152 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
not cross the South American streams which are infested 
by these creatures, and therefore adopt the expedient of 
driving in their horses upon which the eels fasten and 
exhaust themselves in a vain effort to kill them. When 
exhausted, they are unable through failure of the central 
nerve power, to discharge the organ, and the Indians then 
cross in safety. 
The immunity of the Eel from the effects of electrical 
currents is still more remarkable than that of the Torpedo. 
In each Gymnotus when it discharges its powerful organs, 
the electrical current must pass through its own brain, and 
hence it is not surprising that this fish is very insensitive 
to electrical currents—it feels neither its own discharge 
nor that of any of its neighbours. 
(3) The most remarkable of all the electrical fish, is 
the Malapterurus, which is a comparatively small fish, 6 
to 12 inches long. The electric organ is not situated in 
a mass of muscles as in the Torpedo and Gymnotus, but 
is in the skin of the animal. This skin is thickened and 
forms a thick mantle around the body of the fish, in which 
the same essential disposition of rows of plates can be 
observed. There are, however, an extraordinary number 
of plates, over 4 millions having been estimated to be 
present in one fish. Another remarkable fact, is, that 
the enormous nerve supply of all these plates, is derived 
from two single nerve fibres, which emerge each from a 
single nerve cell situated in the upper part of the spinal 
cord; each of these then has to supply countless branches 
to the 2 million plates in half the mantle. 
The electrical shock and discharge of the Malapterurus 
is extremely intense. | 
(4) In the common skate there is a feeble electrical 
organ which forms a long tapering body situated one on 
each side of the tail; it consists of a few columns contain- 
