MUSCULAR MOTION. 
ing of the material composing the fibre, as is 
shown by the general outline of the part, but 
especially by the appearances visible in its 
interior. The transverse stripes, both light and 
dark, become longer and thinner; in other 
words, the discs expand in circumference, 
flatten and approximate to one another; or to 
use another form of expression, the fibrillz 
become shorter and thicker, both in the par- 
ticles composing them and the material con- 
necting those particles (fig. 301). 
Fig. 301. 
¢ 
tary fibre (from the eel ) partiall: 
Frag t of an elem 
contracted in water, 
@, uncontracted part. 
 b, contracted part, along the border of which, at 
' ¢, ¢, the sarcolemma is raised from the surface 
by the water that has been absorbed, that has 
thereby caused the contraction, and by it has been 
expelled from the contractile mass. 
These changes are always local, or partial, 
and it is most evident from the characters they 
constantly present, that they are not limited to 
any determinate regions, points, or segments, 
but occur indifferently wherever the exciting 
cause may chance to be exerted. Neither discs 
nor fibrille appear to have the smallest share, 
as aggregations of particles bearing those par- 
ticular forms, in producing the phenomena of 
contraction. A contraction is never bounded 
to a particular number of discs or fibrille, and 
is never accurately limited by the interval 
between two discs. It constantly happens that 
at the edge of the contracted part several discs 
are only partially engaged in it. A contraction 
generally, when commencing at the broken 
end of a fibre, occupies its whole width there; 
but when it commences at the border of the 
fibre it may be confined to a portion of many 
discs. And, further, a contraction never occu- 
pies the whole length of a fibre or fibrilla at 
once. A contraction excited in an elementary 
fibre by the contact of a hair extends into the 
Mass equally in all directions, as we might 
Suppose it would do, if the mass were homo- 
geneous. 
In a word, an attentive study of these inte- 
resting phenomena has convinced me that in 
the bare fact of contraction the build of the 
fibre is an item of no importance whatever: the 
exquisite symmetry displayed in the apposition 
of its component particles is, as it were, dis- 
regarded and overlooked, while the whole pro- 
cess is to be referred to the material itself, the 
ultimate tissue, whose property is contractility. 
This property appears to reside both in the par- 
ticles and the substance connecting them. 
The ultimate movements, therefore, on which 
contraction depends, whatever they may con- 
sist in, are molecular, and far beyond the reach 
of sense. 
Magnified 300 diam, . 
523 
It will be perceived that this view of the 
subject is the only one which can harmonize 
the fact of contraction in voluntary muscle 
with the same phenomenon in structures which 
have no complicated internal arrangement of 
particles. In regarding contractility, therefore, 
as a property of the living muscular fibre in 
general, it is meant that it resides in it asa 
property without which it would not be muscle, 
and in such a manner that no particle, how- 
ever microscopic, can be detached from muscle 
which does not of itself, and independently of 
the rest, possess this property, as long as it 
possesses vitality. 
It follows from what has been advanced that 
those hypotheses which refer contraction to a 
force exerted between determinate but distant 
points of the fibre, as where the nervous fibrille 
cross it, or at intervals such as Miiller* has 
sometimes seen in insects, must fall to the 
ground. They are so entirely incompatible 
with the facts above stated that it can scarcely 
be necessary to dwell at length on the other 
reasons for rejecting them, or on the explana- 
tion of the phenomena adduced in their support. 
The main fact on which they have been built 
is that long ago mentioned by Hales, and more 
recently studied with minute care by Prevost 
and Dumas, viz. that in the abdominal muscles 
of the frog detached and excited by galvanism, 
the elementary fibres are seen to be thrown 
more or less into a zig-zag form. It is evident 
that in interpreting what they saw these eminent 
physiologists mistook the relaxed fibres for 
contracted ones. In conducting such experi- 
ments many precautions are required, and at 
the best, nothing of the real process of contrac- 
tion can be witnessed. As Miiller correctly 
remarks, the muscle is too thick to be seen 
under a high power. Besides, the shock of 
galvanism causes only an instantaneous con- 
traction, during which the muscle is so agitated 
that it is in vain to attempt to.examine its con- 
dition. It gets out of the focus of the instru- 
ment. What is seen afterwards is not the 
contraction but its result, viz. an approximation 
of the extremities of the fibres. If the galvanic 
shock has acted uniformly on all the fibres 
(which is rare), they all remain straight; but if 
on a part only, those which have escaped con- 
traction are thrown into zig-zags by having their 
ends brought nearer through their cellular con- 
nexion with neighbouring contracted fibres. It 
is most natural that the precise point of such 
flexures should often be determined by the 
passage of nerves or vessels across the fibres. 
This is corroborated by the circumstance that 
relaxed fibres fall at once into zig-zags when 
their ends are made to approach by mechanical 
means. 
MM. Prevost and Dumas have themselves 
drawn attention to an example of shortening 
without zig-zags in the case of the distended 
abdominal muscles of the female frog before 
spawning. They found that the fibres of those 
muscles when cut across remained straight, 
after shortening from 145 to 107 millimetres. 
* Physiology by Baly, p. 889. 
