It may be one of the forms in which secondary suppuration presents itself, or it may give rise to secondary suppuration else where. In both cases the characters of pyEemia may be traced in addition to the cellular inflammation; the local abscesses, the inflamed absorbents, and the profuse perspiration, suggest to the observant practitioner what is going on.
In its progress suppuration always supervenes; rigors, which have been absent since the commencement of the attack, recur, and are followed by sweating ; the inflamed surface becomes less angry, and assumes a more livid color ; the tension subsides, and is followed by what is called a " boggy" feeling, which is partly produced by superficial oedema, partly by purulent infiltration and deep-seated fluctuation.
In tracing the main features by which diseases of the skin are to be dis criminated, and applying to them the rules of diagnosis, we are in great mea sure restricted to the distinct objective phenomenon which each case presents in addition to its other and more general symptoms. cases the in spection of the eruption is all that is wanted to determine its classification ; and this is especially true of what may be called typical examples, but quite as frequently our judgment is influenced by other circumstances which the history of the case records. Practical habitude can alone give the power of determining which among these have any direct bearing on the cutaneous affection ; and the educated eye can often determine the class to which any case belongs from its general aspect and history, without entering on a minute examination of its specific character.
When seeking for the solution of a difficulty, subordinate matters must not be neglected, such as the station in life, the probability of hereditary taint, of unsuitable food, or of exposure to infection, which the appearance and manner of the patient suggest. With this object the physician may be in duced to ask many questions which seem to have little to do with the skin ; unquestionably in a great many instances it is true that the more correct the history of the patient's past life, the more certain is the diagnosis of any par ticular ailment. I will add a few illustrations of the manner in which these additional facts afford hints for our guidance in diagnosis.
A febrile state more or less accompanies erythema and roseola, but seldom coexists with urticaria, and its comparative mildness separates these from erysipelas, phlegmon, measles, and scarlatina. It distinguishes the acute from the chronic form of eczema, and marks the boundary very often between eczema impetiginodes and true impetigo. It draws an equally clear line of demarcation between pemphigus and rupia. It is always present with herpes, but when the fever is severe, the eruption is certainly only subordinate to some internal disease. Insufficient nutriment or exhaustion of body cause many of the varieties of skin disease to assume a suppurative character ; the bearing this in mind will often lead to the discovery of the true original lesion where lichen, eczema, or scabies have undergone such a change. The same causes,
as they explain the presence of ecthyma and rupia, guard against the need less assumption of a syphilitic taint. Poverty and dirt alike go hand in hand with scabies and prang°, but with the latter there is poverty of blood as well as of purse. The character of the food recently taken has often a definite relation to nrticaria. The habits of the individual and the condition of the digestive organs have a close relation both to acne and tubercle of the skin.
A life of dissipation affords grounds for the suspicion of syphilis ; and it is especially to be remarked that the diseases more nearly resembling it are chiefly of a cachectic character ; and in so far as such a condition is opposed to a life of gayety, does the suspicion become stronger, that the eruption is specific, if the idea of cachexia be not suggested by the aspect of the indi vidual, when no distinct avowal of primary symptoms can be obtained. Close confinement and impure air certainly prepare the way for the scrofulous forms of disease to which the more obstinate of the pustular eruptions have been with justice referred. A life in a warm climate is much more likely to give rise to tubercle of the skin than to lupus or acne.
The probability of contagion is another circumstance which sometimes influences the judgment. It must be remarked that, excluding syphilis, those eruptions only can be viewed as really contagious in which parasitic life is concerned ; at the same time there are sufficient facts to make us hesitate in asserting that others are not propagated in the same way. We can easily conceive that pustular matter reaching an abraded skin may give rise to sup puration there, and the disease once excited may continue, if the system be in a condition likely to insure its permanence : but the persons who seem to afford instances of this sort of contagion are usually exposed to the same influences, whatever they may be, that develop the disease ; and thus the spread of impetigo through a family or a school is no proof that it was communicated from one child to another.
The mistake more frequently made is that of assuming that impetigo must be either favus or scabies, as it happens to be on the scalp or on the limbs, because there seems to be good evidence of its having spread by contact.
Much attention must not be paid to the statement that the eruption itches or causes great irritation, as a guide to diagnosis. The susceptibility of the skin varies so remarkably in different individuals, and not less the moral courage to resist the inclination to alleviate the distress by scratching, which seems almost like an instinct provided for the purpose; and yet we all know how very greatly the itching is increased by the fresh irritation so produced. In one sense the information is of use, because where itching is complained of we may be sure that the inclination has been indulged, and that the appearance of the eruption is modified by it. No circumstance tends more to create varieties among the forms of skin diseases, and a great many of the anomalous examples may be referred to this cause.