A MICRO-ELECTRODE AND UNICELLULAR 



STIMULATION. 



I. H. HYDE.i 



During the summers of 1918 and 1919, while conducting ex- 

 periments on unicellular organisms and Echinoderm eggs, it was 

 found necessary to construct a micro-pipette that could be more 

 readily and more accurately controlled than could either Bar- 

 ber's 1 pipette or Chambers's 2 modification of the same. 



An apparatus was needed with which it was possible, not only 

 to inject definite amounts of fluid, and extract special parts of 

 cells, but also with which these could be electrically stimulated. 

 Such an apparatus was devised, and although it was only in the 

 process of being perfected, nevertheless with it, fluid could be 

 injected and the membrane and other parts of Echinoderm eggs 

 extracted, and these as well as unicellular organisms electrically 

 stimulated. It was possible, for instance, to stimulate different 

 parts of Vorticella, and to determine that the contractile sub- 

 stance of the stalk of this special species differed from the con- 

 tractile substance of the frog's striated muscle fibers, in that, it 

 did not follow the law of " All or Nothing," which was discov- 

 ered for these muscle cells by Pratt 4 with his very valuable and 

 interesting micro-electrode. The results pertaining to my ex- 

 periments with these devises will be published in the near future. 



At present only the micro-electrode, imperfect though it be, 

 shall be described, in the hope that it will be improved by some 

 one who has the opportunity and is interested in the experimental 

 fields requiring its use. 



The micro-electrodes are Barber pipettes, so modified as to be 

 employed for unipolar stimulation. They are glass tubes about 

 twelve centimeters long, six millimeters in diameter, and drawn 



1 From the Woods Hole Marine Biological Laboratory and the University 

 of Kansas. 



1 Barber, M. A., The Philippine Jr. Sc.. Sec. Trop. Med., 9, 307. 



2 Chambers, R., Am. Jr. Pliys.. 1910, p. 189: BIOL. BULL., 1918, 34, p. 121. 



3 Pratt. F.. Am. Jr. Pliys., 1917-1918-1919, Vol. 43. 44. 49. 



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