General Anatomy, Applied to Physiology and Medicine, Vol. 2 (of 3)

by Xavier Bichat

II. Common Parts which enter into the organization of the Osseous System.

The ancients ranked the bones among the white parts, among the tendons, the cartilages, &c. It is sufficient however to examine the interior of them to see, by the redness that distinguishes them, that much blood enters them. This blood penetrates in three orders of vessels; one belonging to the medullary cavity of the long bones, another to the texture of the cells, and the other to the compact texture. These two last orders distributed in the osseous texture, appear to be especially destined to deposit the phosphate of lime; for in the cartilages of ossification, the white vessels alone carry the gelatine; in other cartilages it is the same; so that I think that this kind of vessels is also destined in the bones which are perfectly formed to nourish their cartilaginous parenchyma, whilst the red vessels belong more to their calcareous portion.

Each medullary cavity has only one vessel, and only one foramen of nutrition. This vessel has a diameter proportioned to that of the bone which it penetrates, and in which it is divided immediately into two branches, without permitting any ramification on the compact texture. These go in an opposite direction to the two extremities of the bone, ramify ad infinitum in the medullary organ, and their last branches are lost in the commencement of the texture of the cells, where they anastomose with the vessels of this texture; that which occupies the medullary cavity under the name of reticular, and the internal surface of the compact texture, receive also some branches. A vein everywhere accompanies the artery, and follows the different distributions of it.

The vessels of the second order belong to the texture of the cells of the long, flat and short bones; they are equal in number to the foramina of this texture, and ramify on its cells; they communicate with those of the marrow and of the compact texture. At death, the small arteries in general remain full of red blood, which indicates their course which their minuteness would conceal, and which injections can rarely demonstrate with accuracy. The accompanying veins of these arteries can hardly be seen.

The blood-vessels of the third order are only the last ramifications of the arteries surrounding the bones, ramifications which enter in great number the compact texture, and stop there. The existence of these vessels may be proved in different ways. 1st. By detaching the dura mater from the internal surface of the cranium, many small sanguineous drops prove their rupture. 2d. By raising on a subject of a middle age the periosteum, we make the same observation. I have remarked that these experiments succeed especially on those that have been drowned, or on animals destroyed by asphyxia, on account of the great quantity of blood their vessels contain. 3d. If we fracture a long bone in the middle, the compact portion, which forms the medullary canal, exhibits small reddish striæ, which are nothing but these small vessels still full of blood, and of which we thus discover a greater or less number, according to the manner in which the blood was arrested in the capillary system at the instant of death. 4th. The saw-dust of the compact texture in living animals is red, though less evidently so than that of the texture of the cells; a proof that these vessels have been divided.

The vessels of the bones are very numerous in childhood; they diminish in the adult, and become scarce in old age. The facility of the formation of callus follows the same proportion in the different ages of life. Often in affections of the osseous parenchyma they have a remarkable development, which much exceeds their natural diameter. Osteo-sarcoma, spina-ventosa, &c. exhibit this, which is much oftener observed in cancerous tumours than any other.

These vessels communicate with each other by numerous anastomoses; this is what we see especially in the long bones, between those of the medullary organ and those of the texture of the cells. By these communications, they mutually assist each other's functions. I have seen the nourishing foramen of the tibia completely obliterated in a body that I injected. A sort of cartilage filled this foramen; the artery formed a real ligament. Yet its bifurcation in the medullary canal was found very well injected, and besides no alteration appeared in the nutrition of the medullary organ, which had probably received as much blood as usual. I found nothing in the neighbourhood of the foramen, which showed the cause of this obliteration, which an exostosis, an affection of the periosteum, or an inflammation can very easily produce.

On the other hand we know that very considerable osseous layers are often taken from the extremity of the long bones by caries, which consequently destroys all the vessels corresponding to these layers, and yet the bone beneath lives, principally by the blood that it receives by the extremities of the artery of the medullary organ. This is nearly what happens to the long bones in the first age, in which the cartilaginous extremities have not vessels of the second order, and in which consequently almost all the blood comes from this same artery of the medullary organ; thus it is much larger in proportion, and the foramen which receives it much more considerable.

Nothing is yet known upon the systems of absorbent and exhalant vessels of the bones, and we can reason upon this point only from analogy. Besides the nutritive process evidently supposes them there.

As to their cellular texture, it appears to be almost nothing; we can even say that in whatever place we break the compact fibres or those of the cells, its filaments are not distinct; but it is their dense and compact texture that conceals them from us. In fact, 1st, when this texture is softened, and the bone has become flesh, as it is called, the cellular texture is very apparent there. 2d. The fleshy granulations, rising on places that have been fractured or laid bare, are only the extension of the cellular texture which has too much calcareous substance to allow it to be seen in the natural state. 3d. After having removed from a fresh bone all this substance by an acid, I have sometimes observed cellular filaments by separating the cartilaginous fibres which form the parenchyma that is left. 4th. When we boil this cartilaginous parenchyma in order to extract the gelatine from it, there remains portions of membranes which are evidently cellular.