150 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
same way as it 1s able to transmit such impulses to its 
muscles. In the case of the muscles the arrival of the 
nervous inpulse is followed by a contraction or movement 
in each muscle fibre, whereas in that of the electrical 
organ the arrival is signalised by the production in each 
plate of every column of an electrical effect ; and since in 
the columns a very large number of plates are simultan- 
eously the seat of this electrical change, the total effect 
in the whole organ is to produce an electrical current of 
considerable intensity, which flows through the organ from 
the ventral to the dorsal surface of each column, the 
circuit being completed by the salt-water and surrounding 
tissues. 
The greater the number of columns and piates the 
greater will be the intensity of the electrical effect, provided 
that the nervous impulse which starts it remains at the 
same pitch of intensity. If only one group of nervous 
impulses travel from the brain to the organ, a single 
electrical effect in the columns of very short duration (only 
2,- second) is produced, and the effect of this upon such 
an object as a man’s hand placed upon the fish is precisely 
like that produced by one electrical shock. It is there- 
fore termed the ‘“‘ shock”’ of the organ. 
The fish has however the power of discharging a second 
and third group of nervous impulses, and may discharge 
several hundreds of such groups, following one another at 
the rate of one hundred per second. The physiological 
effect of this is very considerable, numbing the hand placed 
on the fish: it resembles that caused by the successive series 
of electrical shocks discharged from a magneto-electric 
machine. Such a succession of shocks is the normal 
response of the animal to irritation, and is called a “ dis- 
charge.”” As the power to send these rapidly following 
shocks is dependent upon the functional activity of the 
