MELANOPHORE A TYPE OF SMOOTH MUSCLE CELL 201 



tact or destroyed, a slight contraction of the melanophores is 

 usually induced" (p. 610), 



In the case of the reptilian melanophores Bert ('75) and Kruk- 

 enberg ('80) were able to corroborate the original observation of 

 Briicke ('52) who found that direct faradic stimulation of ex- 

 cised bits of dark skin in the chameleon produced a lightening, 

 i.e., a contraction of the melanophores. 



Thus the responses of several types of smooth muscle, as well 

 as of the melanophores, in representatives of all three groups of 

 lower vertebrates show a satisfactory agreement in their con- 

 traction to faradic stimulation. 



IV. Effect of Mechanical Siimulation 



By gently pinching or stretching excised pieces of frog or fish^ 

 stomach and oesophagus, powerful contractions may be induced, 

 which are reversible provided the stimulus has not been too vio- 

 lent. Precisely the same reaction follows a similar treatment of 

 portions of the skin of Loligo; the chromatophores expand widely. 

 I have verified this observation by Klemensiewicz loc. cit. and 

 all of the more recent investigations upon cephalopod chromato- 

 phores record a similar phenomenon in Loligo and other species. 



Fuchs (loc. cit) has called attention to the objection against 

 the expansion observed by many of the older investigators after 

 the surfaces of varios teleosts had been more or less violently 

 'stroked' with a needle. He says (p. 1432): ''Aus alien Beo- 

 bachtungen geht unstreitig hervor, dass einwandfreie Beobach- 

 tungen iiber die direkte mechanische Reizbarkeit der Fischchro- 

 matophoren nicht vorliegen." I have shown (loc. cit.) that by 

 selecting scales from the lateral portion of Fundulus where the 

 melanophores are relatively far apart, it is possible to stimulate 

 a single melanophore repeatedly by exerting a gentle pressure 

 with a fine, fire-polished glass needle. Great care must be exer- 

 cised not to rupture the delicate cells, for by so doing, the melanin 

 granules are scattered and produce the effect of an 'expansion' 

 recorded by the older observers. In this case it is certain that 



