THE PERMEABILITY OF PROTOPLASM 119 



external surface of the cell. The effect of various sugars, 

 before alluded to, has very probably an important bearing 

 on the translocation of these carbohydrates, and systematic 

 researches by the electrical method may go far towards 

 explaining the functions of the different members of this 

 group. 



Osterhout's researches have afforded very valuable in- 

 formation on this difficult branch of physiology, and have 

 demonstrated that the permeability of a tissue is a delicate 

 index of its vitality. The preservation of a normal degree 

 of permeability is, therefore, of the greatest importance to 

 every cell. 



As previously mentioned, anaesthetics increase the per- 

 meability of the protoplasm, thereby allowing the cell 

 solutes to be pressed out in the same proportion as that in 

 which they normally exist. The same effect is produced 

 by intense cold. From results obtained by chemical 

 analyses, Andre (1906 and 1907) concluded that the total 

 concentration, but not the relative proportions of the con- 

 stituents, of such expressed saps underwent alteration 

 during the application of the force. With this result the 

 experiments of Dixonand Atkins (1913, 1) are at variance, 

 for, instead of remaining constant, the ratio of the electrical 

 conductivity to the freezing-point of the sap was higher 

 in that from organs pressed direct than when obtained 

 from those rendered permeable by immersion in liquid air. 

 This demonstrates the greater permeability of the proto- 

 plasm to electrolytes, upon which the conductivity depends, 

 than to the solutes as a whole, including the sugars. The 

 conductivities recorded for the saps of treated tissues may 

 be slightly too low owing to the increased viscosity oc- 

 casioned by the sugars. This, however, could not reverse 

 the results, for Heald (1902) has shown t'hat the ash of 

 plant sap, when diluted to the correct concentration, 



