RALPH S. LILLIE 141 



dependent on variations in the condition of the surface film ; and it is 

 to be inferred, if the general conditions determining transmission are 

 similar in the Hving system and the metallic model, that the same is 

 true of the conducting protoplasmic strand or nerve fiber; i.e., that 

 the decrement-producing anesthetic acts by modifying the condition 

 of the protoplasmic surface film.i^ 



As Lucas and Adrian have pointed out, conduction with a decre- 

 ment is undoubtedly a physiologically normal phenomenon in many 

 regions of the central nervous system, as well as in the myoneural 

 junctions and other nerve endings and synapses. ^^ Whether a con- 

 ducting element or combination of elements in the living organism 

 transmits excitation in the "all or none" manner or with a decrement 

 depends not only upon its special peculiarities of structure or organi- 

 zation but also upon its physiological condition — state of metabolism, 

 fatigue, etc. — at the time. There is much independent evidence that 

 protoplasmic excitation and transmission are in general dependent 

 on local and transmitted alterations of the protoplasmic surface films 

 or plasma membranes under the influence of the local bioelectric cur- 

 rents accompanying activity. If this is true, conditions changing the 

 properties of these films must influence the whole behavior of the pro- 

 toplasmic system. The phenomena of anesthesia in particular seem 

 to afford many instances of this kind of correlation. ^^ 



In living animals the time relations of the recovery process in the 

 different irritable cells and tissues vary widely, and they usually 

 exhibit a close correlation with the time relations of the respective 

 excitation processes. In most cases recovery is more rapid in the 

 living tissue than in the passive iron model; yet this is not always the 

 case. In the photoreceptors of Mollusca recovery may require sev- 

 eral minutes, and in the smooth muscle of the mammalian ureter 

 Engelmann found under some conditions imperfect transmission for 

 15 seconds or more after the passage of a contraction wave.^^ The 



^^ The evidence that the anesthetic acts primarily upon the plasma membrane 

 of cells is summarized in my review, The theory of anaesthesia (Lillie, R. S., 

 Biol. Bull., 1916, XXX, 352). 



^^ Lucas, K., Conduction of the nervous impulse. New York, 1917, Chapters 

 X and XIII. 



15 Engehnann, T. W., Arch. ges. Physiol., 1869, ii, 271. 



