On the Electric Organ in Malapterurus electricus. 441 



excitation and the organ strip. It is probable that the greater part of 

 this time is occupied by the slow transmission of the excitatory state 

 along the finest sub-divisions of the nerve within the organ near the 

 ultimate nerve endings, all of which were at 5° C. 



(1) The most interesting point in connection with the whole experi- 

 ment is the maximum E.M.F. attained by the response given by the 

 small portion of organ (15 mm.) investigated; this amounted to 25 "10 

 volts in the most favourable instance. 



The contacts were 15 mm. apart, and we convinced ourselves that 

 localised excitatory changes in the piece of tissue situated between 

 these contacts were responsible for the development of the electrometer 

 movements when our apparatus was arranged as indicated in the 

 opening description. This piece of tissue was subsequently removed 

 and appropriately fixed for microscopic examination. Sections were 

 then cut so as to display all the discs lying between the points of the 

 electrode contacts. The recent work of Ballowitz has shown that the 

 nerves do not reach the expanded discs, but end in their caudal stalks. 

 The discs themselves are contained in the lozenge-shaped compartments 

 constituting the columns. These are so situated that one columnar 

 row of compartments is dove-tailed into those of all its neighbours. 

 The result is that the number of discs and stalks in longitudinal series 

 is twice as many as the number of lozenge-shapecl compartments con- 

 stituting any given column. Enumeration of the successive compart- 

 ments in a number of different columns throughout the portion of 

 organ between the contacts (15 mm. long) gave the following figures : 

 260, 265, 262, &c. It was therefore assumed that the electromotive 

 difference of 25*10 volts was probably distributed uniformly over a 

 series of at least 530 discs ; the maximum E.M.F. of the change in 

 any one disc, with its nerve endings, would thus be not more than 

 0*048 volt. It is of intesest to note that in the sciatic nerve of the 

 frog we have obtained an excitatory effect amounting to 0*033 volt. 



(5) The whole organ of the fish measured 12 to 15 cm. The extreme 

 ends are thinned down, but it may be certainly inferred that 12 cm. of 

 this organ would be at least as functionally active as the portion we 

 investigated. This would give a development of 200 volts for the 

 whole series of organ discs, and even this high value cannot be regarded 

 as a maximum for the living fish, since it was evident to us that the 

 organ preparation we employed had its functional activity lowered 

 both by the low temperature and by the operations involved in its 

 dissection. It is worth noting that during the first stages of the dis- 

 section carried out on the entire fish cooled in ice-cold water to 

 anaesthesia, the division of a nerve branch with metal scissors whilst 

 the organ was grasped by metal forceps, caused a strong shock to pass 

 through the arms of the operator (F. G.), which was felt up to the 

 elbows. 



