CONDUCTIVITY AND PERMEABILITY 229 



that the penetration of dyes is dependent on their solu- 

 bility in lipoid. Subsequent investigations have brought 

 to light so many exceptions to this rule that it can no 

 longer be regarded as conclusive evidence in favor of 

 Overton 's views. 53 



Overton 's views gained wide support through their 

 application to the explanation of narcosis. Overton 54 and 

 Meyer 55 independently arrived at the conclusion that the 

 more soluble a substance is in lipoid, the more effective it 

 is as a narcotic. They explained this by saying that the 

 more soluble the anesthetic is in lipoid, the more easily it 

 penetrates the lipoid membrane. 



Although this hypothesis has found wide acceptance, 

 there are serious objections to it. 



If it be true that anesthetics are generally effective in 

 proportion to their solubility in lipoid, 56 it does not by any 

 means follow that the plasma membrane is lipoid. As 

 we have already seen, 57 the effectiveness of a dye in color- 

 ing the cell does not depend on its rate of penetration, but 

 on its ability to accumulate within the cell by combining 

 with substances in the protoplasm. If this is also the 

 case with anesthetics, lipoids in the interior of the cell 

 may be the determining factor, and there is no necessity 

 for the assumption of a lipoid membrane. 



It is not the desire of the writer to enter into further 



^Hober (1914) 426 ff. Also p. 645; Kiister (1911) Ruhland (1912, 

 A, B) ; Schulemann (1912) ; Goldman (1912) ; Garmus (1912) ; Robertson 

 (1908); Kite (1913); Ruhland (1909). 



54 Overton (1901). 



65 Meyer (1899). 



M There are some substances which act as anesthetics ( e.g., magnesium 

 salts) which are only slightly soluble in lipoid. 



67 See page 210. 



