Local Dermal Inflammations

Under the head of local dermal inflammations we include those diseases which partake essentially of the nature of local diseases, and are characterized by inflammation, as the primary and the essential phenomenon. By inflammation we understand not merely hyperaemia, with engorgements of the affected parts by blood, so that the parts are swollen and red and hot, not only hyperaemia, with stasis in the vessels and serous effusion in addition; but also an increased activity in the tissues themselves outside the vessels, and the formation of new products, or "inflammatory exudation," to use a commonly employed term. The character and source of these new products are important items in this matter of inflammation. As regards the character of the new product, its typical features, and ultimate destination in marked cases are those of pus. Pus, in fact, is the highest grade of inflammatory products, but pus is not necessarily formed, and it is held that the new products may give rise to the production of a tissue-like connective tissue. Pus is derived from two sources - namely, from white blood cells, and also from connective tissue corpuscles. There are three leading changes observed in inflammatory exudation - resolution, organization and suppuration. The local inflammations we are about to consider are generally characterized by hyperaemia and the presence of inflammatory infiltration. They are the erythemata; eczema, or catarrhal inflammation; that form which commences as a serous catarrh of the papillary layer, and is followed by the outpouring of seropurulent discharge, as in catarrh of the mucous membrane; plastic or papular inflammation, in which the inflammation is characterized as much by the absence of serous as by the deposit of fibrinous exudation; suppurative inflammation; and lastly, hyperaemia, accompanied by excessive formation' of epithelial and certain cell growths in the papillary layer, conveniently termed squamous inflammation, as in psoriasis.


Two of these groups or classes, might be separated from inflammation perhaps, and dealt with as hyperaemias solely, and these are the first and the last of the above named. In the former there is hyperaemia and serous exudation, as in erythema; but what is the important thing to notice in relation to the point under discussion, there is no cell proliferation or cell infiltration in the tissues. If the hyperaemia is persistent then there follows in due course hypertrophy. To avoid, however, making another group in classification I have grouped the erythematous diseases under the head of local inflammations. With regard to "squamous inflammation," there is here only hyperaemia and hyperplasia or hypertrophy, and no actual inflamma­tory infiltration. Psoriasis, the type of the class, is on the borderland only of inflammation; but we will group it under inflammations for the present at all events.


The reader will very naturally want to be told wherein lies the difference between hypertrophy and hyperplasia following hyperaemia, on the one hand; and the changes that occur in the skin in zymotic diseases, and those that are observed in lupus, syphilis, and leprosy on the other hand; and what are the differences that lead dermatologists to make the special class of diseases to be dealt with in this chapter. In the first place, with regard to the local changes in the zymotic diseases - as small-pox and typhoid  - these are only parts of a general malady, and could not be regarded in a group characterized essentially by peculiarities of local change. From an etiological point of view it would be impossible to do so. Then, in regard to lupus, syphilis, etc., there are certain anatomical characters and behaviors about the growths, which, no less than peculiar concomitants of associated constitutional states and the like, that mark them as belonging to a special class of neoplasmata or heterologous new formations. In regard to the distinction to be drawn between hyperplasia consequent on inflammation, and hypertrophy, the latter is much slower, even if the etiology be left out of view; there is in the one the escaped blood cells developing into the new tissue, and in the other the increased supply of blood and transuded serosity. But the two have certain analogies, and it is difficult if not impossible to draw a line between hypertrophy and inflammation. But further, it may be said - and this applies to tumors and special neoplasms, as lupus and syphilis - whilst the inflammatory infiltration is caused by some irritant, the tumor or heteroplastic neo­plasm arises spontaneously, or from a specific cause acting generally and modifying nutrition. There is with inflam­mation the accompanying heat, redness, pain, and swell­ing, and these "signs" acutely developed; there is less tendency to spontaneous cure1 with tumors; and lastly, the inflammatory exudations directly tend to the formation of pus.