TfiE PERMEABILITY OF PROTOPLASM 117 



applying ether, toluene, and chloroform, in quantity to 

 plant cells is to kill them and render them permeable. 

 Thus, Giglioli (1911) drew attention to their effect, and 

 that of essential oils, upon transpiration of water from 

 leaves and upon the permeability of the yeast cell (1912). 

 Armstrong (1910) and his co-workers have shown that 

 under the influence of anaesthetics, and of certain sub- 

 stances termed by them hormones, actions take place 

 within the cells by which enzymes and their substrates 

 are brought into contact. Varied phenomena ensue, such 

 as liberation of hydrocyanic acid from certain glucosides, 

 and oxidations resulting in pigmentation. Dixon and 

 Atkins (1913, 1) also have found that anaesthetics greatly 

 increase permeability, for cell sap is much more readily 

 pressed out after their application. It must, however, 

 be considered whether these are toxic and irreversible, as 

 distinct from true anaesthetic effects, which are reversible. 



To decide this important question, Osterhout (1913, 1) 

 measured the resistance of tissue after exposure to anaes- 

 thetics. He found that very low concentrations of these 

 substances produce little or no effect, but a point is soon 

 reached at which a decided decrease of permeability occurs. 

 With still further increase in concentration this diminution 

 becomes more pronounced, and may be maintained for 

 several hours in presence of the anaesthetic. This change 

 of permeability is completely reversible and without injury 

 to the cells. 



If, however, a larger amount of anaesthetic be adminis- 

 tered, an additional decrease in permeability is observed. 

 This is followed by a rise to far above the normal, and if 

 the concentration be sufficiently high the increase con- 

 tinues till death supervenes. 



In these experiments it is seen that the decrease in per- 

 meability is easily reversible, whereas the increase is not. 



