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flame, but to detonation (marginal stimulation) with an explosion. In the tissue, 
as in the cotton, every fibre appears to be endowed with the capacity of liberating 
energy in either of two very different ways ; and whenever one part of the mass is made, 
by the appropriate stimulus, to liberate its energy in one of these two ways, all other 
parts of the mass do the same^and this no matter how far through the mass the 
liberating process may have to extend. Now, employing this metaphor, what we have 
to explain is why this capacity of dual response should exist in contractile tissues, and 
why certain slender lines of differentiated tissue should have the capacity, when them- 
selves directly stimulated, of determining the explosive response. And to me it seems 
that neither of these questions is answered by supposing that it is the ganglionic 
element which, when itself directly stimulated, acts as a detonator. That this may be 
the case I do not dispute ; for it is certainly, to say the least, a curious coincidence 
that such a marked differentiation of function as the facts imply should everywhere 
accompany and be restricted to the ganglionic tracts*; but what I desire to insist upon 
is this — that even if the ganglionic element could be proved to be the detonating element, 
the facts before us would not thus be accounted for. Doubtless it would be an 
interesting thing to know that a ganglion-cell may be able to originate two very 
different kinds of impulse, according as it liberates its energy spontaneously or in 
answer to direct stimulation f; but this knowledge would merely serve to transfer the 
questions which now apply to the marginal and polypite tissues in general to the 
ganglionic tissue in particular. Again, the supposition of the ganglia acting as 
detonators when themselves directly stimulated, would in no wise tend to explain why 
it is that the contractile tissues are capable of two such very different kinds of response. 
By detonating ordinary cotton, we can never obtain an explosion ; and, similarly, unless 
the general contractile tissues of these Medusae were in some way prepared to respond 
in a different manner to the different kinds of marginal or ganglionic discharge, we 
should never observe a spasm. 
(/) Another solution of the difficulty may possibly present itself as worthy of consi- 
deration. Bearing in mind the facts already adduced with regard to the high degree 
* As the polypite of Staurophora laciniata is spread out over the radial tubes, it is not improbable that 
ganglionic elements may here occur. 
t It may perhaps be thought that this is too strong a statement. Considering that, in the various species of 
Tiaropsis, spasmodic motions result when any part of the irritable tissues are stimulated, it may appear that 
a spasm differs from an ordinary contraction only in the degree of its intensity ; and therefore that, in 
Staurophora, direct stimulation of the ganglia is followed by a spasm only because a greater amount of 
ordinary ganglionic influence is thus caused to be liberated than would be the case in a merely spontaneous 
discharge. I think, however, that if this were the explanation there ought not to be so immense a contrast as 
there is between the facility with which a spasm may be caused by stimulation of the margin and of the 
contractile tissue respectively. The slightest nip of the margin of Staurophora laciniata, for instance, is suffi- 
cient to cause a spasm, whereas even crushing the contractile tissues with a large pair of dissecting-foreeps 
will probably fail to cause any thing- other than an ordinary contraction. Nevertheless, pricking the margin- 
with a fine needle usually has the effect of causing only a locomotor contraction. 
