1. Congestion, - Hemorrhage, - Anoemia

A passive congestion, limited to certain parts of the skin, may be constantly observed on the dead body. It is seen, too, on the whole integuments, as a dark redness, with a blue or black tint, in the course of acute and chronic adynamic diseases, and in most instances of agony: it is very marked in parts of the body that are at a distance from the heart, and becomes extremely so if there be any mechanical interruption of the circulation.

Congestion in a higher degree gives rise to hemorrhage into the tissue of the skin; sometimes in small circumscribed spots, sometimes in streaks, and sometimes to a large extent; it may take place upon the surface of the corium beneath the epidermis, or in the tissue of the former; and, in the latter case, it is usually associated with hemorrhage into the subcutaneous tissue also. The bloody spots in Werlhof's morbus maculosus1 and in scurvy, the petechiae in the course of typhus and typhoid fevers, etc, are instances of such hemorrhage. Its occurrence is facilitated by delicacy and susceptibility to injury on the part of the walls of the capillary vessels, and by a tendency to transudation on the part of the blood.

Anaemia of the general integuments is a local part of a universal anaemia, and is always accompanied with collapse and pallor of the skin; the pallor acquires a waxen character when the skin is delicate, and especially if at the same time it be rendered tense by the presence of fat or oedema.

2. Inflammations

Inflammation of the skin (dermatitis) may result from very various external influences, which are but partly known, and be an idiopathic, substantive disease: it also very frequently occurs as a symptomatic and dependent affection, - a reflex of other morbid processes. Regarded in an anatomical point of view, it is found sometimes diffuse, and extending over large tracts of skin; sometimes it is circumscribed, and confined to one or more small spots.

In the first form, the true cutis is the part attacked, and sometimes only its external layer and papillae - erythema: at other times the deeper layer also, that is to say, the whole thickness of corium is affected; and that constitutes phlegmonous inflammation.

From it, and particularly from the erythematous form, there are several transitions to the circumscribed inflammation of skin. The simplest form of the circumscribed is furuncular inflammation.

Allied to this are several of the acute and chronic exanthematous processes.

I proceed now to speak of them in detail.1