CHEMICAL AGENTS ON CHROMATOPHORES 



171 



Other experiments are in progress to determine the action of 

 drugs on pigment cells isolated from the nervous system. 



1. Strychnine. In 0.5 per cent oxygenated solution death re- 

 sulted without primary stimulation of the pigment cells. In 

 0.05 per cent strychnine solution the results were the same. 

 Solutions of 0.005 per cent strychnine caused a contraction of the 

 pigment cells rapidly, the contraction was complete in five min- 

 utes. There was a remarkable thing observed in this concen- 

 tration of strychnine. The irritability of the fish was increased 

 to a high degree. The fish went into typical strychnine spasms. 

 The head was thrown backward and the tail curved upward and 

 forward, describing a half circle (as shown in text fig. 2). A 



Fig. 2 Showing a brook trout embryo in a typical opisthotonos response in 

 0.005 per cent strychnine. 



passing shadow over the disk brought on a new spasm. Shadows 

 in rapid succession increased the concavity backward. If the dish 

 was tapped very lightly the same responses occurred. This 

 period of heightened excitability lasted from eight to twelve 

 minutes. During this interval the pigment cells remained con- 

 tracted (fig. 13). As this convulsive period disappeared, the pig- 

 ment cells expanded (fig. 14). This expansion showed that the 

 depression and paralysis of the pigment cell controlling mecha- 

 nism had occurred. In 0.0005 per cent the pigment cells were 

 contracted in ten minutes. No convulsions were observed in this 

 concentration. In weak solutions of 0.00005 per cent to 0.000025 

 per cent no contractions of the melanophores was produced. 



