ME. Gr. J. ROMANES ON THE LOCOMOTOR SYSTEM OE MEDUSJE. 
675 
water, and found, as I had expected, that the subsequent disturbances of the rhythm 
were precisely similar to those which result from removal of the polypite. 
Now, to draw any inferences from such meagre facts as the above would be hazardous, 
unless we recognize that in so doing our inferences are not trustworthy. But, with this 
recognition, I think there will be no harm in briefly stating the deductions to which the 
facts, such as they are, would seem to point. 
Physiologists are undecided as to the extent in which many apparently automatic actions 
may not really be actions of a reflex nature. Given, for instance, any ganglio-muscular 
tissue which is rhythmically contracting, and how are we to know whether the action 
of the ganglia is truly automatic, or sustained from time to time by stimuli proceeding 
from other parts of the organism \ In most cases experiments cannot be conducted with 
reference to this question, but in the case of the Medusae they may he so ; and it was 
with the view of throwing light on this question that the experiments just described 
were made. Now in these experiments the fact is sufficiently obvious that mutilations 
of any part of the organism modify the rhythm of the marginal ganglia most profoundly. 
That this modification does not proceed from shock, would seem to be indicated 
by the facts that the first effect of the mutilation is to quicken the rhythm, that 
there is a sort of general proportion to be observed between the amount of tissue 
abstracted and the degree of slowing of the rhythm produced, and that the slowing effects 
continue for so long a time. All these facts seem to show that we have here something 
other than mere shock to deal with. A strong suspicion, therefore, arises that the cause 
of the slowing of the rhythm which results from removing the polypite, or a part of the 
general contractile tissue of the hell, consists in the destruction of some influence of an 
afferent character which had previously emanated from the parts of the organism which 
have been removed ; and that the normal rhythm before the operation was partly due 
to a continuous reception, on the part of the ganglia, of this afferent or stimulating 
influence. In support of this view are the facts that the first effect of such an operation 
as we are considering is greatly to accelerate the rhythm, and that this acceleration then 
gradually declines through a period of about a quarter of an hour. These facts tend tc 
support this view’, because, if it is correct, they are what we might anticipate. If the 
polypite, for instance, while in situ, is continually supplying a gentle stimulus to the 
marginal ganglia, when it is suddenly cut off, the nerve-tracts through w'hich this 
stimulating influence had previously been conveyed must be cut through ; and as it is 
w r ell known how irritable nerve-fibres are at their points of section, it is to be expected 
that the irritation caused by cutting these nerve-tracts, and probably also the action of 
the sea-water on their cut extremities, would cause them to stimulate the ganglia more 
powerfully than they did before their mutilation. And here I may state that on several 
occasions, with vigorous specimens, I have observed a sudden removal of the polypite to 
be followed, not merely with a quickening of the rhythm on the part of the bell, but 
with a violent and long-sustained spasm. Again, as regards the other fact before us, it 
is obvious that as soon as the cut extremities of the nerves begin to die dow r n, and so 
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