198 EEYNOLD A. SPAETH 



/, Innervation 



Tlie activity of vertebrate smooth muscle is normally con- 

 trolled through fibers of the sympathetic nervous system. Vol- 

 untary motor connections do not ordinarily occur. 



The innervation of the melanophores has been satisfactorily 

 demonstrated both histologically (Ballowitz '93) and physio- 

 logically (Pouchet 72 and '76, Von Frisch '11, Spaeth loc. cit.) 

 in several species of teleosts. v. Frisch has recently corroborated 

 and amplified the original observations of Pouchet, who first 

 claimed the innervation of the melanophores to be sympathetic. 

 1 have repeated the striking experiments of v. Frisch upon Phoxi- 

 nus with Fundulus. In this experiment one of the two branches 

 of the sympathetic system is severed immediately behind the 

 body cavity in the region of the haemal arch. Fish so treated 

 lose their power of color adaptation posterior to the point of 

 incision on the operated side, but continue to show normal motor 

 responses. Reciprocally, severing of the spinal cord eliminates 

 motor responses but, provided the operation has been carefully 

 performed, the sympathetic adaptations to difTerent colored bot- 

 toms remains normal. 



In Fundulus I have also found at the base of the medulla a 

 'contraction center' corresponding with that found by Lode 

 ('90) in the trout and by v. Frisch ('11) in Phoxinus. A light- 

 ening of the entire body of the fish follows the electrical stimula- 

 tion of this center. 



No satisfactory histological demonstrations of the nerve end- 

 ings in the melanophores of amphibians and reptiles have been 

 recorded. Bimmerman ('78), Biedermann, loc. cit. and more 

 recently Hooker ('12) have however, all demonstrated, physio- 

 logically, the sympathetic innervation in the melanophores of 

 the frog and Carlton ('04) has made similar observations in Ano- 

 lis. There is thus a very satisfactory unanimity of opinion on 

 this question. 



