CHEMICAL AGENTS ON CHROMATOPHORES 



169 



an important part in their action. It was observed that the 

 greater the dielectric constant of the alcohols used the lower the 

 stimulating or depressing power, and conversely the lower the 

 dielectric constant the more striking were the reactions. What- 

 ever may be the relation of these physical factors of the alco- 

 hols in stimulation or depression, their chemical structure must 

 not be overlooked ; for as the length and complexity of the chain 

 in monohydric alcohols increases so does the 'strength of their 

 action. 



Reactions to alkaloids 



The study of the action of drugs on the pigment cells of trout 

 was undertaken with a threefold purpose, viz., to compare the 

 action of drugs on the pigment cells with that of other tissues; 

 second, to determine if possible the controlling mechanism of the 

 pigment cells, and third, to see if the drugs had a specific action 

 on the pigment cells. 



The literature on the pharmacology of the pigment cells of fish 

 is not very extensive. The earliest historical record of experi- 

 ments on the action of drugs on the pigment cells is that of Redi 

 (1664), who observed that eels which died in a tobacco decoction 

 were light in color. Pouchet (76) observed that Gobius niger 

 changed in color when placed in strychnine. Morphine, qui- 

 nine, and santonin had no effect. Lode ('90) concluded that 

 curare destroyed the nerve endings of the pigments cells of 

 trout (Salmo fario). von Frisch ('11) found that chloral hy- 

 drate contracted the pigment cells of the minnow and crucion. 

 He also concluded that the action of cocaine was through the 

 central nervous system. 



The pigment cell may be stimulated or depressed by the drug 

 acting: 1) on the pigment cell in such a way as to increase or 



