178 JOHN N. LOWE 



and even a complete arrest. Plateau ('80) found that curara 

 did not modify the frequency of the amplitude of the Decapod 

 heart. Larger doses diminished the amplitude. Dogiel (77) 

 showed there was a primary stimulation by curara of the heart 

 of Corethra plumicornis. Boehm and Tillie ('04) have observed 

 a primary stimulation of the isolated mammalian heart (dog). 



Since Curara stimulates the central nervous system Cushny 

 ('10) and other ganglia Carlson ('06), it is possible that it acts 

 as a stimulant on the medulla and spinal cord which transmit 

 the impulse to the chromatophores, and a contraction results. 

 Later as the curara destroys the nerve end plates the stimulus 

 does not reach the pigment cell from the center. The pigment 

 cells retain their independent irritabihty lor a long time. The 

 mixture of contracted and expanded melanophores is probably 

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

 mechanism of the melanophores. 



6. Nicotine. When trout embryos were exposed to 0.5 per cent 

 nicotine solution, their muscles twitched for a moment and then 

 all activity ceased. The heart beat continued for twenty-eight 

 minutes. There was no change in the pigment cells. The pig- 

 ment cells disintegrated soon after death. There was a very 

 marked maceration of all the tissues. The whole fish was cov- 

 ered by a colorless shme. In a 0.125 per cent nicotine solution 

 there was a slight primary contraction of the melanophores 

 which was followed almost simultaneously by an expansion. 

 The eyes bulged out of the head which caused the fish to ap- 

 pear grotesque. A 0.005 per cent solution of nicotine caused a 

 complete contraction of the pigment cells in two and one-half 

 minutes. The paralytic expansion occurred eight minutes after 

 the contraction. In 0.0025 per cent nicotine the contraction 

 time was the same as in the preceding experiment. The period 

 of paralysis was delayed which occurred in eleven minutes. A 

 nicotine solution of 0.0005 per cent produced a complete con- 

 traction in eleven minutes. The paralysis or depression of the 

 pigment cells appeared in thirty-five minutes. In a 0.0001 per 

 cent nicotine solution there occurred only a very slight change 

 in the form of the pigment cells. In diluted 0.00005 per cent 



