . 



54-5 



50 -5 



50 "5 



43 -0 



38 "5 



35 -5 



These results exhibit striking differences when compared with Adrian 

 Brown's experiments. When this observer immersed dried grains of barley 

 in different solutions, water entered as freely and rapidly from solutions of 

 alcohol, acetone, and trichloracetic acid as from pure water, a fact which was 

 interpreted as showing that these substances readily penetrated through the 

 diffusion membrane. In cl and e. above alcohol of 7 per cent, and acetone 

 produced no permanent plasmolysis and would seem to diffuse quite readily. 

 Urea also produced no permanent plasmolysis, in striking contrast to Brown's 

 result, where the entrance of water was strongly inhibited. The behaviour 

 of trichloracetic acid also stands in contrast to its behaviour towards the 

 barley grain. 



