ACTIONS ON ENZYMES I09 



in a lipoid phase which is not upset by variation in either 

 polar or non-polar groups, and 2. that no structural spe- 

 cificity in the molecules is involved. It, therefore, seems 

 very improbable that adsorption at an interface is the 

 mode of action in the two instances of narcosis which 

 have just been given. Equally, it seems highly probable 

 that narcosis is produced in these two instances by the 

 production of a critical concentration of foreign molecules 

 in a bulk phase consisting mainly of hydrocarbon. 



At this point, we must ask the question, where is the 

 lipoid phase in the cell ? It may perhaps be the interior 

 of the cell membrane, the lipoid micelles, or possibly 

 a conglomeration of the hydrocarbon residues of protein. 

 Possibly all three sites may be involved in different in- 

 stances of narcosis. And no doubt there are some sites 

 which have not yet been thought of. 



It is important to note that this theory is not incom- 

 patible with the involvement of enzymes in narcotic 

 action. The action upon any of the three sites just men- 

 tioned may well produce an ultimate action upon the 

 degree of activity of an enzyme system. 



Theories Based on Actions on Enzymes 



We have previously noted that urethane acts upon de- 

 hydrogenases and will inhibit respiration for this reason. 

 But the linkage between respiration and other cellular 

 effects is complex, as is well illustrated by the fact the 



