70 SENESCENCE AND REJUVENESCENCE 



is due to changes in the colloid substratum. According to Traube 

 the narcotics act by decreasing surface tension and so increasing 

 the degree of aggregation of the cell colloids, and decrease in oxida- 

 tion or in metabolism in general results from this change in aggre- 

 gate condition. Other factors may play a part in certain cases, 

 but Traube has shown that a relation exists in many cases between 

 the decrease in the surface tension of water by narcotic substances 

 and their narcotic power, and that narcotic concentrations of 

 many different substances are isocapillary, i.e., decrease surface 

 tension by the same amount. Warburg has shown that a close 

 interrelation exists between the oxidations in the cell and the funda- 

 mental structure and that, at least in many cases, the narcotics de- 

 crease oxidation. He concludes, in essential agreement with 

 Traube, that the narcotics act by altering surface tension and so 

 produce capillary changes, particularly in the lipoids. 



The lipoid theory of Meyer and Overton and their followers 

 and Traube's surface tension theory differ from Verworn's asphyxi- 

 ation theory in that they regard the decrease in metabolic activity 

 in narcosis as resulting from or associated with the changes in the 

 colloid substratum of the cell. The unsatisfactory character of 

 purely or pre-eminently chemical theories of the organism has 

 been pointed out in chap, i, and it seems probable that in narcosis 

 as well as in other changes in chemical activity in the organism, 

 the substratum and the changes which occur in it must be taken 

 into account. It seems not improbable, moreover, that narcosis 

 is not always produced in exactly the same way. Irritability, as 

 Winterstein suggests, probably depends upon the maintenance of 

 a complex dynamic equilibrium of some sort, and this equilibrium 

 may be destroyed with a resulting loss of irritability, by changes of 

 various kinds in the cell. It is even conceivable that in some cases 

 the change may concern primarily or chiefly the substratum, and 

 in other cases the chemical reactions, or certain of them, and we 

 must admit the further possibility that both the substratal and the 

 chemical changes may differ with different narcotic substances 

 and yet produce much the same general result as regards irrita- 

 bility. Various observations show that very considerable differ- 

 ences do exist in different forms of narcosis. It was noted above 



