964 SCIENCE. 
capillary electrometer in consequence of 
the electrical disturbance in the organ 
which is ‘the organ shock.’ A number of 
these records were exhibited ; they showed 
the time relations, mode of commencement 
and manner of subsidence of the shock, and 
demonstrated its similarity to the electrical 
changes known to exist in nervous tissue 
during the passage of a nervous impulse. 
A remarkable feature of the organ shock as 
distinct from the phenomena of nerve was 
then brought forward. The shock even 
when evoked by a single stimulus was 
shown to be rarely if ever a single one. 
Each effect consists of a rhythmical series 
of electrical changes occurring one after 
another in a perfectly regular manner at 
intervals of 74,” to zt,, the rate depend- 
ing upon the temperature. By special ex- 
periments it was shown that this rhythmical 
series is due to self-excitation, each change 
producing an electrical current of sufficient 
intensity to excite the nerves of the tissue 
in which it was generated. It follows that 
only the initial member of the series need 
be evoked by nervous impulses descending 
the nerves, since the others must then en- 
sue. The potency of the organ as a weapon 
to be wielded by the fish is thus enormously 
increased by its resemblance to a self-load- 
ing and self-discharging automatic gun. 
The total electromotive-force of the whole 
organ in a fish only eight inches long can 
reach the surprising maximum of 200 volts, 
at any rate in the case of the initial shock. 
The attainment of this maximum is due to 
the simultaneous development of perfectly 
similar electromotive changes in each of 
the two million discs of which the organ is 
composed. In a single disc the maximal 
electromotive force only amounts to from 
-04 to .05 volt, and since in a small nerve 
an electrical change of .03 to .04 volt has 
been observed, the large total effect is not 
due to any extraordinarily intense electrical 
disturbance in each tissue element, but to 
[N. 8. Von. X. No. 261. 
the tissue elements being so arranged that 
the effect in one augments those simulta- 
neously produced in its neighbors. 
Finally, the remarkable characters of the 
nervous connections of the organ were de- 
scribed. Each lateral half of the organ, 
although it has a million plates receiving 
nerve branches, is innervated by one single 
nerve fiber and this is the offshoot of a 
single giant nerve-cell situated at the ce- 
phalic end of the spinal cord. The struc- 
ture of this nerve-cell was displayed by 
means of microscopic sections and by wax 
models made by G. Mann, of Oxford. As 
regards the nervous impulses which the fish 
can discharge through this nerve-cell, ex- 
perimental results were described which 
show that the fish is incapable of sending a 
second nervous impulse after a preceding 
one until a period of 54, second has elapsed, 
and that this interval is rapidly lengthened 
by fatigue to as much as several seconds. 
The inability of the central nervous system 
to repeat the activity of the organ obviously 
presents disadvantages to the use of the 
shock as a weapon for attack or defence,. 
but such disadvantage is more than count- 
erbalanced by the property of the organ 
alluded to in the earlier part of the lecture,. 
viz., that of self-excitation, since a whole 
series of shocks continue to occur automat- 
ically in rapid succession provided that an 
initial one has been started by the arrival 
of the organ of a nervous impulse sent out. 
from the central nerve-cell. 
Francis Goren. 
SCIENTIFIC BOOKS. 
The Elements of Alternating Currents. By W.S. 
FRANELIN and J. WILLIAMSON. New York, 
The Macmillan Company. 212 pages. 
This book gives an exposition, or rather in- 
troduction into the engineering methods of in- 
vestigation, that is, those methods which are 
used in practice to investigate the phenomena. 
taking place in alternating circuits, and to de- 
sign alternating apparatus. 
