Chapter XI: Part 11

The direction of the fibres of the periosteum is nearly analogous to that of the bones, the long bones especially as well as the short; but it has not the radiated structure of the flat bones that it covers. These fibres placed upon each other, have different lengths; the superficial ones are the longest; those which correspond immediately with the bone run but a short distance. In general all become very evident in some diseases of the bones. I recollect among other examples of the preternatural development of the fibres, a man affected with elephantiasis, and at the same time a swelling of the compact texture of the tibia, which was of a remarkable thickness. The periosteum of this bone was very thick, and adhered so little to the bone, that the slightest effort was sufficient to raise it in its whole extent, and its fibres were so distinct, that it might have been taken, when separated from the bone, for a portion of plantar or palmar aponeurosis.

The periosteum borrows its vessels from those of the neighbouring parts. Their innumerable branches ramify in it ad infinitum, form there a net-work, which injections, especially in infants, make very evident, they are afterwards lost in it, or penetrate the compact texture of the bone, or return to the neighbouring parts to form anastomoses.

This membrane receives, as we have said, the insertion of almost all the fibrous system, of the tendons, the ligaments and especially the aponeuroses. This insertion has no connexion with the bone in infancy; but ossification soon seizing upon the most internal laminæ, all the fibrous organs appear to be identified with the bone in the adult. I would observe that this arrangement coincides with the prodigious power of drawing that the muscles, having become more developed, often exert at this age, and which only spent upon the periosteum, as it would have been without its ossification, would not have found in it a sufficient resistance, whereas acting also upon the bone, it moves it without endangering its covering. The general organization, the properties and the life of the periosteum are the same as those of the fibrous system; I shall not treat of them.

_Development of the Periosteum._

In the fœtus, this membrane is soft, spongy, containing much gelatinous fluid; it melts easily in water; its fibres are not distinct; they become so as we advance in age, and at the same time the softness diminishes and the resistance increases. The periosteum in old age has extreme tenacity; it resists ebullition almost as much as the ligaments; those who prepare skeletons know this very well. It tears in various places, because its fibres in contracting are detached from the bone; but what remains becomes with great difficulty gelatinous.

_Functions of the Periosteum._

The periosteum defends the bones which it covers from the impression of the moveable parts that surround it, from that of the muscles, of the arteries, whose pulsation would wear them, as happens in certain aneurismal tumours near the sternum, the vertebræ, &c.

It is a kind of parenchyma of nutrition in reserve, if I may so express myself, always ready to receive the phosphate of lime, when it cannot be carried upon the bone that has become diseased; hence natural and artificial necroses which never take place in the teeth, from the want of this membrane. These little bones have caries and various alterations, but not true necrosis.

We cannot doubt that the internal laminæ of the periosteum are successively ossified, and thus contribute not a little to increase the bone in thickness, when its increase in length is finished. I would observe upon this subject, that not only it, but all the fibrous system, has a singular affinity with the phosphate of lime. Next to the cartilaginous system, it has the greatest tendency to be encrusted with it, no doubt because its kind of general vitality, of organic sensibility in particular, has much analogy with that of the bones. Where the tendons in sliding upon the bones experience great friction they become osseous. The dura-mater and the tunica albuginea are very often ossified; the sclerotica serves as a parenchyma for much earthy substance in birds, which in consequence have it extremely hard.

The periosteum has no connexion with the formation of the bones; it is only accessory to that of the callus; it is a kind of limit which circumscribes within its natural bounds the progress of ossification, and keeps it from irregular aberrations. Does it prepare the blood which serves to nourish the bones? This question cannot be settled by any experiment; but we are sure that the vital properties which it enjoys, do not enable it to accelerate the circulation of the blood arriving at the bones, as some authors have thought.

It seems to me moreover that they have described the periosteum too exclusively in relation to the bones; no doubt it is necessary to these organs; but perhaps it performs in relation to the fibrous organs a still more important part. If nature has placed it everywhere on the osseous system, it is probably in great part, as I have said, because it finds in this system a general, solid and resisting support, which enables it to resist the various drawings, that the whole fibrous system makes upon it, drawings which are sometimes communicated to this last system. This is a new point of view in which the periosteum should be described, and it will yield much more to general considerations, than that in which Duhamel, Fougeroux, &c. have considered this membrane.

IV. _Perichondrium._

We find on all the non-articular cartilages a membrane exactly analogous to the periosteum, and which is called perichondrium. The larynx, the ribs, &c. exhibit it in a very evident manner; it is delicate, with fibres interlaced in all directions, less closely united to the organs it covers, than the periosteum is to the bones, because the cartilages having on their surface less numerous foramina, it does not send to them as many fibrous elongations; hence a less intimate relation between the life of the perichondrium and that of the cartilage, than between that of the bone and its periosteum.

I have twice in a young dog removed from the thyroid its external membrane, and closed the wound immediately, which has been cured without apparent alteration in the organization of the cartilage; at least it has continued to perform its functions. The same experiment might easily be made on the cartilages of the ribs; I have not attempted it. The perichondrium has appeared to me in many injections to contain fewer blood vessels than the periosteum; its uses are analogous to those of this last membrane.

ARTICLE SIXTH.

OF THE FIBROUS CAPSULES.

The fibrous capsules are infinitely more rare in the economy, than they have heretofore been thought to be. The scapulo-humeral and the ilio-femoral articulations are almost the only ones furnished with them. Elsewhere there is nothing scarcely but synovial membranes.

I. _Forms of the Fibrous Capsules._

These capsules form a kind of cylindrical sac open at the two extremities, attached by the circumference of its openings, around the superior and inferior articular surfaces, intermixing at its insertion with the periosteum. They are so much the more loose, as the motions of the articulations are the more extended; that of the humerus, for example, allows a much greater separation of the osseous articular surfaces, than that of the femur; their length in fact is almost the same. Now, as on the one hand, the neck of the first bone is much less than that of the second, and as on the other, both these capsules are inserted at the base of this neck, it follows that the extent of the separation is in the inverse ratio of the length of the articular necks.

Much cellular texture surrounds these capsules externally, which the tendinous fibres and even the tendons coming from the neighbouring muscles, strengthen remarkably. They are sometimes open to allow tendons to pass which are inserted in the bone between them and the synovial membrane, an example of this is seen in the scapulo-humeral articulation for the sub-scapularis. Anatomists who have observed the insertion of the tendons in the capsules, have concluded from it, that the muscles of these tendons were destined to prevent the capsule from being pinched by the articular surfaces in motion. This appears to me improbable; but at least the muscles are destined to prevent the looseness of the capsule during the great motions, which would have been weakened by this looseness; thus there are many of this kind of muscles at the humeral capsule, whilst we see none of them at the femoral, which is, as I have said, much less loose. Within, the capsules are very closely united to the synovial membrane, especially in adults; for in infants, this adhesion is less. Near their extremity however this relation does not exist, because the synovial membrane being reflected upon the cartilage, a triangular space is left between it and the capsule which is attached to the bone, and as this arrangement continues all round the articulation, there results from it a kind of circular canal, filled with cellular texture, and covered with vessels, which I have sometimes distended with an injection pushed into a small opening made for the purpose.

The intimate union of the capsule with the synovial membrane prevents its folds and also its contusion in the great articular motions.

II. _Functions of the Fibrous Capsules._

Why are the fibrous capsules found only around the first kind of articulations? The reason of it is plain; as these articulations have in all directions motions nearly equal, they should have on all sides an equal resistance, whilst the others moving in one or two directions only, the ligaments were unnecessary except at certain places, to limit these motions. Hence why for example, the fibrous system is spread out like a membrane around the ilio-femoral articulation, and collected into distinct fasciæ around the femoro-tibial, where the synovial membrane is almost everywhere bare.

We understand from all that has been said, that the only use of the fibrous capsules is to strengthen the articular relations, and that this use has no connexion with synovial exhalation.

When in luxations not reduced, the head of the bone has left the articular cavity, a new membrane is formed around it in the cellular texture which serves for a capsule; but this membrane has not the texture of the former one. I have observed in two subjects, that no fibre could be distinguished in it, that its texture was very analogous to that of the different cysts that are often found in many parts of the economy, of those especially that form round foreign bodies, the presence of which is not a cause of suppuration, and that consequently these preternatural capsules belong rather to the class of serous than to that of the fibrous membranes.

ARTICLE SEVENTH.

OF THE FIBROUS SHEATHS.

The fibrous sheaths are, as we have said, partial or general.

I. _Partial Fibrous Sheaths._

The partial sheaths destined to a single tendon are of two sorts; one runs a long course; such are those of the flexors of the foot and the hand, which correspond to the whole concave surface of the phalanges; the others form only a kind of rings, in which a tendon is reflected, an example of which is seen in the great oblique muscle of the eye.

All in general form a semi-circle and make half of a canal which the bone completes; so that the tendon slides in a canal half osseous and half fibrous. This canal is lined by a synovial membrane, the attachment of which to the fibrous sheath is equal to that of the articular synovial membrane to its capsule. By their external surface, the fibrous sheaths correspond with the neighbouring organs, to which they are united by a loose cellular texture.

All these sheaths are of a very dense and compact texture; they are stronger in proportion to the effort which the tendons can exert upon them, than the fibrous capsules are in relation to the different impulses which the bones can communicate to them and which tend to rupture these capsules. They are confounded with the periosteum at their two edges. Those of the flexors unite also by their extremity with the expansion of the tendons; hence the very considerable fibrous interlacing that is observed at the extremity of the last phalanges.

In the limbs, the flexors only have these sheaths; the extensors are destitute of them. This arises first from this, that there are two tendons of the first kind to each finger, whilst there is only one of the second, and that consequently more force is necessary to retain them in the first direction. In the second place, each extensor tendon receives on its sides the insertion of the small tendons of the interosseous muscles and the lumbricales, which by drawing it in an opposite direction in the great motions, retain it in its place, and thus compensate for the fibrous sheaths that are wanting. Finally the efforts of the extensors are much less than those of the flexors, of which they are as it were but a kind of moderators.

II. _General Fibrous Sheaths._

The general sheaths are seen especially at the wrist and the instep, where they have the name of annular ligaments. They are destined to confine many tendons together. As in these two places, all those of the hand and the foot pass in a very narrow space, it is necessary that they should be strongly supported. Besides, these sheaths serve also sometimes to change their direction, as we see in those that go to the thumb, whether to its palmar or its dorsal face, and which evidently make an angle at the place of their passage under the sheath. The tendons of the little finger have also an analogous arrangement.

These sheaths exhibit also two great modifications; in the one, as on the anterior part of the wrist, all the tendons are found contiguous, separated only by a kind of loose membrane which is placed between them; in the others, as on the posterior part of the wrist, under the general sheath, are found small fibrous partitions, which separate the tendons from each other. In general, the resistance of these sheaths is very considerable.

ARTICLE EIGHTH.

OF THE APONEUROSES.

We have distinguished aponeuroses as being of two classes, those for covering and those for insertion.

I. _Of the Aponeuroses for Covering._

The aponeuroses for covering are general or partial.

_Aponeuroses for General Covering._

They are found around the limbs, whose muscles they tie down. The arm, the fore-arm and the hand, the thigh, the leg and the foot, are provided with them.

_Forms._

They are, in their conformation, analogous to the form of the limb, which they in part determine, and which they especially maintain, by preventing the displacement of the subjacent parts, a displacement which would continually take place, from the laxity of the cutaneous organ. Their thickness varies. In general, the greater the number of the muscles they cover, the greater their thickness; hence why the aponeurosis of the fascia lata is superior in this respect to the brachial; why that of the fore-arm is thicker in front than behind; why the plantar and palmar are so considerable, whilst hardly any fibres are found on the back part of the foot and the hand. There are however some exceptions to this rule; for example, the aponeurotic covering of the posterior part of the leg is not in proportion to the power of the gastrocnemii and solæus muscles; thus these muscles are more than all the others exposed to displacements, frequently very painful, which constitute cramp, and which it is necessary to distinguish from the pains or numbness which result from the compression of one of the nerves of the lower limbs, as of the sciatic, or the external plantar, a compression produced by a bad position, or any other analogous cause.

Externally, the aponeuroses of the general covering are contiguous to the integuments. A very loose texture unites them, so that the latter can easily slide over them in external pressures. Immoveable between these motions and those of the muscles, they entirely separate them; so that the skin and the muscles that correspond to it, have not, in this respect, any influence upon each other.

Within, these aponeuroses are in general loosely joined to the muscles by cellular texture. Here and there they send between the different muscular layers numerous elongations, which are afterwards attached to the bone, and which, at the same time that they furnish points of attachment, increase the solidity of the covering of the limb.

_Tensor Muscles._

The aponeuroses for general covering have almost all one or two particular muscles that are inserted in them in whole or in part, and which are destined to give them a degree of tension or relaxation proportioned to the state of the limb. This arrangement is remarkable in the insertion, 1st, of the great dorsal and pectoral muscles in the brachial aponeurosis; 2d, of the biceps in that of the fore-arm; 3d, of the palmaris longus in the palmar; 4th, of the glutæus maximus and of the fascia lata in the aponeuroses of that name; 5th, of the semi-tendinosus, semi-membranosus and biceps in the tibial.

As in the great motions of the limbs, in which all the muscles are the most liable to be displaced, these are necessarily in action, they distend powerfully the aponeurosis, which thus reflects the motion that is communicated to it, and resists especially every displacement. When the limb is at rest, the tensor muscles cease their contraction, and the aponeurosis is relaxed. I would observe, that the muscles attached to the fibrous capsules, as to that of the humerus, for example, perform for them the same functions, that the tensor muscles do for their respective aponeuroses.

The colour of these last is a brilliant white; in this respect they differ from all the fibrous organs thus far examined, and are analogous to the tendons, from which they differ a little however in their nature; in fact, they yield less quickly to maceration and ebullition; their fibres are more stiff and resisting. There are no aponeuroses exactly like the tendons, except those which are essentially formed by their expansion or which are at their origin, as those spread upon the anterior rectus of the thigh, those which are concealed in the fleshy fibres of a muscle, and afterwards go out of it to become a tendon. In certain parts of the limbs, as at the top of the arm, for example, the aponeuroses of general covering are insensibly lost in the cellular texture, without our being able to draw the line of demarcation. This arrangement is almost peculiar to the fibrous system; at least I know of no one which thus intermixes and loses its fibres in the cellular texture; it is so much the more remarkable, as the nature of the two textures is essentially different; they do not yield the same products, and they have not the same organic arrangement.

The fibres of the general aponeuroses are only interlaced in two or three directions; this interlacing is almost always very evident to the naked eye. But I have observed that by plunging an aponeurosis into boiling water, and leaving it there for some time, its fibres, in the horny hardening they then undergo, become still much more evident. This observation is moreover applicable to the whole fibrous system, to its organs especially, whose texture but little apparent seems at first view to be homogeneous. In this way, we distinguish very well the fibres of the dura-mater.

_Functions._

The constant compression made upon the limbs by their aponeuroses, besides the uses pointed out, has that of favouring the circulation of the red and white fluids. Thus varices, which are very rare in the deep veins which accompany the arteries, are extremely common in the superficial ones placed beyond the influence of this compression, which art imitates by the application of tight bandages, the effect of which is so advantageous in many external diseases arising from the want of tone, and the relaxation of the parts. I have uniformly observed that the serous infiltrations always begin in the sub-cutaneous cellular texture, that it is only in an advanced stage of dropsy, that we find effusion in that which is under the aponeuroses, and that in general it does not contain as much serum in proportion as the other. In most of the great distensions of dropsical limbs, when the skin is removed and the subjacent water has flown off, the limb covered by its aponeurosis, is scarcely larger than in the ordinary state. The muscles not protected by these coverings, like those situated on the sides of the abdomen for example, become dropsical much more easily.

_Aponeuroses for Partial Covering._

These aponeuroses are met with in insulated parts, in front of the abdomen, on the head, the back, &c.; they are usually destined to retain in place a certain number of muscles which they do not surround on all sides, like the preceding, but with which they correspond only in one direction. Their thickness is much less than that of the preceding ones; it is adapted to the efforts that they are to support.

All have a tensor muscle which proportions their degree of relaxation or of tension to the effort of the neighbouring muscles. The anterior rectus, by means of its intersections, and the pyramidalis, perform this office for the abdominal aponeuroses; the small posterior dorsocostals do it for that which covers the muscles of the vertebral foramina; the auricular, the frontal and the occipital for that of the cranium.

The aponeuroses of covering, whose use is limited to one muscle only, like that, for example, of the temporal, want the tensor muscle, and have consequently the same degree of tension always; it is on this account no doubt that they have a very compact and thick texture, as that which I have just mentioned is an example.

In general, the use of all the aponeuroses of covering whether general or partial, relative to the compression of muscles, is required by the displacements of which they would be susceptible in contracting, displacements evident, 1st, when we place the hand upon a muscle in action, and which is destitute of aponeurosis, as the masseter; 2d, when a wound having injured a considerable part of an aponeurosis of covering, the subjacent muscles become accidentally contiguous to the integuments; 3d, when in an animal we lay bare the muscles of a limb, and leave only the cellular texture to confine them, and in this state excite their contraction; 4th, in certain wounds of the muscles happening at the instant of their contraction, it is difficult to probe these wounds, because in their relaxation the muscles taking a different position, the relations change between the parts that formed the two edges of the wound.

_Of the Aponeuroses of Insertion._

We have divided into three species the aponeuroses of insertion.

_Aponeuroses of Insertion with a Broad Surface._

They are very numerous. Sometimes they arise from the expansion of a tendon, as we see in those of the anterior rectus of the thigh; sometimes, as in the masseter, they derive their origin immediately from the bones. Sometimes it is on one side only that the insertion is made; at others it is on both at the same time, and then they appear like partitions placed between the fleshy fasciæ, which they serve at the same time to separate and unite, as we observe in the muscles that arise from each of the condyles of the humerus.

These aponeuroses always receive in a very oblique direction the insertion of the fleshy fibres. Their mutual adhesion is intimate; I shall speak of it in treating of the tendons.

They have the great advantage of multiplying prodigiously the points of insertion, without requiring great osseous surfaces. The width of the whole of the temporal fossa would not be sufficient for the masseter, if it was inserted by separate fibres. By means of the aponeurotic partitions which receive its fibres and are afterwards fixed in the bone, its insertion is concentrated upon one of the edges of the zygomatic arch. Thus in general, all the very strong muscles, whose fibres are consequently very numerous, are crossed by similar aponeuroses, as the deltoid, the pterygoids, &c. are a proof.

Almost all these aponeuroses are exactly like the tendons; many are continuous with them and then their fibres remain in the same direction. In general, it is a character of these aponeuroses not to have their fibres crossed in different directions, like those of the aponeuroses of covering; the reason of it is plain; the fleshy fibres to which they give attachment being all nearly in one direction, or at least not crossing, it is necessary that these should be like them as they are continuous with them.

I have made an experiment which shows very evidently the identity of the tendons with these aponeuroses; it consists in macerating for some days a tendon; it then becomes supple; its fibres separate; by stretching in the direction of its width, it forms a kind of membrane which it would be impossible to distinguish from a true aponeurosis.

_Aponeuroses of Insertion in the form of an Arch._

They are much more rare than the preceding. When a great vessel passes under a muscle, nature employs this means, so as not to interrupt the insertion of the fleshy fibres. The diaphragm for the aorta, the solæus for the tibial artery, exhibit an arrangement of this kind. The insertion is made on the convexity, and the passage of the vessel under the concavity of the arch, both extremities of which are fixed in the bone. It has been thought for a long time that the arteries could be compressed under these arches; and hence the explanation of popliteal aneurisms, of apoplexy by the reflux towards the head of the blood interrupted in the aorta, &c. But it is very evident that by contracting, the fleshy fibres would enlarge the passage, instead of contracting it, since the necessary effect of these contractions is to enlarge in all directions the aponeurotic curve, an effect which would be directly opposite, if their insertion was made at the concavity. These aponeuroses are strongly interlaced and very resisting.

_Aponeuroses of Insertion with Separate Fibres._

They are a collection of an infinite number of small fibrous bodies wholly distinct from each other, which seem to be detached from the periosteum, as the threads of velvet go off from their common woof. Each is continuous with a fleshy fibre; so that when by maceration we remove all those fibres, these small bodies become floating and are seen perfectly well, especially when the periosteum which has been detached is plunged into water.

It is evident that this mode of insertion on the part of the muscles requires always broad osseous surfaces, since each fibre has a place of its own; we have an example of it in the superior part of the iliacus, of the anterior tibialis, of the temporal, &c. If all the muscles were inserted in this manner, ten times more surface in the skeleton would not be sufficient to receive them.

ARTICLE NINTH.

OF THE TENDONS.

The tendons are a kind of fibrous cords, intermediate to the muscles and the bones, transmitting to the second the motion of the first, and performing in this function a part wholly passive.

I. _Form of the Tendons._

Usually situated at the extremities of the fleshy fascia, they sometimes however occupy the middle, as we see in the digastric muscle; they are almost always found at the most moveable extremity, that which serves for support having aponeuroses for insertion, as we see especially on the fore-arm and the leg, of which all the muscles inserted above by broad osseous or aponeurotic surfaces, terminate below by a more or less slender tendon. From this arrangement result, 1st, little thickness at the extremity of the limbs, and consequently facility in their motions; 2d, great resistance to external pressures very frequent in this place, the fibrous texture being, as we have said, very resisting; 3d, the concentration of the whole effort of a muscle oftentimes very thick upon a very narrow osseous surface, and for the same reason the extent and force of the motions of the bone.

The tendinous forms are usually round, no doubt because they are those in which, with the least size the greatest quantity of matter enters. Sometimes however as in the tendons of the extensors of the leg and the fore-arm, they are flat.

Sometimes bifurcated or divided into many secondary elongations, the tendons are inserted into the bones, or receive fleshy fibres in two or many different points. All are covered by a loose texture which allows them to slide easily upon each other, or upon the neighbouring parts. Sometimes this texture is wanting, and then the synovial capsules surround them to favour their motions. Their extremity, in which the fleshy fibres are fixed, receives these fibres differently. Sometimes it is to one side only that they are attached; hence the semi-penniform muscles; at other times it is to both sides at the same time; this constitutes the penniform. Frequently the tendon is buried so deep in them, that it cannot be laid bare, but by dividing them longitudinally.

The adhesion is very great between the fleshy and tendinous fibre. Yet by macerating them a long time or subjecting them to ebullition, they gradually separate from each other. I have observed that in young subjects the union was much less intimate; thus by scraping at this age the tendon with a scalpel, we remove from it the muscle, without its ever appearing again; the polish is almost the same where the fibres are inserted, as where they are naturally wanting. The extremity of the tendon fixed to the bone, intermixes with the periosteum as it usually expands; so that it is with this membrane, and not with the bone itself, that the tendon makes part, because in fact it is the membrane which is of the same nature; thus if it finds an analogous membrane, it fixes to it equally, as we see in the insertion of the straight and oblique muscles in the sclerotica, of the ischio and bulbo-cavernous ones in the membrane of the corpus cavernosum. In general the tendons never unite but to fibrous membranes; the serous, the mucous, every organ in a word, foreign to the fibrous system, is also heterogeneous to them.

II. _Organization of the Tendons._

The fibrous texture is extremely compact in the tendons; many appear homogeneous at first view; but by examining them with care, we soon distinguish fibres, connected by a small quantity of compact cellular texture. Ebullition renders these fibres very evident; when we plunge suddenly the tendon into boiling water at the place where it has been cut transversely, they become a little thicker at this divided extremity, swell as it were and are thus very evident. At the place where they expand to form an aponeurosis or to unite to the periosteum, these fibres can be distinctly seen without any preparation. On the other hand, as we can always, as I have said, reduce artificially a macerated tendon to an aponeurosis, and as in this state of maceration, soft and loose, it yields to all the forms we wish to give it, it is an excellent means of distinguishing the tendinous fibres. In this experiment so easily repeated, I have never seen the spiral form of the tendinous cylinders, of which some modern authors have spoken. These fibres are in the tendon as at the place where they separate to form an aponeurosis, that is to say in a right line.

Blood scarcely enters the vascular system of the tendons; but in some inflammations, they are wholly penetrated by it. I have seen one of those of the extensors, laid bare in a whitlow, so red, that it had the appearance of a phlegmon. Yet I observed that this colour was not, as in many other inflamed organs, dependant on the small red striæ, an indication that the exhalants are filled with blood; but it was uniform, as for example a body dyed red. In general, it appears that of the whole fibrous system, it is the tendons which have the least energetic degree of vitality, and the most obscure vital forces. By dissecting them in a living animal I have found that they have exactly the same arrangement as in the dead body; the white fluids that penetrate them do not flow under the scalpel; they are dry and can be removed by layers. They appear to have a very low temperature; for, in general, the degree of heat of an organ is in proportion to the quantity of blood vessels it receives.

If in the body they are at the general temperature, it is only because the neighbouring organs communicate theirs to them. Caloric is not disengaged in their texture.

The tendons have a remarkable affinity to gelatine and even the phosphate of lime; where they slide upon a bone, and where they suffer a great friction, they exhibit a hardness which authors attribute to pressure, by comparing it to the callous hardening of the sole of the feet, but which is owing evidently to an exhalation in the tendinous texture of the two preceding substances, an exhalation which the motion produces and from which arises a real ossification.

It is thus as we have said, that the different sesamoid bones are formed, and the patella in particular, a bone the texture of which evidently differs from that of the others, because in the midst of the gelatine and of the phosphate of lime that penetrate it, there remains in it a part of fibrous texture which is not seized upon by these substances, and which is so considerable that its kind of vitality and organization belong as much and more to that of the fibrous system, than to that of the osseous.

Besides, if we detach the patella or any sesamoid bone, leaving with it a tendinous portion of each side, and expose them to the action of an acid, this calcareous substance is removed, the fibres of the bone are exposed, and we see that they are a continuation of those of the tendon which is then softened.

The muscles of organic life, and most of those which in animal life form the sphincters, are destitute of tendons. This white texture, those silver cords that are found in the heart, have not the nature of the tendons of the limbs.

ARTICLE TENTH.

OF THE LIGAMENTS.

We have divided the ligaments into those with regular fasciæ, and into those with irregular ones.

I. _Ligaments with Regular Fasciæ._

They are met with in general in almost all the moveable articulations, and especially upon their sides; hence the name of lateral ligaments by which most of them are designated. Some however are foreign to the articulations, as we see an example in that extending from the coracoid to the acromion process, in those which complete the different osseous fissures, the orbitary for example.

These organs form fasciæ sometimes round, sometimes flat, fixed to, or rather intermixed with the periosteum by their two extremities, easily removed with it in childhood, holding to the bone in the adult by the ossification of the internal layers of this membrane.

Their analogy with the tendons is very striking; the external difference is that they hold to the periosteum at both sides, whilst on one side the tendons are contiguous with the muscles. We see sometimes that the same organ is a tendon at one age, and a ligament at another. This arrangement is remarkable in the inferior ligament of the patella. Yet there are, as we have remarked, differences of composition between them. All result from an assemblage of fibres parallel in the middle, diverging at the extremities, united by a cellular texture more loose than that of the tendons, and which often contains some fatty flakes. This substance is sometimes so abundant in them, that they have an appearance analogous to that of the fatty muscles; I have made this observation on the ligaments of the knee, in a subject elsewhere very thin.

There are some blood vessels in the ligaments. In certain diseases of the articulations, their vascular system is developed in a very remarkable manner, and they are penetrated by a great quantity of blood; no nerve is discoverable in them.

Sometimes the ligamentary texture is changed into a matter like lard, in which every kind of fibre disappears, which rarely returns to its primitive state, and which is met with almost always in organic affections, fatal to the patient.

The ligaments unite strongly the osseous surfaces, prevent their displacement, and yet allow easy motions; a double function which they perform in virtue of a double property, of their resistance on the one part, of their softness and flexibility on the other; sometimes externally, they serve for some muscular insertions.

II. _Of Ligaments with Irregular Fasciæ._

These are irregular fibres scattered here and there upon the osseous surfaces, without any order, intermixed in different directions between the sacrum and the ilium, upon the summit of the acromion, &c. We see many of these fibres, around some of the moveable articulations; much cellular texture separates them. They cannot offer any general views.

In general, the fibrous system is not as regularly organized in the ligaments as it is in the tendons, as the muscular system is in the muscles, &c. In the ligaments even with regular fasciæ, we often see fibres going in different directions, separating from the principal fascia, without any very distinct order.

FIBRO-CARTILAGINOUS SYSTEM.

The fibro-cartilaginous system is composed of different organs which anatomists have sometimes placed among the cartilages, and sometimes among the ligaments, because they in fact partake of the nature of both. I make a system of them between the two preceding ones, a knowledge of which will facilitate the understanding of this.

ARTICLE FIRST.

OF THE FORMS OF THE FIBRO-CARTILAGINOUS SYSTEM.

We may divide the fibro-cartilaginous organs into three classes.

The first comprehends those which are found in the ears, the alæ of the nose, the trachea, the eye-lids, &c. They are very delicate, like membranes, sometimes arranged in an uniform manner, sometimes bent in various directions. As neither their position nor functions have any thing in common, we cannot give them a denomination derived from their forms. We may designate these substances by the name of membranous fibro-cartilages. Besides it is not only in its form, but also in its nature, that this class differs from the others, as we shall see.

In the second class are ranked the inter-articular substances, which occupy the interstices of the moveable articulations, whether they are in part loose in the cavity, like those of the knee, of the lower jaw, &c. and go in different directions according to the motions, or whether, like that of the body of the vertebræ, they are fixed in a solid, though moveable manner, on the osseous surfaces. These organs are in general thicker than the preceding, very various in their form, representing commonly a kind of laminæ, sometimes perforated through the middle in the articular cavities, arranged in very thick fasciæ, and formed like the body of the vertebræ in the vertebral column. We may designate them under the name of articular fibro-cartilages.

I refer to the third class certain portions of the periosteum in which the nature of this membrane is entirely changed, becomes penetrated with gelatine and exhibits an aspect at first analogous to that of the cartilages, but in which it is easy however to distinguish the fibrous texture. These portions are found in the tendinous sheaths, in which they facilitate the sliding of the tendons, and defend the bones from their impression. They may be called the fibro-cartilages of the tendinous sheaths.

These three classes of fibro-cartilages, though very analogous, have not exactly the same structure, the same vital properties, nor the same life; so that the system they form is not as homogeneous in its different divisions, as the osseous, animal muscular systems, &c.

ARTICLE SECOND.

ORGANIZATION OF THE FIBRO-CARTILAGINOUS SYSTEM.

I. _Texture peculiar to the Organization of the Fibro-Cartilaginous System._

The texture peculiar to the organization of the fibro-cartilaginous system is composed, as its name indicates, of a fibrous substance, more than of a true cartilage.

The fibrous substance is as the base of the organ. We distinguish this base very plainly in the fibro-cartilages of the tendinous grooves and of the articulations, in those especially of the body of the vertebræ; it is much less apparent in the membranous fibro-cartilages. Its fibres are sometimes interlaced, sometimes parallel. In general its nature is exactly the same as in the fibrous system, hard, resisting, dense and compact, hence the very great force which the organs of this system have; hence, 1st, the solidity with which the vertebræ are kept together; 2d, the difficulty of rupturing, or tearing the fibro-cartilages of the knee, the jaw, the clavicle, &c.; 3d, the resistance which that of the radius makes to the inferior luxations of this bone, luxations which in the forced pronations of this bone have great tendency to take place, and which cannot without the rupture of this fibro-cartilage. I have seen an example of a similar displacement not reduced; the fibro-cartilage was entirely gone; 4th, by bending the true cartilages they break nearly like a radish; these organs on the contrary bend in all directions, and resist the agents that stretch them; 5th, we see men imprudently raise children by their ears, the fibro-cartilages of which easily support the weight of the whole body. I am persuaded that those of the nose would do the same. 6th. We know that in the aneurisms of the pectoral or the abdominal aorta, the bodies even of the vertebræ are much more quickly worn, and consequently resist less than the substances which unite them.

The cartilaginous portion appears to be interposed between the fibres, the interstices of which it fills. It is very evident especially in the articular fibro-cartilages and in those of the grooves; it is from it that they borrow the white colour that characterizes them, the inorganic appearance that a section of them exhibits in many places, and the elasticity which they have. Subjected to ebullition, the articular fibro-cartilages, like those of the tendinous grooves, become yellow, transparent, melt into gelatine, though with much more difficulty than the true cartilages.

As to the membranous fibro-cartilages of the ear, the nose, the trachea, the epiglottis and the eye-lids, their composition appears to be very different. The action of boiling water does not reduce them to a gelatinous state, at least in an evident manner; they remain white, soften a little, appear wholly different from a fibrous organ or the other fibro-cartilaginous organs boiled, which dissolve after becoming yellow and semi-transparent. The inspection of the ears of animals that are brought on our tables clearly proves this; I have frequently confirmed it in my experiments. I know but few of the textures in the economy that resemble this. When it has been boiled a little while, the kind of periosteum which surrounds it is detached from it; it breaks itself and cracks in many places; the rings of the trachea especially exhibit an example of this last phenomenon.

Exposed for some days to maceration, this texture, from being white, becomes of a very evident red. This colour is deeper than that which the cartilages of ossification acquire in water; does it arise from the same causes? I know not.

When the intervertebral fibro-cartilages are macerated, their fibrous laminæ take also their reddish tinge, which I have not seen in the other articular fibro-cartilages, especially in those of the knee.

Drying makes the membranous fibro-cartilages hard and brittle; they do not take then the yellow colour of the dried tendons and aponeuroses; they have a peculiar appearance.

Subjected to this experiment, the intervertebral substances acquire a remarkable transparency, different also from that of the fibrous system, without the yellowish tinge. In the first days of their maceration, these substances, when they have been entirely detached from the vertebræ, swell, rise up and form a kind of hollow cone, the summit of which is made by the middle which especially swells, and the base by the circumference which remains nearly in the natural state.

Most of the fibro-cartilages want in general the perichondrium; this is evident in those of the tendinous grooves in which the bone on one side and the synovial membrane on the other cover the organ, in those of the articulations which this membrane surrounds on both sides, and in those of the vertebræ to which only the anterior and posterior vertebral ligaments correspond. As to the membranous fibro-cartilages, there is upon them a very distinct fibrous texture; it is thick, closely united to the peculiar texture of the organ, easily seen by maceration, which whitens it in an evident manner, and which thus makes it wholly different from the fibro-cartilaginous texture which is in the middle. By cutting a fibro-cartilage of the ear, the nose, that of the epiglottis, &c. after they have remained in water, this fact is made very clear, especially during the period in which they have the redness that I have pointed out.

The fibro-cartilaginous system appears to have nearly the same relations with the digestive juices, as the fibrous and cartilaginous systems, of the nature of which it partakes; it is altered with difficulty by those juices in a crude state. Boiling, by softening, makes it yield more to their action; it becomes then more digestible. In general, it gives an aliment less proper for nutrition, than that furnished by many other systems.

II. _Parts common to the Organization of the Fibro-cartilaginous System._

The common organs of the fibro-cartilages are not very conspicuous; the cellular texture is in small quantity, and so compact as hardly to be distinguished; maceration however renders it apparent.

But little blood enters their vascular system in the ordinary state; I convinced myself of this by dissecting an animal killed for the purpose by asphyxia, a disease in which the blood accumulating in the capillaries intermediate to the arteries and the veins, towards the head especially, renders these capillaries very evident; but in inflammation, which is however rare in the fibro-cartilages, they are very much injected. We can trace no nerves in them.

ARTICLE THIRD.

PROPERTIES OF THE FIBRO-CARTILAGINOUS SYSTEM.

I. _Physical Properties._

Elasticity belongs essentially to this system. This property is very evident, 1st, in the fibro-cartilages of the ears, when we bend them; 2d, in those of the nose, when twisted in various directions; 3d, in those of the trachea, when we compress them, or after having cut them longitudinally, we separate the edges of the division, as is done in tracheotomy, when the object is the extraction of a foreign body. It performs an important use in the kind of vibration which is made in the first in the perception of sounds, in the second in the production of the voice; 4th, it is in virtue of their elasticity, that the articular fibro-cartilages serve as a kind of cushions which favour, by contracting and expanding, the motion of the osseous surfaces to which they correspond; 5th, that those of the vertebræ in particular, flattened during the day, re-act during rest, and thus make the stature in the morning something more than it is in the evening; 6th, finally in the sliding of the tendons upon their fibro-cartilages, the elasticity of these last favours the motion in an evident manner.

This elasticity of the fibro-cartilages is united to a remarkable suppleness; they bend in all directions without breaking. By the first property they resemble especially the cartilaginous system; by the second they approximate the fibrous. It is not astonishing that being intermediate to these two systems in their texture, they should be so also in their properties.

II. _Properties of Texture._

Extensibility is very often brought into action in the fibro-cartilaginous system. I have seen a polypus that had so dilated the anterior openings and consequently the fibro-cartilages of the nostrils, that their diameter was at least treble. The external and cartilaginous extremity of the meatus auditorius often exhibits from the same cause, an analogous distension. In the various twistings of the vertebral column, the portion of the fibro-cartilages corresponding to the convexity of the curvatures, is evidently elongated, whilst the opposite portion is contracted. This extensibility is moreover subjected in many cases to the same law as in the fibrous system, that is to say that it cannot be put into action but in a gradual and insensible manner.

The contractility of texture is observed when, in the cases of which I have spoken, the cause of distension disappears. Thus after the extraction of the polypus mentioned, the nostril gradually resumes its natural diameter. I have removed in a dog a tendon from its groove, by cutting it at one extremity, and drawing it by the other, so as to leave untouched and empty the sheath that contained it; this sheath and the fibro-cartilage have gradually contracted and the cavity has disappeared. In the carcinoma of the eye, in which the eye-lids were not removed, the tarsi which become much elongated with these moveable veils, gradually contract and resume their dimensions, after the extirpation of the tumour which distended them. It is necessary however to distinguish these phenomena from those which are the product of elasticity; these last are prompt and sudden; the fibro-cartilage of the ear, powerfully stretched, yields a little, and immediately goes back again; the others, on the contrary, are characterized most often by a remarkable slowness.

III. _Vital Properties._

All the vital properties appear to be but little developed in the fibro-cartilages; there is no animal sensibility or contractility in the natural state; the first appears however in inflammation. Organic sensibility and insensible contractility are only found in the degree necessary for nutrition. There is no sensible organic contractility.

This obscurity in the vital properties, gives to all the phenomena of the life of the organs of which we are treating, a remarkable slowness. I have observed that in making in the ears of a dog a longitudinal section, and afterwards uniting the wound by a suture, the skin, at the end of a few days, is entirely closed; but it is only at the expiration of a much longer time, that the union of the cartilage takes place below, as we can see by examining the parts after the union of the integuments. I presume that the same thing happened in the operation of tracheotomy formerly employed, in which the soft parts forming at first the cicatrix, keep in contact the cartilaginous semi-rings, which finally unite together.

It is also to this obscurity of the vital properties of the fibro-cartilages, to their want of energy, that must undoubtedly be referred the rareness of diseases of these organs. I know but few of the organic systems in the economy, which are more rarely affected than that of the fibro-cartilages of the nose, of the ears, the trachea, &c. Gangrene attacks them with difficulty; they are scarcely altered by it, whilst the soft parts which surround them are all already black. We know but little of the kind of fluid they form in their suppuration. The formation of pus appears to be even very rare in them, owing to their want of vital activity.

As these organs are hardly ever diseased, we can with difficulty know their sympathies; I am unable to cite an example of them.

ARTICLE FOURTH.

DEVELOPMENT OF THE FIBRO-CARTILAGINOUS SYSTEM.

I. _State of this System in the first age._

In the first periods of existence, the articular fibro-cartilages are much developed, which appears to be the effect of the size of the articulations at this period. In fact, as the extremities of the bones are larger in proportion, whilst they are cartilaginous, than when they are in the osseous state, the articulations are also proportionally larger, and the organs they contain more developed.

The fibro-cartilages of the grooves, which are found almost all, as we know, situated at the extremities of the long bones, are not, in the first age distinct from the cartilages of ossification, which then form these extremities. Confounded with them, they exhibit no line of demarcation when we cut the lines at that place. This state continues until complete ossification; then the fibro-cartilages of the grooves remain insulated like the cartilages of the osseous extremities.

The interposed gelatinous portion appears to predominate, in childhood, over the fibrous portion in the articular fibro-cartilages and in those of the grooves. It is remarkable in the intervertebral substances, in which this kind of mucilage which occupies the centre, is as to quantity in the inverse ratio of the age, and in which the fibres are also more developed. On the pubis, the whole is almost homogeneous in the fœtus; the transverse fibres do not become very apparent till a more advanced age. The articulations of the knee, the jaw, &c. have in their fibro-cartilages, the same arrangement. Ebullition extracts from them then a much greater quantity of gelatine; they have more the smooth appearance of the cartilages.