MELANOPHORE A TYPE OF SMOOTH MUSCLE CELL 203 



control may be simultaneously and effectively eliminated. The 

 objection may be raised that even in excised pieces of the animal 

 it is impossible to destroy the ultimate nerve terminations, hence 

 we are unable to state with certainty that the effect is a direct 

 one and not transmitted throug;h the cut stumps of the sympa- 

 thetic nerves which remain in such a preparation. I have else- 

 where (loc. cit.) adduced evidence to show that this objection is 

 certainly invalid in the case of the isolated melanophores of the 

 scales of Fundulus. 1 shall limit the following discussion of the 

 reactions of melanophores to chemical stimuli to cases which are 

 as nearly as possible comparable to the chemical stimulation of 

 isolated smooth muscle. 



A. Inorganic Substances. Schultz ('97) observed that dis- 

 tilled water acted as a weak contracting stimulus in opened ring 

 preparations of the stomach of the frog. Meigs ('10) has shown 

 that distilled water gives a typical curve of contraction in prepa- 

 rations of longitudinal strips of the frog's stomach. 



I have found (loc. cit.) that the melanophores of Fundulus 

 slowly contract when brought from the living dark fish or from 

 0.1 N NaCl to distilled water (fig. 1). 



Schultz (1. c.) noted a relaxation and swelling of the smooth 

 muscle of the frog's stomach in 10 per cent NaCl solution. Meigs 

 (loc. cit.) has shown that in solutions of KCl, the stomach muscle 

 of the frog (R. pipiens) slowly contracts and loses weight while 

 in NaCl it elongates and aborbs water. ^ I have observed that 

 the chromatophores in pieces of the mantle of Loligo expand im- 

 mediately upon being immersed in 0.1 N KCl solution. This is 

 obviously due to a contraction of the radial smooth muscles. 

 Furthermore, provided the exposure to KCl has not been too 

 long, when such chromatophores are returned to 0.1 N NaCl or 

 better, Ringer solution, they contract again, the radial muscles 

 are relaxed. 



The melanophores of all the species of teleosts with which I 

 have experimented, showed a contraction in 0.1 N KCl solution 

 and an expansion or relaxation in 0.1 N NaCl, dilute sea-water, 



* Zoethout ('02) found that KCl produced a contraction in the gastrocnemius 

 of the frog and NaCl a relaxation. 



THE JOURNAL OF EXPERIMENTAT. ZOOLOGY, VOL. 20, NO. 2 



