176 JOHN N. LOWE 



of the potency of the beat. Soon the pulsations became of a 

 fluttering nature and spontaneous movements ceased. 



In the pigment cells of trout there is a stimulation which is 

 at its height during the convulsive period. This is soon followed 

 by a paralysis and an expansion of the pigment cells results. 

 There is a direct resemblance in the results obtained with caffeine 

 and strychnine, in that the reflex irritability is remarkably in- 

 creased. The pigment cells contract in both instances during the 

 convulsive period. There is a similarity in the results on the 

 pigment cells of trout and the work of other investigators on 

 other tissues. Caffeine may act directly on the pigment cells as 

 it does on muscle (Pickering, '93, Carlson, '06), or it may 

 stimulate the reflex centers in the medulla and spinal cord, 

 which give off the fibers which control the pigment cells. 



■5. Curara. In very strong solutions of curara of 2 per cent 

 to 1 per cent, a few pigment cells contracted. When trout em- 

 bryos were exposed to a 0.5 per cent solution they moved about 

 rapidly for eight to ten minutes. In one case one showed a 

 complete contraction of the melanophores in three minutes 

 while the other nine fish in the same lot showed no change. 

 The one that showed this contraction had its pigment cells com- 

 pletely expanded in thirteen minutes. In 0.25 per cent solution 

 there occurred a partial contraction of the pigment cells. The 

 pigment cells along the lateral line were not contracted. The 

 fish died in an hour and were covered with a colorless jelly- 

 like slime. In the following dilutions of curara, viz., 0.05 per 

 cent, 0.025 per cent and 0.001 per cent a partial contraction of 

 the pigment cells occurred in two minutes and thirty seconds. 

 In a 0.0025 per cent curara solution the change took place in 

 fourteen to forty minutes. In all the experiments the contrac- 

 tion of the pigment cells was not evenly distributed but occurred 

 in spots (fig. 15). The tail portion showed many contracted 

 pigment cells, but in the head region there were the largest num- 

 ber of contracted melanophores. Along the lateral line the pig- 

 ment cells remained expanded. After fourteen or fifteen min- 

 utes all the contracted pigment cells were expanded. This 

 mixture of responses was constant for all the experiments. 



