464 ELECTRO-PHYSIOLOGY CHAP. 



increases with the size of the fish (whether proportionately re- 

 mains, as Hermann pointed out, 14, p. 486, an open question), 

 while the number of the prisms (or plates) is unaltered, a direct 

 relation between the diameter of the plates (i.e. number of mole- 

 cular layers in du Bois-Eeymond's sense) and the E.M.F. may 

 be assumed as proven, although Schonlein disputes this on the 

 ground of his experiments (30, p. 503). This, moreover, co- 

 incides with the small diameter of the plates of the Torpedo organ 

 9 '6 fji, as compared with those of Gymnotus 8 '2 //,, and Malapte- 

 rurus 4* 8 //,. As stated above, the Torpedo organ, adapted to 

 sea-water, can suffice with less E.M.F., while those of the two 

 fresh-water fishes require much greater E.M.F. to meet their 

 higher internal resistance (greater length, smaller cross-section). 

 Given the surface mass, and under the presumption that the E.M.F. 

 of the plates is proportional to their diameter, du Bois-Reymond 

 (4 e, p. 286) finds the ratio of E.M.F. in the entire organ of 

 G-ymnotus, as compared with that of Torpedo, to be 128 : 1. 



Du Bois-Reymond brought forward the following conclusions 

 as evidence that the molecular hypothesis, in the same form in 

 which it was drawn up for muscle and nerve, accounts for the 

 E.M.F. of the electrical organ also (I.e. p. 288 f.) : "The E.M.F. 

 of a dipolar molecule from a regularly constructed test-muscle, as 

 diminished by short-circuiting, = the double P.D. between equator 

 and poles of the muscle, about 0*15 D. Let it be taken for 

 security sake as = O'lO D. The diameter of the Gymnotus plate, 

 inclusive of the papillae (which are also regarded as electromotive), 

 as compared with the diameter of the Torpedo plate = 8*2 : 9*6 = 

 8*5 : 1 ; the first contains 8 '5 times as many molecules as the 

 second. Two molecules alone, one behind the other, of the Torpedo 

 plate yield a total E.M.F. of 400 X 2 X 0*10 D=* 80 D, which is 

 sufficient. In Gymnotus we reach the formidable value of 

 6000 x 17 X O'lO D = 10,200 D." According to Schonlein 

 (I.e.), the highest E.M.F. that has yet been calculated for the 

 discharge of Torpedo = between 3 and 3 1 D. The calculation 

 was made " either by comparing the deflection from the discharge 

 of the organ with that from a number of Daniell cells, introduced, 

 with the addition of a resistance approximately equal to that of 

 the organ, into the circuit in place of the organ, or by com- 

 pensation " (Schonlein). If with Fritsch we reckon the number 

 of plates in Torpedo ocellata at 370, in T. marmorata at 380 



