216 Papers from the Department of Marine Biology. 
(fig. 24, pl. 6). It should be noted that the brain lies midway between 
the two portions of the electric tissue in which the electromotive force 
is generated, and in a transverse section taken across the body of the 
animal as seen in figure 25, plate 6, we get a better view of this relation 
of the brain to the electric organ. 
» The two poles of the organ, which is possibly some form of multiple 
concentration cell, are + or anode on the upper or dorsal surface of the 
animal and — or kathode on the lower or ventral surface. First 
Cavendish and later DuBois-Reymond worked out the course of the 
current caused by this organ in the surrounding salt water at the time 
of discharge, and the diagram by Cavendish, as well as the later and 
more correct diagram of DuBois-Reymond, are shown in text-figures 1 
and 2, respectively, where the field and its currents at the time of 
discharge are plotted. It can here be seen that the brain is theoreti- 
cally lying in a current of some force running from the anode above 
to the kathode below, outside of the electric organ. These theoretical 
considerations have been proved to be true practically, by experiments 
in the laboratory conducted by the same great investigator, and it can 
thus be stated that the electric motor nerve-cells, in the so-called 
electric lobes of the brain, lie in a current that passes from above 
downward, or in the opposite direction from the current that passes 
through the tissues of the electric organs themselves. 
A word as to the anatomy and general histological arrangement of 
the electric motor lobes of the torpedoes will be useful before proceeding. 
The muscle region which develops into the electric organ of this fish 
is innervated by fibers that proceed from the anterior or motor areas 
of the medulla oblongata. Owing, however, to their immense increase 
in size and the way in which they become massed in two symmetrical 
oval lobes, the two masses are forced by their growth up through the 
median wall of the medulla and come to lie in what appears to be a 
dorsal and sensory position (plate 6, fig. 26). 
All the large cells in this mass, as will be presently described in more 
detail, have several processes, one of which is the neuraxon or efferent 
process. This neuraxon leaves the cell and, joining with other neurites 
from adjacent cells, all pass in these groups toward other similar 
groups, finally uniting to form the very large nerve-trunks that pass out 
of the ventro-lateral edge of the nerve-tract to go to the electric organs. 
Since the neuraxes pass downward on their course they usually leave or 
emerge from the ventral surface of the cell, but thisisnot trueinall cases. 
It is easy to see from this description and from plate 6, figure 26, 
and text-figure 6 that the functional polarity or axis of the cell is in a 
majority of cases dorso-ventral, or, as the fish usually lies, is up and 
down. But while this is true, a not insignificant number of cells are 
so placed that, in order to reach the larger general groups of nerve- 
fibers, their neuraxes must leave them from any of their lateral sur- 
faces or even from their dorsal or upper surface (text-fig. 5). 
