12 CELLULAR 



enter the cell, while lipoid-soluble dyes pene- 

 trate readily. 



3. Organic substances (including such anes- 

 thetics as ether and chloroform) penetrate and 

 affect the cell the more readily the more soluble 

 they are in lipoid. 



Overton's hypothesis has been a very valuable 

 stimulus to investigation but it has become in- 

 creasingly evident that satisfactory progress is 

 impossible without more accurate measurements 

 and a number of attempts have been made to 

 provide suitable methods. It is evident that the 

 best procedure is to expose the cell for a suitable 

 time to a solution and then to analyze the cell- 

 contents to discover what has penetrated. This is 

 beset by difficulties which investigators have 

 sought to overcome in various ways. 

 ''^ Some have made analyses of tissues, but it is 

 evident that these must include too much inter- 

 cellular material to be satisfactory. Analysis of 

 the solution bathing the tissue in order to deter- 

 mine what is absorbed, is open to the objection 

 that substances collect on the surfaces of cells, as 

 well as in the cell walls and in the spaces be- 



