MICRURGY 



55 



The cell contains electrolytes which, being unequally distributed, 

 must give rise to potential differences in the cell. It is such 

 potentials which micrurgists have attempted to measure. 

 There is also a potential between one cell and another in tissue 

 and between the interior of a cell and its surrounding fluid. 

 The results of such attempts we shall learn later. Here we 

 are concerned with how they were made. 



Fig. 42. — Agarpipette electrode with calomel cell of Ettisch and Peterfi. 



Among the first microelectrodes was that of Ettiscli and 

 Peterfi. It consisted of a micropipette (fine capillary) filled 

 with agar, or gelatin, saturated with a solution of potassium 

 chloride which served as the conducting medium for the feeble 

 electric current (Fig. 42). Electrical connection with an instru- 

 ment (galvanometer) for detecting the presence of the current 

 was made through a small calomel cell. Agar dissolved in an 

 aqueous solution of an electrolyte and of such concentration 



^ 



Fig. 43. — Micromagnet of Taylor. 



(2 per cent) as to set to a gel is used instead of a wire to make 

 contact within the cell, because metals bring about electrical 

 disturbances which may give rise to potentials that are not 

 normally present in the cell (as do zinc and copper strips when 

 put into an electrolytic solution). Among the metals, platinum 

 is the least objectionable. A neat addition to micrurgical 

 tools is the micromagnet designed by Taylor. The figure 



