IO8 RALPH S. LILLIE AND WARE CATTELL. 



to an error which may be considerable. In general the recorded 

 current density is greater than that to which the eggs were 

 actually exposed, since the current lines extend outside of the 

 rectangular vessel into the overflow. There is also an error of 

 measurement resulting from variability in the depth and contour 

 of the layer of water between the agar bridges; this condition 

 makes possible only an approximate estimate of the sectional 

 areas. The usual procedure was to measure the depth of the 

 water in the basket and on both sides of it and to calculate the 

 cross section from these measurements. But even during a single 

 5-minute experiment the water level often varied considerably, 

 sometimes because the eggs themselves clogged the silk bolting 

 cloth thus raising the level of water inside the basket. Again, 

 with regard to temperature, although the bulb of the thermometer 

 was completely immersed the irregularity of the water stream is a 

 source of uncertainty. Local temperatures may rise higher than 

 the average temperature recorded by the thermometer; or the 

 instrument may be actually registering the temperature of a 

 stream of water of greater or less velocity than that to which the 

 eggs are actually exposed. It may reasonably be assumed, 

 however, that on the whole the errors in opposite directions 

 compensate each other. 



It was thought possible that the physiological effect of the 

 current might be changed (increased or decreased) by changing 

 the balance of salts in the medium. This occurs, for example, in 

 the electrical stimulation of muscle. 1 Eggs were suspended in 

 pure isotonic NaCl solution (0.54 m), washed in this solution by 

 gentle centrifuging and decantation, and exposed to the current 

 (densities from 139 to 262 ma. /cm.) in the rectangular glass dishes 

 under the conditions already described. A certain degree of 

 activation results from the action of the pure NaCl solution in the 

 absence of the current. 2 The result of passing the current 

 through the NaCl solution containing the eggs was, however, 

 essentially negative; four out of eleven experiments showed a 

 slight increase in activation over that produced by the solution 

 alone, five showed no difference, while two showed a decrease. 



1 Cf. the observations of K. Lucas and G. W. Mines on the electrical stimulation 

 of muscle in Journ. Physiol., 1908, XXXVII., p. 459. 



2 Lillie, R. S., Amer. Journ. Physiol., 1911, XXVII., p. 289. 



