MELANOPHORE A TYPE OF SMOOTH MUSCLE CELL 207 



the contractions between expansions are incomplete, the reduc- 

 tion being in this case in the contractions. The disappearance 

 of the pulsations leaves the melanophores expanded instead of 

 contracted. We may therefore say that the melanophores may 

 recover after having been contracted in BaCL, provided the time 

 of immersion in the BaCL has not been more than about five 

 minutes (fig. 2). 



Automatic pulsations or rhythmic contractions occur not un- 

 commonly in several types of smooth muscle. Among the lower 

 vertebrates, for example, Schultz (1. c.) has described this phe- 

 nomenon in ring preparations of the stomach of the frog and 

 Stiles ('01) has studied it in similar preparations of the frog's 

 oesophagus. An examination of their figures shows that the 

 rapidity and frequency of the contractions is not unlike those 

 occurring in the melanophore after having been treated with 

 BaCl2 and returned to NaCl. 



B. Organic Substances. Krukenberg ('80) carried out a series 

 of experiments upon the reactions of the chromatophores of Ele- 

 dona, a cephalopod, to organic substances. He found that 5 

 per cent ethyl alcohol, ether and chloroform (strength not stated 

 in either case) produced a contraction of the radial smooth mus- 

 cles i.e. an expansion of the chromatophores. When pieces of 

 the skin were washed or returned to sea-w^ater, the chromato- 

 phores contracted and regained their irritability. Klemensie- 

 wiecz ('78) observed a lightening of the skin in Loligo and Eledona 

 when subjected to vapors of amyl nitrite. The chromatophores 

 in isolated pieces of skin showed the same reaction. Amyl ni- 

 trite is a familiar vaso-dilator. The relaxation of the radial 

 muscles in the chromatophores of cephalopods therefore sug- 

 gests that this may be a typical response for physiologically 

 widely differing varieties of smooth muscle. 



I have exposed the melanophores of Fundulus to alcohol, 

 ether and chloroform vapors. The scales bearing these melano- 

 phores were placed upon glass slides and just covered with Ring- 

 er's solution. The slides w^ere then placed over Syracuse glasses 

 containing the organic fluid to be tested and both were covered 

 with small, ground-edged, bell jars and sealed with vaseline. 



