CHEMICAL AGENTS ON CHROMATOPHORES 185 



9. The narcosis or depression of the pigment cells of trout by 

 the homologous alcohols corresponds very closely to their nar- 

 cotic action as determined by Overton and numerous other 

 investigators. 



10. Very dilute solutions of methyl, ethyl, and propyl alcohols 

 exert no action on the pigment cells of trout. 



11. The pigment cells of trout embryos respond to alcoholic 

 stimuli. Their mode of reaction is comparable to the reaction 

 of other tissues to alcohols inasmuch as they are stimulated by 

 small doses and depressed by large doses. 



12. Strychnine in moderate doses causes a primary con- 

 traction of the expanded melanophores. Large doses cause a 

 depression without a primar}^ stimulation (contraction). The 

 action of the strychnine is on the nervous system rather than 

 on the pigment cells directly. 



13. The action of picrotoxin causes a rapid contraction of 

 the pigment cells. The mechanism controlling the pigment 

 cells is in the higher centers, because if the spinal cord is severed 

 the. pigment cells expanded. 



14. Morphine induces a contraction of the melanophores in 

 isolated areas. This is probably due to the selective action of 

 morphine upon the nervous system. Large doses produce no 

 change in the expanded melanophores. Morphine expands the 

 pigment cells that were contracted in picrotoxin, KCl, and 

 strychnine. 



15. Curara causes a mixture of responses, that is, there are 

 areas of expanded and contracted melanophores. This is likely 

 due to the unequal action of the curara on the peripheral nervous 

 mechanism of the melanophores. 



16. Medium solutions of nicotine cause a contraction of the 

 pigment cells. Strong nicotine solutions have no effect on the 

 pigment cells. The action of nicotine is directly, on the nervous 

 controlling mechanism of the pigment cells. 



17. Atropine in all concentrations has no stimulating action 

 on the pigment cells of trout. Atropine paralyzes the fine nerve 

 connections of the pigment cells. 



