Extensibility is manifested in the animal muscular system under many
circumstances. The different motions of our parts render this property
evident. Such is in fact the arrangement of the muscular system,
that one of its portions cannot contract, without the distension of
another. The thigh being strongly bent, the semi-membranosus, the
semi-tendinosus and the biceps are elongated. The arm being carried
out, the great pectoral is extended, being raised, the great dorsal and
the teres major are stretched. All the great flexions bring into action
this property in the extensors; all the extensions render it evident
in the flexors. A muscle which is stretched by its antagonist is in a
state purely passive; it is as it were for a moment abandoned by its
contractility, or rather it possesses it, without its being brought
into action; it is made to obey the motion that is communicated to
it. Observe that in these cases, the distension is confined to the
fleshy portion, and the tendon has no connexion with it; it remains
the same, whatever may be the distance, of the points of attachment,
for these points are nearer or more remote in the different extensions
to which the muscles are exposed; the longest muscles yield the
easiest. The sartorius, the posterior muscles of the thigh, &c.
exhibit this phenomenon in an evident manner; as their position is
accommodated to it. In general all the muscles remarkable for their
length are superficial, and go most commonly to two articulations,
sometimes even to three or four, as in the limbs. Now the number of
these articulations renders the space comprised between the two points
of attachment susceptible of very great variations, which the great
extensibility of these muscles allows. It may be understood from what
has been said above, that it is to the length of the fleshy fibres and
to the whole length of the muscle, that its degree of extensibility is
to be referred. Those in which many aponeuroses are intermixed, and
which derive in part from these membranes or from tendons their length,
possess less of this property. Hence why, in the same motions, muscles
of the same total length become more or less short, more or less
elongated in their fleshy portion. Observe however that when on the one
hand the tendinous portion predominates much, and on the other that it
is very delicate, it yields a little, as we see in the small plantar
and palmar muscles.
If from the natural state we pass to the morbid, we see the muscular
extensibility manifested in a much more evident degree. In the
face, the air accumulated in the mouth, swells it by elongating the
buccinators; the various tumours of this cavity, as the fungous and
sarcomatous ones, often distend the small facial muscles in a manner
which would astonish us, if we considered the naturally small extent
of these muscles which are trebled and even quadrupled. The muscles of
the eye-lids and the eye in the large carcinomas of that organ, those
of the anterior part of the neck in the great swellings of the thyroid
gland, the great pectoral in large aneurisms or in other tumours of
the axilla, the abdominal muscles in pregnancy, in dropsy, in the
various tumours of the abdomen, &c. the broad and superficial muscles
of the back from wens that are under them, present us these phenomena
of distension in a remarkable manner. The muscles of the extremities
are less subject to them, because on the one hand fewer causes develop
tumours beneath them, and because on the other the aponeuroses do not
yield so easily to these phenomena.
_Contractility of Texture._
The contractility of texture is carried to the highest point in the
muscles. These organs have a continual tendency to contraction,
especially when by being elongated, they have surpassed their natural
size. This tendency is independent of the action of the nerves, and of
the irritable property of the muscular texture. It is influenced by
life, but it is not entirely dependent on it; it depends essentially
on the structure of the muscles. The remarkable phenomenon of the
antagonist muscles results from it. The following is this phenomenon.
Each moveable point of the animal frame is always between two opposite
muscular forces, between those of flexion and extension, of elevation
and depression, of adduction and abduction, of rotation without and
rotation within, &c. This opposition is a condition essential to the
motions; for in order to perform one of them, it is necessary that the
moveable point should be in the opposite motion; in order to bend,
it is necessary that it should be first extended, and reciprocally.
The two opposite positions which a moveable part takes, are for it
alternately the point of departure and the point of arrival; the two
extremes of these positions are the two limits between which it can
move. Now between these limits there is a middle point; it is the point
of rest of the moveable part; when it is found there, the muscles are
in their natural state; when it passes it, some are extended, others
are contracted, and such is their arrangement, that the contraction
and extension which take place in an opposite direction, are exactly
in direct ratio. Hence, in the reciprocal influence that the muscles
exert upon each other, they are alternately active and passive, power
and resistance, organs moved and organs which move. The effect of every
muscle which contracts is not then only to act upon the bone in which
it is inserted, but also upon the opposite muscle. Between two muscles
thus opposed, there is often no solid intermediate organs, as in the
lips, the linea alba, &c. The muscle of one side acts then directly
upon that which corresponds to it, in order to distend it. Now this
action of the muscles upon each other is precisely the phenomenon
of the antagonists; two muscles are such when one cannot contract
without elongating the other and vice versa. Let us examine in this
phenomenon the part of the contractility of texture; it is necessary to
distinguish its influence from that of the vital forces, which has not
been heretofore sufficiently done.
A muscle once placed in the middle position, can only be removed from
it by the influence of the vital forces, by the animal or sensible
organic contractility, because in this position the contractility
of texture of its antagonist is equal to its own, and there is
consequently required a force added to this to overcome that which is
opposed to it. But if the muscle is found in one of the two extreme
positions, for example in adduction, abduction, flexion, extension,
&c. then there will be an inequality of action in the antagonists, as
it respects the contractility of texture; the one most stretched,
will make in order to contract itself, an effort much greater than
that which is already contracted. To maintain the equilibrium, it
is necessary then that the vital forces continue to influence the
contracted muscles. Thus every extreme position of the limbs and of
any moveable part, cannot in an ordinary state be supported except
by the influence of the vital forces. When these forces cease to be
in action, immediately the contractility of texture of the elongated
muscle, which had a tendency to exert itself, but was prevented, exerts
itself, becomes efficacious, and draws back the moveable part to the
middle position, a position in which the equilibrium is restored. Hence
why in all the cases in which the cerebral influence has no power
over the muscles, in which they are not irritated by stimulants, the
limbs are uniformly found in a medium position between extension and
flexion, abduction and adduction, &c. This is the case in sleep, in the
fœtus, &c. I have shewn elsewhere how the osseous arrangement of each
articulation is adapted to this phenomenon, how every kind of relation
between the articular surfaces, except that of this medium position,
exhibits a forced state in which some ligaments are necessarily more
stretched than others, and in which the osseous surfaces are never in
so general contact as in this position. In certain fevers which have
so deleterious an influence upon the muscular life and texture, the
horizontal prostration and extension of the extremities do not arise
from an increase of the action of the extensors, but from the want of
energy of the flexors, which have not power to overcome the weight of
the limb; thus observe that every analogous attitude always coincides
with the signs of general weakness; this is the attitude of putrid
fevers, &c.
The section of a living muscle presents us with two phenomena which are
evidently the product of the contractility of texture.
1st. The two ends retract in opposite directions; there exists between
these divided ends a space proportional to the retraction. This
retraction is not in proportion, as has been thought, to the degrees of
the contractions of the muscle; if it was, it would be sufficient in
a transverse wound, in order to bring the divided edges together, to
place the limb in the greatest possible relaxation; now oftentimes, in
these cases, these ends still remain at a distance; then the retraction
is often superior to the greatest contraction of the muscle considered
in its natural state.
2d. The antagonist of the divided muscle which has no effort to
overcome, contracts and makes the moveable part incline from its side,
if there are not other muscles, which acting in the direction of the
first supply its functions. This last phenomenon takes place also to a
certain extent in paralysis of the face. The mouth is then drawn from
the sound side. I have observed however in this respect, that this
deviation is never as evident as it would be by the division of the
paralytic muscle, which has preserved its contractility of texture.
This remaining contractility forms a partial equilibrium with that of
the muscles of the sound side, during the absence of motions; thus
the deviations do not become very evident until the patients wish
to speak, until consequently the vital forces bring into action the
sound muscles, which the others cannot oppose. The paralysis of the
sterno-mastoideus exhibits for the whole head a phenomenon analogous to
that which the preceding muscles produce for the mouth. Strabismus also
oftentimes arises from this cause.
In general in all the phenomena, it is necessary to distinguish that
which belongs to the vital forces, from that which arises from the
contractility of texture. The muscles are antagonists as it respects
these forces, as well as it respects this contractility; now as the
contraction dependant on the nervous influence or irritability, is
much more conspicuous than that arising from the organic texture, the
phenomena of the antagonists are much more striking in paralysis, when
the sound muscles are brought into action in the first manner. It
appears that in many cases of paralysis, the contractility of texture
of the affected side is also a little altered; but it is never so
completely destroyed, that in the amputation of a paralyzed limb, there
is no muscular retraction. I have made this experiment upon a dog; the
nerves having been cut ten days before, and the limb having remained
immoveable since that period, the division of the muscles produced
a manifest separation between their edges; and even, in afterwards
cutting for the sake of comparison the limb that remained sound, I did
not find any difference.
It is especially when muscles have been first stretched, and this
stretching has ceased, that the contractility of texture becomes
evident. The puncture in ascites and an accouchement as it respects the
abdominal muscles, the opening of deep abscesses as it respects those
of the trunk, the extirpation of a tumour situated under any muscle,
&c. show us this property in action in a very striking manner. There
is however an observation to be made on this point, viz. that if the
extension has been of long continuance, or if it has been frequently
repeated, the subsequent contraction is much less, because the muscular
texture has been weakened by the painful state in which it has been;
hence, 1st, the flaccidity of the abdomen after repeated pregnancy; 2d,
the laxity of the scrotum, after the puncture of an old hydrocele; 3d,
I have seen at Desault's a man who was operated upon in Germany for a
fungus in the mouth, and who had, on that side on which the disease had
been, remarkable wrinkles, owing to the greater extent of the fleshy
part of that side, which could no longer contract like the other;
mastication, at this time could only be performed on the sound side;
4th, when women have had many children, the diaphragm is weakened by
repeated pressure, and hence in part the greater mobility of the ribs,
which compensate in some measure in females for the deficiency of
action of this muscle. I think that in many chronic affections of the
chest and abdomen, in which there is a long continued distension of
this muscle, physicians ought more than they do, to have regard to this
cause of difficulty of respiration, when the principle of distension no
longer exists, as after the evacuation of dropsies, &c.
The extent of the contractility of texture is in the muscles in
proportion to the length of the fibres; hence why in amputations,
the superficial part retracts more than the deep-seated; why in
sleep the phenomena of contractility of texture are very apparent
in the extremities, the muscles of which are very long; why, in the
antagonists, nature has in general opposed muscles of proportional
length; why consequently, a muscle with long fibres has rarely for
a counterpoise one with short ones, and vice versa. The flexors and
extensors of the arm, the fore-arm, the thigh and the leg are nearly
of the same extent; the rotators of the humerus within and without,
the first inserted into the sub-spinal depression, the others into the
sub-scapular, resemble each other also in this respect. The proportion
between the antagonists is still more remarkable on the face, where the
same muscles act most commonly in an opposite direction on each side of
the median line.
The quickness of the contractions, arising from the contractility of
texture, is not like that produced by the animal or sensible organic
contractility, which is uniformly more or less marked, according as
the nervous influence of the stimulant acts more or less strongly.
Every motion originating from the contractility of texture is slow,
uniform and regular; it is only when the muscular texture is weakened
that it diminishes; it does not increase except when this texture is
more developed; hence it follows that the varieties of quickness can
only be observed in different individuals, or in the same individual
at different periods, and not, as in the exercise of the vital forces,
from one instant to another. This is a great and remarkable difference
between the two species of properties.
Death weakens the contractility of texture but does not annihilate
it; a muscle being cut retracts a long time after life has left it.
Putrefaction alone puts a limit to the existence of this property.
It is the same with regard to extensibility. I would observe however
that while the muscles retain the vital heat, they have more power of
retraction, than when the chill of death has seized them.
Haller places on the same line and derives from the same principles,
the phenomena resulting from the contractility of texture, which,
with some slight differences, answers to his dead power, and those
produced by the action of the concentrated acids, alkohol, fire, &c.
on animal substances, which crisp, contract and acquire the horny
hardness from the effect of these different agents. But there are
many differences which essentially separate these phenomena from each
other. 1st. The contractility of texture is very slight in the organs
in which the faculty of having the horny hardness is very evident, for
example, in all the organs of the fibrous, fibro-cartilaginous, serous
systems, &c. &c. 2d. The contractility of texture is distributed in
very various degrees, to the different parts; from the muscles and the
skin, which possess the greatest degree of it, to the cartilages which
seem destitute of it, there are many variations; on the contrary, the
faculty of acquiring the horny hardness from the agents pointed out
is almost uniformly distributed, or at least its differences are much
less evident. 3d. One becomes nothing in dried organs, the other is
evidently preserved for many years, as parchment is a proof. 4th. The
first clearly receives an increase of power from life, especially in
the muscles; the second appears to be hardly modified by it. 5th. This
always exhibits sudden effects, rapid contractions. To feel the contact
of the fire, of the concentrated acids or alkohol, and to assume the
horny hardness, are two phenomena which the second brings together in
the animal parts; the contractility of texture, on the contrary, exerts
itself but slowly, as we have said. 6th. This last can never give
to the parts, the muscles especially, that remarkable density which
they exhibit in their horny hardening. 7th. The absence of extension
of the fibres is the only thing necessary for the contractility of
texture which has an unceasing tendency to activity; it requires on the
contrary in order to crisp the fibres, that they should be in contact
with a foreign body. I could add to these many proofs, in order to
establish an essential difference between the phenomena confounded by
the illustrious physiologist of Switzerland.