Of Union by Adhesion.

397

plete union appears to have taken place: and when in a day or two afterwards the red edge of the clot peels off, cuticle is found below it; but the linear surface remains of a darker hue for several days.

When a small portion of the body is entirely separated, as for instance, the tip of the ear, the half of a finger, if it be immediately re-applied, mechanical adhesion takes place in a similar way, and the part lives...

When large cut surfaces are brought in contact, as after the removal of a breast, or the amputation of a limb, it appears that in general union is at first mechanically effected by the coagulated blood; but in most cases the inflammation, which follows, produces a tumefaction and a flow of various secretions, which prevent the first union holding more than partially. After a few days, the surface of the wound appears covered with a soft layer of vascular flesh, called granulations, from which pus is secreted; and which rising fill the cavity of the wound, and are converted into the nature of the substances, which they unite..

Pus is a viscid straw-coloured fluid, of the specific gravity of 1050, it coagulates when raised to the temperature of 112°, or when mixed with muriate of ammonia: its colour, depends upon a number of globules, sensibly larger than the globules of the blood; it appears from the researches of Sir E. Home, that these globules are formed by chemical attraction in a fluid, which is limpid and colourless when first secreted.

When a considerable portion of skin is removed, the cellular membrane inflames below the blood which stif fens on the raw surface, and secretes pus, and forms a crop of granulations; these gradually rise to the level of

and higher than the surrounding skin; the secreting surface appears to diminish daily, and becomes, in patches, or at its edges, converted into a tender whitish substance, which thickening becomes opake and forms a cicatrix; on the day that a portion of a cicatrix is completed, it is insensible; about a fortnight afterwards it feels, if prickedwith a needle.

Thus in the formation of a cicatrix after destruction of the skin, the new material is produced not by the neighbouring cutis, but by a growth from the subcutaneous

texture.

When tendons, or nerves, cartilages, or bones, are divided or broken across, the process of their re-union does not resemble the adhesion of divided skin, but has more in common with the growth of a cicatrix. The disjoined surfaces do not cohere immediately, but through the intervention of a third substance, which appears produced from the neighbouring cellular texture.

If the tendo Achillis be examined in a dog forty-eight hours after division, upon removing the skin, the subjacent cellular membrane, that surrounds the tendon, ap pears loaded with coagulable lymph, and extravasated blood. Upon making a longitudinal section of the thickened substance, the cut ends of the tendon contained within it are found to be about an inch apart, but connected together by means of coagulated blood, and swollen cellular texture.

If the tendo Achillis be examined seven days after division, the ends of the divided tendon are found united by an intervening substance of greater thickness than the tendon itself, that is readily separable from the skin.

Re-union of Tendons, and of Nerves.

899**

and subjacent parts. Upon a longitudinal section being made, the intervening substance appears of a dark red colour, firm, and to a certain degree elastic: it coheres, in some parts firmly, in others slightly, with the cut ends of the tendon, but strongly and inseparably with the cellular sheath of the tendon, which is discoloured for some distance: so that either end of the tendon admits without much force of being displaced from a socket in the intervening substance.

At seventeen days after division, the intervening substance is found diminished in thickness, firmer, paler, and inseparably coherent with the cut ends of the tendon, the nature of which it gradually assumes.

When a nerve is divided, the process, by which its ends are joined, exactly resembles the mode in which tendons unite. Without detailing the appearances on dissection at an earlier period, let me describe the state of the part, at the time when the return of its function first manifests itself.

The infraorbital nerve was divided on one side upon the cheek of a cat, and a portion about a line in length was removed from it. The skin of the upper lip imme diately lost sensation. The wound, however, readily cicatrized; and by the twentieth day sensation appeared entirely restored. Upon examining the part at this period, the nervous fibrils appeared to be united by a thick layer of tough gray semitransparent substance. On making a longitudinal section of this substance and of the nervous fibrils which entered it, the extremities of the divided filaments appeared nearly two lines asunder, and firmly coherent with the intervening substance : here and there a whitish fibril seemed to extend further

400

Re-union of Cartilage.

into the connecting medium, but no restoration of continuity between the nervous fibrils was observable.

When the portio dura is divided on the cheek, it unites in a similar manner; but the nerve does not begin under four weeks to resume the office of transmitting the influence of the will. About this time, however, the eyelids, which hitherto have been motionless, are observed to be slowly and inperfectly drawn towards each other, whenever the surface of the conjunctiva is touched.

If the cartilage of a rib be examined in a dog fortyeight hours after division, the cut surfaces of the cartilage are not found to have undergone any change: they are held together by a loose capsule formed by the surrounding parts. Towards the seventh day, this capsule has assumed a dense elastic texture, and distinctly includes the adjacent cellular membrane and muscular substance. The edges of the cartilage appear rounded off, and a slight exsudation of lymph seems interposed between the disjoined surfaces. On the seventeenth day the appearance is much the same; the intervening substance, which has acquired consistence, is continuous with, and appears derived from the capsule. About the twenty-eighth day, the intervening layer of lymph is found adhering to and loosely uniting the opposite cartilaginous surfaces.

The changes, which attend the re-union of a broken bone are even more elaborate than those, which occur in the preceding instances. The most valuable observations, which have been published upon this subject, are by M. Dupuytren.

If a fractured limb be examined within forty-eight hours after the injury, the periosteum is found to have

been stripped irregularly from the broken ends of the bone: the cancelli of the bone and the neighbouring soft parts seem in a state of ecchymosis; the quantity of blood, however, effused from the ruptured vessels is generally inconsiderable.

About the fourth day a change is found to have supervened; the parts adjacent to the broken ends of the bone have become condensed and indurated, and form a firm capsule which contains the broken extremities. The thickening includes every neighbouring texture: the muscles, tendons, and cellular membrane, for the extent of a few lines seem condensed into one tough elastic mass. During the next fortnight this capsule becomes of greater firmness, assuming the character of cartilage : at the same time lymph is frequently found to have exsuded around the broken ends of the bone.

After the third week the muscles and tendons gradually become again distinct, or disengaged from the thickened capsule, in which ossification soon commences: so that at the expiration of four or five or six weeks, the broken ends of the bone are fixed in some sort of apposi tion by an osseous case extending from the one to the other, having its adhesion at some little distance beyond the fractured edge. The only union between the extremities of the bones, that hitherto has taken place, is by soft substance, which comprehends the organized clot of blood, the lymph effused, and productions from the capsule, which have grown together and coalesced.

During the interval between the sixth week and the fifth or sixth month, the process of ossification extends from the capsule, to the soft substance which directly unites the broken surfaces. At the same time the cap