164 MEMOIRS OF THE CARNEGIE MUSEUM. 
on this side that each unit receives its nerve-fibers. It is not, however, intended 
here to discuss the microscopic structure. 
Aside from the electric organs the anatomy of the electric eel is very similar 
to that of the other Gymnotids. 
2. Nature and Strength of Electric Shock. 
Sachs states that the electric shock may be received in four ways. 
1. By completing an electric are. 
2. By conduction. 
3. Direct contact. 
4. From the water in which the eel is discharging shocks. 
1. Sachs considers an are to be completed if the electric eel is touched at two 
points. He found the maximum shock was received when the connections were 
made just behind the head and at the end of the tail. This of course included 
the entire mass of electric tissue. Sachs accidentally made such an are with an 
eel three and one-half feet long. Its head fell on one foot and its tail on his other 
leg. The contact lasted for about thirty seconds, during which time Sachs was 
unable to move. He experienced great pain the rest of the day and soreness of the 
limbs for some time afterward. Humboldt tells of stepping on a four foot eel in 
such a way as to make a head and tail connection and being instantly knocked 
down by the shock received. Dr. Eigenmann relates that all of the fishes taken in 
a haul of a large seine were killed by an electric eel, which was among the catch, 
while the seine was being pulled in. The experiments of Sachs showed that the 
strength of the shock varied directly with the amount of the electric tissue included 
in the are. 
2. and 3. Direct contact in but a single place on the fish is also capable of 
transmitting a shock, if the ground completes the circuit. A severe shock can 
be received if the eel is only touched by a finger. In the same way the shock can be 
inflicted through wet wood, cordage, metal, or any other conductor. Glass and 
rubber are insulators against it. 
4. The limit of the effectiveness of the shock in water has never been deter- 
mined. Sachs gives several cases of the transmission of the shock in this way. 
Mules are often knocked from their feet while fording small streams frequented 
by the eels, without actually being struck by them. Natives attempting to get 
out of a boat into the water are frequently unable to get either in or out after 
touching the water if an eel is near by, until the shock ceases. On account of such 
occurrences the natives regard these eels with great fear and hatred, killing them 
when opportunity offers. While experimenting with eels in wooden troughs, 
Sachs found they were able to kill frogs, fishes, and freshwater shrimps (contrary 
to the idea that the last mentioned form is immune) at a distance of several feet. 
A careful count of the number of shocks given by a single eel was made by 
