We have now described the process of re pair in wounds in the skin, with loss of the entire substance of the cutis. When the de struction has been more superficial, the process of restoration is more rapid, and the result more perfect, inasmuch as the part upon vvhich the burden of repair devolves, is the inner layers of the original cutis, a part much more highly organized and more equal to the task than the cellular tissue.* In wounds which are united by the first intention, the stage of suppuration does not take place. The sub stance which would have formed suppurating granulations here becomes an immediate means of union, and the only portion of new skin formed is in the mere line where the divided edges met, a line always visible by the white colour before mentioned.
In the healing of ulcers in any of the mucous membranes, the process would appear to go on much in the same way as on the skin. Granu lations shoot up from the bottom of the ulcer ; the surrounding healthy membrane is drawn inwards by their contractile power, and the edges of the ulcer are turned in and become continuous with the new membrane, which at length covers the ulcer. When the destructive process has merely gone through the mucous membrane, the granulations shoot from the mus cular coat, and the contraction is of course ex ercised only upon the surrounding mucous coat; but when the muscular tunic is destroyed, the granulations grow from the bottom of the wound, that is, from the cellular tissue in contact with the peritoneum; but the contraction of the sur rounding parts now diminishes the circumfe rence of the ulcer very considerably by puck ering up this thin layer of membrane, so as to give it externally an appearance as if a small portion of the intestine had been taken up by the forceps and tied with a ligature on the in side.* When the process of repair is com pleted, a fine web-like production from the edges of the ulcer overspreads its base, and forms fine wrinkles converging towards its centre. This production is destitute of villi, and slightly depressed. When the ravages of the disease have been very extensive, the cica trix is covered by puckered cellular tissue, formed of white thread-like filaments, crossing each other in all directions, and leaving pitted interstices.t When the ulcer was small, the cicatrix has sometimes a considerable resem blance to the scar of small-poxl That cicatrization takes place in the lungs after tuberculous excavations, the observations of Laennec§ and Andra] among others, have put beyond a doubt ; and since these patholo gists have made public their observations of the fact, and pointed out the signs by which it may be known, most observers have borne tes timony to the accuracy of their statements. According to Laennec there are three ways by which this desirable object is accomplished ; one, by the walls of the cavity becoming lined with a membrane of a semicartilaginous struc ture and smooth polished surface, which seems often continuous with the lining mem brane of those bronchial ramifications which open abruptly into the cavity. This state of
the restorative process constitutes a sort of in ternal cicatrix, analogous to a fistula, and is in many cases not more injurious to health than the species of morbid affection just mentioned. The second mode of cicatrization consists in the obliteration of the morbid cavity by adhe sion of its sides. In the complete state they exhibit, when cut into, a band of condensed cel lular substance or of fibro-cartilaginous struc ture. The bronchial tubes which run towards this structure are obliterated as they reach it, and there is generally an unusual quantity of the peculiar black matter of the lungs in the patts bordering upon the cicatrix ; and where this is the case, the structure of the lungs is more flabby and less crepitous than natural. These internal cicatrizations are indicated on the surface of the lung by a depression of the pleura, the depth of which corresponds with the size of the previous excavation, and is sometimes so deep as to form a large over lapping prominence of the neighbouring sound parts. Here we have another instance of the same contractile tendency in newly formed structures, which is so striking in cicatrizations of the skin; a tendency resulting from the gene ral law by which the labour of restoration is, as much as possible, spared to the animal system.
The third species of cicatrix in the lungs is that formed by the fibro-cartilaginous walls in creasing in thickness till they fill up the cavity, thus leaving a blueish or greyish white mass, in which large bronchi terminate abruptly as in the preceding case. Cicatrices of the two last kinds are not uncommon.s In the healing of common abscesses, whether in the subcutaneous cellular tissue or in the more deep-seated parts, the mode of cicatriza tion is much the same as in the second species just described. As the fluid contents are re moved by evacuation, the cavity of the abscess is diminished in extent partly by the contrac tion of the surrounding tissue and partly by the granulations arising from the sides of the ca vity, and as the opposite sides are thus brought in contact they adhere, and at length leave a fibrous cicatrix, whitish and more dense than the surrounding cellular tissue. It is remark able that few or no abscesses granulate till they are exposed, and that after they are opened there is one surface that is more disposed to granulate than the others, which is the surface next the centre of the body in which the sup puration took place. The surface next the skin hardly ever granulates, but on the contrary has an ulcerative tendency The proximate cause of this remarkable difference is not evi dent, but the utility of it in the healing of the abscess is clear and striking.t We have now considered the processes by which nature repairs the breach in the healthy structure ; let us in conclusion shortly examine the characters which mark the cicatrix when completed. This new formation, though in many points it resembles and fulfils the func tions of the old and perfect skin, yet differs from it in many material respects.