MR. G-. J. ROMANES ON THE LOCOMOTOR SYSTEM OF MEDTJSB. 
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that of a number of contractions rapidly succeeding one another — as in the heart under 
similar excitation. This apparent absence of summation will probably require further 
treatment on some future occasion. 
(q) I shall now conclude my remarks on electrical stimulation by describing a highly 
remarkable phenomenon, and one which I am quite unable to explain. I am per- 
suaded, however, that it is a phenomenon well meriting the attention of physiologists. 
When the swimming-bell of Sarsia has had its margin removed, and so, as proved 
by hundreds of similar experiments, has been entirely deprived of its locomotor 
centres, nevertheless in response to electrical stimulation, instead of giving a single 
contraction to make or break, it may begin a highly peculiar motion of a flurried, 
shivering character, which lasts without intermission for periods varying from a few 
seconds to half an hour. I never but once saw a similar motion in the perfect animal, 
and this was in the case of a specimen which was dying from having been poisoned 
with iron-rust. The motion, I think, may be explained by supposing that the various 
parts of the muscle-layer are contracting without coordination ; but why they should 
sometimes do this in response to stimulation, and why, when they do this, they should 
continue the action so long — these questions I cannot answer. In the case of so 
peculiar a phenomenon, however, it is necessary that I should detail all the facts I have 
been able to collect. I have never seen any similar or corresponding action performed 
by the paralyzed bells of other Medusids, and even in the case of Sarsia its occurrence 
is comparatively rare. When it does occur, however, it is always continuous ; that is 
to say, it never spontaneously recommences after having once, ceased. As already 
stated, the period of its duration is extremely variable ; but when this period is long, 
it is observable that the shivering motions become feebler and feebler, until they even- 
tually fade away into quiescence. The animal is then quite dead to all further stimu- 
lation. Beyond saying that the peculiar motions in question never originate independently 
of stimulation, I cannot give much further account of the conditions which determine 
their commencement. The following instances are quoted from my notes in extenso : — 
“ A healthy individual with centres removed, after failing to respond to either make 
or break of direct current, and after about a quarter of a minute’s rest from a series of 
rapidly alternating makes and breaks of this current, began to shiver, and continued to 
do so for five minutes. Aftenvards quite dead.” 
“Another healthy individual, after refusing to contract either on make or break of 
induced current for two or three times, began to shiver and continued to do so for 
twenty minutes. Afterwards quite dead. This individual had been used five minutes 
before for experiments with the direct current, to which it responded well and without 
shivering.” 
“Another healthy individual was left for some time after excision of margin, and then 
put into the well and submitted to induction-shocks. No contraction either on make 
or break with coil pushed to zero. On now trying direct current, without altering 
position of electrodes, violent contraction on make and also a decided one on break. 
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