180 JOHN N. LOWE 



All the experiments show conclusively that atropine does not 

 have any direct stimulating action on the pigment cells of trout 

 embryos. Cushny ('10) says, that atropine acts on the higher 

 centers of the brain and less on the lower divisions, viz., the 

 medulla and the spinal cord, which is just the reverse of strych- 

 nine. This acts on the lower centers and not on the central 

 system. The results obtained justify the conclusion that the 

 pigment cells are controlled by the lower reflex centers. 



Romanes ('77) in his experiments on the medusae Sarsia (sp.) 

 and Tiaropsis found that atropine caused convulsive swimming 

 movements by a marked depression. Pickering ('93) showed that 

 0.012 gm. of atropine to 1 cc. of normal saline solution reduced 

 the normal heart beat of the embryonic heart of the chick. 

 Carlson ('06) found that atropine stimulated the heart ganglion 

 and not the muscle of the Limulus heart. Cushny ('10) says most 

 secretions are depressed by the administration of atropine. 

 This is not due to the inactivation of the secretory cells, but to 

 the failure of the nervous impulses. The action of atropine on 

 other tissues, from all evidence, shows us that it does not act 

 directly on the vascular and secretory elements, but on their 

 nerve terminations. It is therefore possible that atropine acts 

 on the pigment cells through their nerve fibers, paralyzing them, 

 but does not act directly on the pigment cells. 



8. Cocaine. One-half per cent solutions killed the trout em- 

 bryos rapidly. There was a momentary stimulation of the pig- 

 ment cells which was followed almost simultaneously by an 

 expansion of the pigment cells. In a 0.125 per cent solution of 

 cocaine the behavior of the pigment cells was the same as in the 

 0.5 per cent solution. In 0.025 per cent to 0.05 per cent cocaine 

 solution the pigment cells were contracted in four minutes. The 

 contraction was followed by an expansion. Solutions of 0.005 

 per cent of cocaine produced a complete contraction in five 

 minutes. The expansion followed in twelve minutes. Very 

 weak, 0.00033 per cent solutions, had no effect on the melano- 

 phores. 



These results show that cocaine has a primary stimulating 

 action on the pigment cells of trout embryos. This primary 



