148 Miscellaneous. 
dead contractile fibrilla rolled up like a tendril, persisting in this 
state of contraction, and having lost for ever the faculty of elonga- 
tion. 
I have several times observed that as soon as the body of a Vorti- 
cella detaches itself from the stalk to which it normally adheres, the 
contractile stem begins to execute a series of movements of rotation 
round the axis. Each of these movements is accompanied by the 
formation of a spiral turn; and when the whole of the stalk is thus 
converted into a close spiral, the movement ceases, and no elongation 
afterwards takes place. 
The elongation of the spiral fibrilla, the organ of muscular move- 
ment in the Vorticelle, is therefore dependent on the state of life— 
that is to say, on the continuity of nutrition and the exchange of 
materials. From the moment when nutrition is suppressed by the 
death of the animal, or by the separation of the fibrilla from the 
nutritive centre, the contractile element takes and retains the 
natural form inherent in its structure—that of a spiral spring, of 
which the turns are at the maximum of approximation in the state 
of repose. 
The contraction of the muscular fibre of the stalk of the Vorti- 
cella corresponds with the state of repose of the spring; it is the 
immediate consequence of its elasticity ; the elongation of the fibre 
is the result of the forced extension of the spring by a cause of 
movement dependent on the act of nutrition, and acting during the 
apparent repose of the contractile organ. As soon as the source of 
this antagonistic force is exhausted, elasticity, recalling the muscle 
to its natural form, produces the so-called movement of contrac- 
tion. ! 
Is this a phenomenon peculiar to a singular organ of locomotion, 
the stalk of the Vorticella? or is it the condition of muscular con- 
traction in all animals? 
I shall have the honour very shortly to communicate to the Aca- 
demy the results of numerous experiments which I have undertaken 
upon muscular contraction in the higher animals, their results 
establishing :— 
1. That a recent hypothesis, according to which permanent con- 
traction is essentially constituted by a series of successive shocks or 
vibrations, is in absolute contradiction to well-observed facts. 
2. That a tendency towards extreme contraction is a property 
inherent in living muscular fibre, a necessary consequence of its 
structure and elasticity. 
3. That during life this tendency to contraction is combated by 
a cause of extension which predominates during the repose of the 
muscle, is developed in the exchange of nutritive materials, increases 
with the activity of their access, diminishes or becomes extinguished 
by their exhaustion, and may be momentarily suspended by all the 
excitants of muscular contractility—nervous action, heat, the electric 
shock, &c.—Comptes Rendus, June 3, 1867, pp. 1128-1132. 
