Response of Single Cells to Stimulation. 



199 



113 ("77) 



The response of single cells to electrical stimulation. 



By R. A. Spaeth. (By invitation.) 



[From the Osborn Zoological Laboratory, Yale University, New 



Haven.] 



There is an accumulation of embryological, morphological and 

 physiological evidence at hand showing that the melanophores of 

 vertebrates are to be considered highly modified smooth muscles 

 cells. By means of a simple recording device the responses of 

 single melanophores of Fundulus heteroclitus to faradic and gal- 

 vanic stimulation have been studied in some detail. 



In faradic stimulation it appears that as regards the duration 

 of the latent period, the quantity of current necessary to bring 

 about a response in the cell, the increased height of the contraction 

 curve with an increase in the strength of stimulus and the develop- 

 ment of tetanus by properly spaced single break shocks, the con- 

 traction curves for a single melanophore show a striking resem- 

 blance to smooth muscle graphs obtained from the bladder of the 

 cat (Stewart) and the stomach of the frog (Howell). 



A constant current, which has previously been supposed to 

 produce an expansion of the melanophores, causes a contraction 

 when applied through non-polarizable electrodes of the Zn-ZnSC>4 

 type. An expansion of the melanophores may be produced by 

 galvanic stimulation if platinum electrodes are used but this has 

 been shown to be due to hydroxyl ions liberated at the cathode. 

 Both the make and the flow of the constant current are effective 

 contracting stimuli. With currents of moderate strength there 

 is, at first, a rapid rise in the contraction curve due to the combined 

 effects of make and flow but subsequently a partial falling off of 

 the contraction giving a typical plateau. Stewart has found 

 precisely the same conditions in the bladder of the cat. No 

 response to the breaking of the constant current has thus far been 

 observed in the melanophore. 



The evidence obtained from these experiments with the re- 

 sponses of single melanophores to electrical stimulation, appears 

 to strengthen and corroborate the writer's contention that in the 



