520 
experiments of Mittlers Valentin, and others, 
to be erroneous amd unworthy of credit. But 
I have elsewhere* adduced the evidence of 
direet microscopical observations made on living 
ments of the elementary fibre of voluntary 
muscle, entirely isolated from every extraneous 
tissue, whether nerve or vessel, to shew that 
this is a property inherent in this tissue, and 
that, whatever be its source, it is capable of 
being brought into action by a stimulus topi- 
cally applied. Thus, when such a fragment is 
examined, contraction is found to occur first 
at its broken extremities, and if water (which 
has long been known to be a rapid exhauster 
of muscular irritability) be brought into con- 
tact with it, it is seen to absorb the fluid 
and to’be excited to contractions, which com- 
mence at the surface. The same thing is fre- 
gently to be met with under a different form. 
particle of foreign matter, as a hair or piece 
of dust, may be included by design or accident 
in the field so as to touch the side of the fibre 
at a single point. When this happens, the fibre 
will often exhibit a contraction so plain and so 
limited to the point touched, as to give un- 
equivocal proof of its being the result of the 
irritation of pressure. 
Theseinteresting phenomena may be observed 
more or less satisfactorily in all animals whose 
fibres retain their irritability for a sufficient 
length of time after removal from the body, 
and the crab and lobster will be found the most 
favourably adapted for the purpose. In many 
reptiles and fishes, also, the steps occur slowly 
enough to be adequately scrutinized. 
The facts in question can admit only of one 
explanation if it be conceded that the mus- 
cular element has been here separated from 
the nervous; and certainly that separation 
has been effected unless the nervous tubules 
send off from their terminal loops a set of 
fibrils which penetrate the sarcolemma and 
diffuse themselves through the contractile ma- 
terial within; a supposition for which there 
exists at present no foundation in the obser- 
vations of the most diligent investigators of 
this subject. 
They will, therefore, probably, be regarded 
as conclusive proof that contractility is a pro- 
perty inherent in the very structure of muscle, 
and capable of being excited to action inde- 
pendently of the immediate instrumentality of 
nerves. 
The determination of this point must have 
a very important bearing on the question of 
the nature and cause of contraction, into which 
no small confusion has been introduced by 
the attempts to account for that phenomenon 
by various hypotheses of electrical action. That 
one, especially, which aims at establishing an 
attraction between distant points of the fibres 
where the nerye crosses them, (the ‘ zig-zag 
hypothesis’ of Prevost and Dumas,) and which, 
with the wrongly interpreted facts on which it 
principally rests, has had an immense, though 
sometimes unperceived influence, ever since it 
was broached, on the whole question of con- 
traction, is entirely refuted by the facts above- 
* Phil. Trans, 1840, p. 487, 
MUSCULAR MOTION. 
_Thiy important question, like the last, is de- 
mentioned. There are some others, sprung out, 
of this, which do not here require more than a 
passing allusion. ae 
2. Suurce of contractility: whence derived? 
bated up to the present day, but seems 
length to have become disenthralled of 
loose hypotheses which have long in 
with its settlement, The discussion may be 
limited to such particulars as seem to be the 
most conclusive. 
It may be observed that the contractility and — 
development of muscle, other things being t iy 
same, are always proportionate to one another, 
Allcauses interfering with development diminis 
contractility. Thus muscles become atrophied — 
and weak by disuse, by lessening their supply” 
of blood, by cutting off their connexion 
the central part of the nervous system. he 
are, on the contrary, augmented both in size 
and power by active use, during which both 
the vascularand nervous parts supplied to them 
are no doubt urged to increased activity. Tow 
is it to be decided whether these changes Of — 
contractility depend on changes of nutriti¢ 
or whether both be not a common 
changes in the amount of nervous power broug! 
to act upon the muscles. Dr. Marshall Mall 
has remarked that in paralysis from disease 
involving the spinal cord or nerves, asting 
of the muscles is far more rapid and complete 
than in paralysis from affection of the bra 
wherein the spinal cord and its connection Wi 
the muscles remains in a normal state; and 
deduction seems at first sight plain and inevi 
able, that it is from the spinal cord that @ 
contractility is derived, or at least that t 
integrity of the spinal system is essential to 
maintenance of that property in the muscle 
An ingenious experiment of Dr. John Reid’ 
however, proves that this is not the case, 
explains the part which the spinal system play 
in respect of this property in the insta 
referred to. ‘“ The spinal nerves were € 
across, as they lie in the lower part 
spinal canal, in four frozs, and both pos 
extremities were thus insulated from their 
vous connexions with the spinal cord. T 
muscles of one of the paralyzed limbs 
daily exercised by a weak galvanic bai 
while the muscles of the other limb ° 
allowed to remain quiescent. This was 
tinued for two months, and at the end of 
time the muscles of the exercised limb ret 
their original size and firmness and conu 
vigorously, while those of the quiescent 
had shrunk to at least one-half of their’ 
bulk, and presented a marked contrast 
those of the exercised limb. The muse 
the quiescent limb still retained their cor 
tility, even at the end of two months; 
there can be little doubt (adds Dr. I 
from the imperfect nutrition of the 
and the progressing changes in their 
structure, this would in no long time have 
appeared had circumstances itted me 
prolong the experiment.” It is clear from” 
td 
PSU! 
iS 
' 
r 
* Edinb. Monthly Journal of Medical Sei 
May 1841, p. 327. ; 
