Part 21

Observe the bones in the midst of all that general sympathetic derangement of the systems in which life is very active; they undergo no alteration; their life, more slow than that of the other systems, is not connected with these phenomena which have an acute character; neither is that of the cartilages, the fibro-cartilages, the hair, the aponeuroses, &c. All these systems, remarkable by the same character of vitality, do not respond to the acute affections of the other systems; they are not sympathetically affected, during these affections, at least in an evident manner. Observe all the acute fevers; their numerous phenomena have an effect only upon those systems in which life is very active; those in which it is distinguished by an opposite character, have uniformly no connexion with these phenomena; they are, if we may so say, calm and tranquil in the midst of the tempest which agitates the others. Let us take for example the different eruptions that appear in fevers; it is upon the skin, the mucous surfaces, &c. that they come; they arise during the fever and they disappear with it; now the bones, the cartilages, &c. could not, from their kind of life, admit of this sudden origin and disappearance.

It is then in the slow and chronic affections that we must seek for examples of sympathies of the osseous, cartilaginous systems, &c. In the first stages of the venereal disease, in which it is marked only by acute symptoms, or in which at least its progress is not very slow, as when it appears in buboes, in inflammations of the urethra, &c. it has no influence upon the osseous system; it is only when it is of long standing, when it has, as it were, degenerated, and become chronic, that it makes the bones the seat of pains, of different tumours, &c. Besides, I do not know, that we have yet thoroughly analyzed the osseous sympathies. I have shown only their general character. We shall understand them better, when we have given more attention to the relation that there is in diseases between the affection of each organ, and its kind of vitality.

Seat of the Vital Properties.

The bones penetrated by saline substances which tend continually to obey the laws of affinity and attraction, and to make these laws predominate over those of sensibility and organic mobility, seem to hold a middle place in living bodies, between these bodies and inanimate ones. There is truly but one part of their osseous texture which partakes of the vital phenomena, viz. their cartilaginous substance; the other part or calcareous substance is foreign to them; thus the proportion of each of these substances determines in the bones their degree of life. In infancy, in which the first predominates, in the early stages of the formation of callus, in which it is exclusively found, in the softening of the bones in which it remains almost alone, all the vital phenomena become more evident and more powerful. On the contrary, as age accumulates in the bones the saline substance, as in certain animals this accumulation takes place by the natural laws of ossification in some external portions of the system with calcareous base, as in the horns of stags, the shells of crustaceous animals, &c. so life is, if we may so say, successively destroyed in the bones; it becomes nothing, when this calcareous portion predominates considerably; this is what happens in the necrosis which produces the fall of the horns, the casting of the shells of crustaceous animals, &c.

Besides, that which shows the vital energy in an organ, is the rapidity with which inflammation goes through its periods in it, and the frequency of this affection, &c. Now in the bones inflammation is so much the more rapid, in proportion to the greater quantity of cartilaginous texture they contain; observe the periods of the formation of the callus in the different ages, periods which are determined by the duration of the inflammation necessary for its formation, you will see that in infancy they are short, that they are much longer in old age, and that often even consolidation does not take place, whilst it is effected with facility in all the soft parts. The general weakness no doubt of all the vital forces which takes place from the effect of age is one cause of this slowness and this rapidity in the formation of the callus at the two extreme periods of life; but the different proportions of gelatinous and calcareous substances contribute much to it also; for when we compare other cicatrices with this, the cutaneous, for example, we see that age establishes in them an infinitely less sensible difference as it respects the slowness and rapidity of this reunion, than in the osseous system. The bones have not sufficient life to inflame and unite, like the skin, the muscles also exhibit this phenomenon in a very evident manner. I have seen an old man, the neck of whose fractured thigh-bone remained a long time without reunion, and in whom a wound of the face was healed very speedily by the first intention.

Finally, there is a simple experiment that I have often made, and which proves as well as the preceding facts, that the cartilage is truly the animal part of the bone. We know that one of the great attributes of animal substances, is to contract and exhibit the horny hardening when burnt; now when the bone is penetrated with its earthy salt, it has not this kind of combustion; deprived of this salt by an acid, the cartilaginous parenchyma which remains burns in this manner. The flat bones in infancy in which this parenchyma predominates, exhibits also this phenomenon in burning; it forces the calcareous portion, which is in small quantity to obey the impulse that it gives it, and turns it in various directions; but in the adult in whom the calcareous portion is the largest, the bone remains unmoved while the fire penetrates it, and its whole cartilage is taken away, without its fibres being able to obey their tendency to the horny hardening which combustion imprints upon them.

ARTICLE FOURTH.

OF THE ARTICULATIONS OF THE OSSEOUS SYSTEM.

All the bones are united together, and thus form the skeleton. The manner of their union varies, but whatever it may be, it is known under the general name of articulation.

I. Division of the Articulations.

All the articulations can be referred to two general classes. Mobility is the character of the first, immobility that of the second.

One belongs to all the bones which serve for locomotion, to some of those destined to internal functions, as the ribs, the lower jaw, &c. The other is especially met with in the bones, the union of which forms the cavities designed to defend the organs; this we see in the head, the pelvis, &c.

Moveable Articulations. Observations upon their Motions.

I divide moveable articulations into four kinds, the characters of which are borrowed from the different motions they execute. To understand this division, it is necessary previously to know the motions of the articulations in general. These motions can be included under four species, which are, 1st, opposition; 2d, circumduction; 3d, rotation; 4th, sliding.

1st. The motion of opposition is that which is made in two opposite directions, for example, from flexion to extension, from adduction to abduction, and vice versa. This motion is extensive or limited; extensive when it is made in all directions, first in the four named above, then in all the intermediate ones; limited, when it only takes place from flexion to extension, from adduction to abduction, &c. The thigh in its articulation with the pelvis enjoys an extensive motion of opposition. The tibia in its articulation with the femur has a limited motion of opposition.

2d. Circumduction is the motion in which the bone describes a kind of cone, the summit of which is in its superior articulation, and the base in the inferior; so that it is found successively in flexion, adduction, extension and abduction, or in abduction, extension, adduction and flexion, according to the motion by which it begins, and that moreover it goes through all the intermediate directions. Hence we see that circumduction is a motion composed of all those of opposition, and in which the bone, instead of moving from one direction to an opposite one, as in the preceding case, moves from one direction to another nearest to it, describing thus by its extremity a circle which is the base of a cone of which I have spoken, and which is so much the greater as the bone is so much the longer. We easily understand that among the bones, those only whose motion of opposition is loose, enjoy that of circumduction.

3d. Rotation is wholly different from the preceding motion. In this there was locomotion, a moving of the bone from one place to another; here it remains always in the same place; it only turns upon its axis. The humerus and the femur enjoy this motion which is simple.

4th. Sliding belongs to all the articulations. It is an obscure motion, by which two surfaces go in an opposite direction, by sliding as it were upon each other. In all the other motions, this is met with; but it often exists without them.

It is easy to understand, from these views upon the articular motions, the division into genera of the class of moveable articulations. In fact, there are articulations in which all the motions are united; in others, there is no rotation; in many rotation and circumduction are wanting, and opposition exists only in one direction; some have only rotation. Finally, there are those in which rotation, circumduction and opposition are nothing, and sliding alone remains.

Hence we see that nature moves here as elsewhere by gradation, that from the most moveable articulations to those that are the least so, there are different degrees of decrease, that she descends gradually to the immoveable articulations, that she is finally reduced to the motion of sliding alone, like that which exists at the carpus, the tarsus, &c. There is even an intermediate one between sliding and immobility; it is the articulation of the symphysis pubis; which can be considered with that of the humerus as forming the two extremes of the series of moveable articulations.

All the articulations of which I have spoken are with contiguous surfaces; this is the general character of those which are moveable. There is however an exception to this rule; it is the articulation of the body of the vertebræ, in which there is continuity and mobility. The symphysis pubis is also in part continuous in its surfaces, and yet has sometimes obscure motions. Hence arises a division of the moveable articulations, into those with continuous surfaces, and into those with contiguous ones.

Immoveable Articulations.

The immoveable articulations are sometimes with surfaces inserted into each other, as the bones of the cranium, in which many projections and depressions reciprocally receive each other; sometimes with surfaces in juxta-position, as in the articulation of the temporal with the parietal, the two superior maxillary bones with each other; sometimes with implanted surfaces, as in the teeth.

All the different divisions that I have mentioned will be easily understood by the following table; it is not the same as that which I have given in my treatise on the membranes; I think it presents a classification a little more useful in this, that it offers for a characteristic two things essential to be known in all kinds of moveable articulations, viz. 1st, the relation of the articular surfaces which characterizes the orders; 2d, the number of motions of each which distinguishes the genera. There are no orders in the immoveable articulations because, except the relation of surfaces, the articulations have not differences sufficient to occasion them to be sub-divided.

Table of the Articulations.

┌ CLASSES. ┌ ORDERS. ┌ GENERA. │ │ │1st. Extensive Opposition, │ │ │ Circumduction and │ │ │ Rotation. │ │1st. With │2d. Extensive Opposition │ │ Contiguous │ and Circumduction. │1st. Moveable. │ Surfaces. │3d. Limited Opposition. │ │ │4th. Rotation. │ │ └5th. Sliding. ARTICULATIONS. │ │2d. With Continuous │ └ Surfaces. │ │ ┌1st. With Surfaces │ │ in juxta-position. │ │2d. With Surfaces │ │ inserted └2d. Immoveable. │ into each other. │3d. With Surfaces └ implanted.

After having thus divided the articulations, let us offer upon each class some general observations. But let us first remark that the preceding table, considered in respect to the moveable articulations with contiguous surfaces, indicates perfectly the disposition of these articulations as to luxations, which are so much the more frequent as the motions are more extensive. The first genus is the most exposed to it, the last the least so; and the others are more or less so according to their distance from the first.

II. Observations upon the Moveable Articulations.