CHEMICAL AGENTS ON CHROMATOPHORES 



175 



animal was in the form of the letter S. The convulsive period 

 lasted a short time and gave from one to six spasmodic reactions. 

 The pigment cells remained contracted during this period. As 

 the convulsive tremors gave way to a complete paralysis the 

 pigment cells expanded. The convulsive period and the con- 

 traction of the pigment were simultaneous. Weak solutions of 

 0.0005 per cent had no effect on the trout embryos or their pig- 

 ment cells. 



If the embryos are removed from a 0.05 per cent caffeine citrate 

 solution during the period of convulsions, and if the poison is 

 washed out rapidly there is a complete recovery. The pigment 

 cells expand normally. If removed during paralysis after con- 



Showing a brook trout embryo in a typical caffeine convulsion 



vulsions the fish may recover very slowly or not at all. In 

 weaker solutions of 0.01 per cent to 0.025 per cent there are no 

 convulsions, but only a contraction of the pigment cells; there 

 is a complete recovery when they are placed in water. 



Carlson ('06) has shown that caffeine caused a primary aug- 

 mentation in the heart muscle and primary stimulation of the 

 heart ganglion of Limulus, Hedborn ('99) observed that caf- 

 feine stimulated the isolated mammalian heart (cat). Pickering 

 ('93) observed an increase in the number of heart beats in the 

 embryo chick's heart, and concluded from his work that it is 

 not necessary to introduce a nervous hypothesis to explam the 

 action of caffeine. Romanes ('77) has found in Sarsia (sp.) 

 exposed to a sea water saturated with caffeine there was a great 

 increase of the contraction and at the same time a diminution 



