ie. 
THE ELECTRIC ORGANS OF FISHES. 149 
The essential features of an electric organ as such were 
descyibed in more detail in the case of the Torpedo, and 
the distinguishing characters of the organ in each of these 
representative fish were then alluded to. 
(1) Torpedo. This fish has two electric organs, one 
being situated on each side in the lateral mass of muscles 
external to the gills. Hach organ is composed of a series 
oj hexagonal prismatic columns arranged side by side, the 
base of each column resting on the ventral skin whilst its 
summit is covered by the thicker dorsal skin. The 
number of these columns varies in different species from 
300 to over 1000; but it is constant in any one species, 
and is the same in the young as in the adult stage of the 
fish, the columns growing in size but not increasing in 
number with the growth of the creature. In a very fine 
specimen, measuring 3} feet from head to tail, which was 
shown to the audience and was given to the Zoological 
Museum of University College by the Curator of the 
Public Museum, the number of columns in each organ was 
976; probably the species was the Atlantic 7’. hebetans 
(the T. nobiliana of older writers). Hach column in its 
turn consists of a series of over 500 superimposed plates 
or discs, separated from one another by an albuminous 
liquid, and arranged transversely to the length of the 
column, the whole thus resembling in structure the Voltaic 
pile so familiar to students of electricity. In each organ 
the columns are very richly supplied with separate nerves 
which enter and end in the plates; they are derived from 
four very large nerve trunks, and these emerge from a 
special mass of nerve cells on the dorsal aspect of the 
medulla oblongata, which is known as the electrical lobe. 
By the nervous activity of this electrical lobe the fish is 
able to transmit down the nerves to the plates of the 
columns in the organ, nervous impulses in precisely the 
