EMULSION-STRUCTURE OF PROTOPLASM 293 



be the consequence. This may be seen by reference to the diagram 

 in Fig. 16. 



It should be borne in mind that the existence of funnel-shaped pores 

 in the surface of a cell or in a membrane would only give rise to one- 

 sided permeability provided the diameter of the pore at the constricted 

 end were comparable with the mean free path of the penetrating mole- 

 cules. Were the least diameter of the pores less than the mean free 

 path of the pentrating molecule, then the membrane would be a strictly 

 semipermeable membrane for this type of molecule. Were the least 

 diameter of the pores on the contrary, very large in comparison with 

 the mean free path of the molecule concerned, then the membrane 

 would be freely permeable by this molecule in either direction. Thus 

 it is readily conceivable that membranes of this type might exhibit 

 One-sided Permeability for certain substances dissolved in water, 

 Absolute Permeability for others, and Semipermeability for yet other 

 molecules. 



On the other hand, if the above sketch represents truly the structure 

 of the superficial layer of cells, substances which are soluble in fats 

 would enter the cell through the radiating columns of lipoidal material. 

 Now the phenomenon of one-sided permeability has not as yet been 

 observed to be displayed toward substances which are soluble in 

 lipoids. Indeed, in general, the penetrability of cells by substances 

 which are soluble in lipoids is very much greater than their penetra- 

 bility by other substances, no matter how soluble they may be in water. 

 This fact is very strikingly illustrated by the experiments of Overton 

 and Meyer, who measured the minimal concentrations of various 

 Narcotics dissolved in water which would induce narcosis in tadpoles, 

 the narcosis being evidenced by cessation of movement. The same 

 narcotics were dissolved in water and the water shaken up in Olive 

 Oil and the relative solubilities of the narcotics in water and in oil 

 estimated by the distribution of the narcotic between the two solvents. 

 The following were illustrative results obtained with various Alcohols : 



Solubility in water. 



Narcotic. molecules per liter. Solubility in oil. 



Methyl alcohol . . . . 0.52-0.62 Solubility in water = OC solublein50 



parts of oil. 



Ethyl alcohol .... 0.27-0.31 30 : 1 



Propyl alcohol .... 0.11 8:1 



Butyl alcohol .... 0.038 Soluble in 12 parts of solubility in 



water; oil = OC . 



Caprylic alcohol . . . 0.0004 Soluble in 2000 parts of solubility in 



water; oil = (X . 



The following results were obtained with other narcotics: 



' Solubility in oil. 



Critical concentration. Solubility in water. 



Narcotic. . ------ - -- - - 



At 3. At 30. At 3. At 30. 



Salicylamide .... Vwoo i/ 600 22.232 14.002 



Benzamide ..... l /5oo Yaoo 0.672 0.437 



Monacetin ..... Vo l /io 0.099 0.066 



Ethyl alcohol ..*../ V 0-026 0.047 



Chloral hydrate . . . VBO V*o 0.053 0.236 



Acetone ...... J /3 VT 0.146 0.235 



