48 



sterin, the number of the sterin molecules being too small and no 

 specific affinity being known to exist between sterin and the dye. 

 We can expect the sterin molecules to build water structures with a 

 cubic lattice around themselves and it is reasonable to assume that 

 the long life of the excitation is due to the interaction of the ex- 

 cited molecules and their electrons with this cortisone- water system. 

 Chloroform is very sparingly soluble in water (0.014 Af). All 

 the same if %o p^rt of a saturated watery solution is added to the 

 cortisone-dye solution, no long-life phosphorescence will be ob- 

 served on freezing, although the light emission remained in- 

 creased, in spite of the presence of the narcotic. It is reasonable to 

 assume that the hydrophobic steroid attracted the chloroform 

 molecules which modified its relation to water and modified 

 with it the water structures responsible for the lengthening of the 

 lifetime of the excited dye molecules. Since the concentration of 

 the chloroform in our system was very low, 3.10"* Al or less, it is 

 conceivable that this narcotic inhibits the functions of the central 

 nervous system in vivo by interfering Vv'ith the interrelation of 

 lipids and water, disturbing herewith £* and, possibly, shortening 

 the lifetime of excitations. The total abolition of the long-life 

 phosphorescence is the extreme of an action in this direction. Less 

 drastic actions may lead to subtler changes and may be responsible 

 for the great variation in symptoms produced in the central nerv- 

 ous system by different drugs. In the earlier chapters of this book 

 we considered only direct interactions between two substances A* 

 and B. It seems likely that for an understanding of drug actions an 

 indirect interaction will also have to be considered in analog}' with 

 the above experiment with acridine orange, cortisone, and chloro- 

 form, in which the drug did not seem to act directly on the dye, 

 but seemed to act by modifying the relations of a third substance 

 to water. Naturally, this does not preclude that the excited mole- 

 cules themselves should be also directly influenced by a narcotic, 

 if they have an affinity for it. Rhodamin B has such an affinity, as 

 shown by the fact that it can be shaken out from water with chloro- 



