cox AND OTHERS: ELECTRIC TISSUE 497 



The charge passing through 1 cm.^ of electroplax layer is found by 

 dividing q by the cross-sectional area of the electric organs. (The 

 measurements were made at the anterior end, where the cross-section 

 is nearly uniform.) Since the fish on which the measurements were 

 made were not killed, the cross-section had to be determined indirectly 

 from external measurements. Two methods were employed. In the 

 first method, the girth of the fish was measured. The cross-section of 

 the organs was then estimated by comparison with measurements on 

 dissected fish, on the assumption that the cross-section of the organs 

 bears a constant ratio to the square of the girth. In the second 

 method, a simple mechanical device was employed to trace the outline 

 of the cross-section of the live fish. The area enclosed by this outline 

 was measured, and the cross-section of the organs was taken as 59 per 

 cent of the total area, this percentage having been obtained from meas- 

 urements on a number of dissected specimens. When both methods 

 were used, the agreement between the results was fairly good, the 

 values determined by the two methods showing a mean deviation of 

 around eight per cent. 



(However, the use of only the first method, in another experiment, 

 led to a rather serious error." The number used then as the ratio of 

 the cross-sectional area of the organs to the square of the girth of the 

 fish was obtained from measurements on only two specimens. Also, 

 the girth of these sections was not measured in the same way as on the 

 live fish, and this led to a further discrepancy, which was increased 

 when the girth was squared. The correction of the resulting error to 

 accord with our new measurements on a larger number of specimens 

 requires that the values of electric energy per gm. and impulse given 

 in the paper referred to should be reduced about 40 per cent. Instead 

 of inferring, as we did in a subsequent paper,^ that the total electric 

 energy is about equal to that of the breakdown of phosphocreatine and 

 the production of lactic acid, we should now infer that the electric 

 energy is about six tenths of the sum of the energies of these two chem- 

 ical processes. The correction brings this result into fair agreement 

 with that reported by Nachmansohn, elsewhere in this volume.) 



The electromotive force of the part of the organs included between 

 the electrodes was determined by the point of intersection of the volt- 

 age-current graphs. This quantity was divided by the distance be- 

 tween the elctrodes, to give the electromotive force per cm. along the 

 column of electroplax layers. The product of the electromotive force 

 per cm., regarded as constant during the impulse, by the charge travers- 

 ing one cm.^ of electroplax layer, is the total electric energy per cm.^ 

 produced in one impulse. 



