170 



JOHN N. LOWE 



decrease its irritability; 2) on the nerve endings leading from the 

 ganglia controlling the pigment cells; 3) on the central nervous 

 system. I have no direct evidence to offer which will enable us 

 to determine which of these or combination of these three fac- 

 tors are operative in the action of the drugs on the pigment 

 cell, for I was unable to separate the nervous and pigment cell 

 tissues for experimental purposes. It is obvious that large 

 doses have no selective action. At certain optimal concentra- 

 tions all the drugs show a selective action on the pigment cells 

 or their controlling mechanism. This selective action of drugs 

 on the mechanisms of the pigment cells will further our knowl- 

 edge as to their function. v 



Fig. 1 A normal' brook trout embryo showing the general alignment of the 

 body. 



In interpreting my results I have given special emphasis to 

 their relation in a comparative way to the observations of other 

 observers on various vertebrate and invertebrate tissues. This 

 comparative method makes the results easier of interpretation 

 and is less liable to lead to an erroneous conclusion. 



The drugs used were all of Merck's manufacture. They were 

 dissolved in oxygenated distilled water. The stock solutions 

 were made up from 0.25 per cent to 0.5 per cent. Dilutions were 

 made from these solutions. The experiments were carried on in 

 Syracuse watch glasses in 10 cc. of the solution. These re- 

 sults were checked by experiments in small stender dishes of 

 50 cc. capacity. The conclusions are based on experiments re- 

 peated ten times in 1913 and again in 1914 another series of ten 

 was tried. Five to ten animals were used at one time in each 

 dilution. The trout embryos used were from four days to two 

 weeks after hatching. In no case were the individuals of the 

 different ages mixed. 



* Figures 1, 2, and 3 were drawn by Miss H. J. Wakeman. 



