1911.] 



The Permeability of the Yeast-Cell. 



301 



were suspended in distilled water and the mixture centrifuged, only a faint 

 trace of milkiness was produced by the addition of acid silver nitrate to the 

 liquid poured off. 



These results show that the diffusion of sodium chloride is slow. A 

 definite quantity of substance enters the cell when yeast is suspended 

 in M/10 sodium chloride solution and allowed to stand over night, although 

 no diffusion is noticed after a suspension of three hours only. 



Ammonium Sulphate. 

 The next experiments were made with ammonium sulphate, as being a 

 substance which is of service to the yeast, and which is a sufficient source 

 of nitrogen in artificial culture. In these experiments two concentrations of 

 the solution have been employed, of approximately one-tenth and three- 

 tenths molar respectively. 



Table VIII. 



No. 



Conditions. 





Liquid. 



Yeast. 



P. 





K. 





Initial. 



Final. 



Initial. 



Final. 



67 



Stood 20 lirs. in cold store. 

 Solution, '1 molar 



Total 



(NH 4 ) 2 S0 4 



100 -40 

 1-31 



97'84 

 1 '21 



50 -00 

 nil 



52 -56 



o-io 



0-28 



1 -26 



0-22 



68 



Stood 20 hrs. in cold store. 

 Solution, O'l molar 



Total 



(NH 4 ) 2 S0 4 



100 '50 

 1-31 



99 -21 

 1-19 



50 -00 

 nil 



51 -29 

 0-12 



0-34 



1-22 



0-28 



69 



Stood 3 hrs. in cold store. 

 Solution O'l molar 



Total i 

 (NH 4 ).,S0 4 



100 '60 

 1-29 



97 -30 

 1 -23 



100 -oo 



nil 



103 -30 

 0-06 



0-09 



1-28 



0'07 



70 



Stood 3 hrs. at room tem- 

 perature. Solution, O'l 

 molar 



Total 



(NH 4 ) 2 S0 4 



100 -60 

 1 '31 



99 -48 

 1 -21 



50 -00 

 nil 



51 -12 

 0-10 



0-28 



1 -24 



0-23 



71 



Stood 3 hrs. at room tem- 

 perature. Solution, O'l 

 molar 



Total . . , 

 (NH 4 ) 2 S0 4 



100 -60 

 1-31 



102 -50 

 1 -28 



50 -00 



nil 



48-10 

 0-03 



0-09 



1-27 



0-07 



145 



Stood 20 hrs. in cold store. 

 Solution, O'l molar. Air- 

 dried yeast 



Total ,,, 

 (NH 4 ) 2 S0 4 



90'10 

 1-14 



58 -78 

 0-98 



30 -00 

 nil 



61 -32 

 0-16 



0-37 



1-76 



0-22 



149 



Stood 20 hrs. in cold store. 

 Solution, 0'3 molar 



Total . ,, 

 (NH 4 ) 2 S0 4 



50 '50 

 1-84 



58 -87 

 1-71 



50 -00 

 nil 



41 -63 

 0'13 



0-47 



3-00 



0-15 



150 



Stood 20 hrs. in cold store. 

 Solution, 0'3 molar. Air- 

 dried yeast 



Total 



(NH 4 ) 2 S0 4 



100 -oo 

 3-65 



90 -86 

 3-40 



50 -00 

 nil 



59'14 

 0-25 



0-61 



3-91 



0-16 



151 



Stood 20 hrs. in cold store. 

 Solution, 0'3 molar. Air- 

 dried yeast 



Total 



(NH 4 ) 2 S0 4 



100 -00 

 3-65 



75 -44 

 3-13 



50 -00 

 nil 



74 -56 



1 -03 



4-41 



0-23 



