1. Defect And Excess In Development

Congenital deficiency of the integuments is extremely rare, whether extending over the whole, or only over parts of the body. An instance of the former kind was observed by Bartholin; and Cordon met with a case in which the skin was wanting from the knees to the toes.

Upon the skin of new-born children there are often seen circumscribed spots, the complete development of which has been arrested by some pressure during foetal life. It is uncommonly thin and transparent, and its defect appears proportioned to the closeness of its union with the fibrous and serous membranes beneath it. Instances of this deficiency are seen in hemicephalus, in spina bifida, and in several of the fissions of the anterior wall of the trunk. A congenital defect of another kind has also been met with, in which the general sac of the integuments is so small at particular spots as, according to an observation of Otto's, on the lower extremities of new-born children, to form strictures.

An acquired partial deficiency of skin is produced by wounds, burns, suppuration, sloughing, and other causes from which losses of substance ensue.

A preternatural growth of skin may occur as a congenital condition and produce an increase in the capacity of the general sac. The additional skin is loose and movable, and hangs in folds and appendages; thus at the end of the spine it forms a sort of tail. Instances of an ac-quired excessive growth of skin are furnished by several of the encysted tumors: they usually present here and there spots that resemble cutis; and they are the tumors in which the hair that grows in cysts is chiefly found.

The same class includes all cases of regeneration of skin, whether destroyed by wounds, burns, or cauterization, by the various ulcerative processes, or by mortification. The loss is in general easily repaired, but always in a form that differs more or less from the original skin. The new structure consists of a dense cellular layer of various thickness and of epidermis; but it has neither papillae, sebaceous glands, hair follicles, nor sudoriparous glands. It is usually tightly stretched and whiter than natural: sometimes it is smooth and shining, sometimes it has a rugged and uneven, stellate, knitted, or areolar surface: very often it is but slightly movable over the subjacent structures, and occasionally is intimately united with them. It lies beneath the level of the surface of the rest of the skin.

2. Anomalies In The Size (Capacity), The Thickness, And The Form Of The Sac Of General Integuments

In regard to size, the congenital anomalies already mentioned belong also to this section. Further instances of acquired anomaly in this respect are found, on the one hand, in the contractions, shortenings, etc, which result from various losses of substance and cicatrization consequent upon them; and on the other hand, in the dilatations to various amounts, which are produced, for the most part, by gradual distension or traction. Moreover loose, or soft and elastic, pendulous growths of various sizes are formed upon the skin; within an attenuated corium they enclose a delicate cellular tissue, most of which is newly formed (molluscum simplex), and occasionally they contain also some adipose tissue, which has protruded through the meshes of the deeper layer of the corium.

The form of the cutaneous sac is disfigured not in these cases only, but also in a more or less striking manner when there exist, or have existed, many diseases of its texture.

The skin deviates from its natural thickness in both directions.

An abnormal thickness is sometimes occasioned by congestion or inflammation of the skin, and attended with expansion and moistness of its texture: sometimes it is the result of a continuance or repetition of the same processes, in which case the deposition of their plastic product in the tissue of the skin adds condensation of texture and firmness to the increase of its thickness: sometimes the cause is hypertrophy, which again may chiefly affect the papillae or the deeper layer of corium: and, lastly, it is sometimes the effect of the development of adventitious growths in the corium.

Hypertrophy of the skin is in many nsevi a congenital affection; but more frequently it is extended over wide tracts of skin, and is a result either of stagnation in the venous or lymphatic system, or of habitual inflammatory processes, particularly those of exanthematous and impetiginous nature. It accompanies, on the one hand, under the name of elephantiasis (Pachydermia of Fuchs), exuberant growths - hypertrophies - of the subcutaneous cellular tissue; and on the other hand, most probably all, but particularly the more important, anomalies of the secretion of epidermis.

The form it presents is very various. Sometimes the hypertrophied portion of skin is smooth, sometimes the irregularity of the hypertrophy renders the surface rugged and tuberous: the skin may be movable over the subjacent structures, but in advanced degrees of the disease it is stiff and adherent, especially to fibrous structures; and the diseased part, the leg for instance, then becomes immovable; its muscles, and even its bones shrink, and the articular extremities of the latter become anchylosed.

The papillae become hypertrophied in various degrees and forms: sometimes they resemble the villi of the intestines: sometimes they constitute excrescences which are attached by a pedicle, and truncated, or split like a tassel at their free extremity, or are sessile, rounded, and like a mushroom, etc. Hypertrophy in these forms are seen on naevi, and on portions of skin which have long been withdrawn from the atmospheric influence, and exposed to that of warmth and moisture, or have been covered with emollient and slightly irritating plasters, etc. It is noticed also in parts at which the skin has been in contact for a lengthened period with its own secretion, as it is in the deep fissures between the rolls and knots of skin in cases of elephantiasis; in the neighborhood of chronic ulcers; and on spots of skin covered with scaly eruptions: the hypertrophy of the papillae is very marked also in decided cases of ichthyosis. Lastly, it is found, - at least it is assumed as probable, - that the genuine common wart (Verruca vulgaris) is a hypertrophy of the papilla beneath a very thick layer of epidermis, which dips in sheathlike processes into the deeper parts of the growth. Warts are exceedingly common upon the hand, especially on the fingers; occasionally too they occur in other parts, as, for instance, on the forearm.

The skin may yield to distension or traction from within, and become unnaturally thin. Instances of this are met with in cases of dropsy of very dilatable serous sacs, of the peritoneum, for instance, or the tunica vaginalis testis: in anasarca; or when large tumors are growing in the subcutaneous cellular tissue. The fasciculi of fibres that compose its deeper layers separate from one another, its exterior dense stratum becomes so thin as to be transparent, and even at last to suffer gradually a solution of continuity. In the foetus, under these circumstances, it assumes the character of a serous or a fibro-serous membrane, and uniting intimately with the subjacent membranous structures, appears, as was before said, to be deficient at such spots.

When long-continued pressure is exerted upon one fixed spot of skin, such, for instance, as is produced by a tumor, complete atrophy sometimes takes place: the skin is gradually reduced to a thin vascular stratum, which secretes a viscid epidermal mucus, and at length is completely perforated.

Primary atrophy of the general integuments, strictly speaking, does not occur; but they become atrophied rather frequently as a secondary consequence of repeated attacks of inflammation, especially those of impetiginous character. The skin becomes thin and vascular, acquires a dirty brownish or bluish color, and generally gives way upon very slight injury; at last it changes into a dense white cicatrix tissue.

3. Anomalies In Consistence

Laxity of the corium exists congeni-tally in cases of naevus; and congestion or inflammation will, after birth, bring on a state in which the texture of the skin is loosened or expanded. It becomes loose also in parts which are withdrawn from the air, and continually exposed to moisture; in parts where perspiration is constantly taking place, and in the hands of little children, who have a habit of sucking them, etc. But, again, cutaneous tissue is sometimes increased in density and hardened; it becomes hypertrophied and thickened, or without being thickened, it may be hypertrophied, dry, and harsh.

A certain amount of softness of the skin, as well as of hardness and dryness, is sometimes merely an individual peculiarity of the whole organ.

4. Solution Of Continuity

The general integuments are, in the first place, liable to very numerous and very varied mechanical injuries: solutions of continuity may also be produced in different ways by the action of chemical agents upon the skin; and, lastly, the same result ensues from the many ulcerative processes that take place in this structure. We must, however, notice the various forms of separation of the epidermis from the corium (spontaneous excoriations), that are occasioned and kept up by diseases of the skin, the spontaneous lacerations already alluded to, that are produced by extreme distension, and the fissures extending into the corium, which, in many chronic diseases, proceed from the splitting of an extremely dry epidermis (chaps - Rhagades). They heal in the usual manner, either by immediate cohesion of the lips of the wound, or by granulation and cicatrization.