from the preceding form in that to the tubercular alteration in the cutis there is further added growth of the papillæ and thickening of the epidermis. The last three forms described are also distinguished by their very chronic course and great poverty in tubercle bacilli. FIG. 201.-LUPUS OF THE SKIN in the stage of reaction after injection of Tuberculin. x 77. (Alum cochineal.) a, Epidermis with hypertrophy of the rete Malpighii; b, Elevation of the stratum corneum by pus (formation of pustule), which is to be regarded as indication of an inflammation set up in the lupus by the tuberculin (reaction); c, Enlarged papillæ; d, Epithelioid-celled tubercle containing giant cells. Syphilis occurs in the skin either as primary induration, or in the form of the so-called cutaneous syphilide. The former (Fig. 202) develops at the point of entrance of the syphilitic virus, and is characterised by a tolerably sharply circumscribed aggregation of lymphoid cells in the cutis (b), between which epithelioid elements and even isolated giant cells may sometimes also be present. Further, in the immediate vicinity of this infiltration the tissue of the cutis is somewhat richer in cells (c), and, above all, the small blood-vessels (d) show characteristic changes, their walls being densely infiltrated with small round cells (syphilitic vasculitis). The process may eventually subside again, the cellular infiltration undergoing a FIG. 202.-ULCERATING SYPHILITIC PRIMARY INDURATION OF THE PREPUCE. gradual transformation into connective tissue, or it may go on to ulceration (a), giving rise to the hard chancre (ulcus durum). The cutaneous syphilide only develops after the syphilitic virus has passed into the circulation, and may take a macular, papular, pustular, or gummatous form. CUTANEOUS SYPHILIDE 397 In the macular syphilide small red spots appear, whilst in the papular form little nodules (papules) develop from the spots, and on parts of the skin which are continually in a moist condition (anus, organs of generation, and the like) also attain a considerable superficial extent, being then named condylomata lata (Fig. 203). In both forms of cutaneous syphilide the histological changes consist FIG. 203.-CONDYLOMA LATUM. x 95. (Alum cochineal.) a, Stratum corneum; b, Rete Malpighii with thickened and elongated cones; e, Elongated papillæ; d, Smallcelled infiltration of the sub-papillary layer of the cutis. in small-celled infiltration of the walls and immediate neighbourhood of the blood-vessels, especially those in the papilla and the subpapillary stratum, but also those which twine round the hair-follicles, sebaceous and sweat glands, and arrectores pili muscles. Even the small blood-vessels in the deeper layers of the cutis and in the panniculus adiposus may be implicated in the changes described, whilst the endothelium of the diseased vessels may also take on growth. In addition to this the wall and immediate neighbourhood of the sebaceous glands and hair-follicles, as well as of the sweat-glands and their ducts, are found infiltrated with small round cells. In the papular form of syphilide the changes described are of greater extent and intensity than in the macular form. Not only do the small-celled infiltrations attain a higher degree in places, notably in the upper layers of the cutis and in the papillæ, and even, it may be, contain isolated giant cells, but round cells also penetrate into the rete Malpighii, whilst the superficial cells of the epidermis swell up and are cast off. In the condylomata the cones of the Malpighian layer may also increase in length and thickness (Fig. 203, b). If the cellular infiltration of the papules breaks down into pus, and at the same time the stratum corneum is raised by abundant accumulation of pus-corpuscles in the epidermis, and thus a pustule is formed, we have the pustular syphilide. Should the pustules become large the condition is spoken of as syphilitic pemphigus, and when the pus dries up into scabs, as rupia syphilitica. After the scabs have been shed little ulcers come to view, which can only heal by cicatrisation. The cellular infiltrations in the skin which lie at the basis of the macular and papular syphilides disappear only very gradually as the process heals, the round cells. in the first place changing to spindle cells. Vestiges of the infiltrations can be made out microscopically even several months after the process is apparently well, but these in most cases then consist solely of spindle cells, and occupy chiefly the walls of the blood-vessels. The gummatous form of syphilis of the skin is characterised by the development partly of small gummata in the cutis, partly of large ones in the subcutaneous connective tissue. Eventually they either subside again the larger after central caseation--or ulcerate. (For further particulars, see also p. 138.) A more or less abundant formation of pigment occurs in all cutaneous syphilides, the pigment, which takes the form of yellow or brown granules, or of a diffuse staining, being situated in round cells in the recent syphilides, but when the process has lasted longer, in the cells of the connective tissue. It is present in greatest abundance in the papillæ and in the adventitia of the blood-vessels. This pigment may still persist for a considerable length of time after the subsidence of the syphilide, or may even remain permanently; whilst in many instances, on the contrary, especially after papular syphilides, a deficiency of pigment (leucoderma syphiliticum) may be observed in the skin of certain localities (on the nape of the neck). On such spots, however, only the epidermis appears unpigmented, whereas numerous cells containing pigment are present in the cutis, especially in the papillæ at the periphery of the leucoderma. For lepra, glanders, rhinoscleroma, and actinomycosis of the skin, see pages 136, 140, 152, and 157. TUMOURS AND PARASITES 399 6. New-formations and Parasites. Of the more frequent newformations of the skin must be mentioned fibroma, lipoma, angioma, sarcoma, cystic tumours, carcinoma, and papilloma. Concerning the fibroma which starts from the cutaneous nerves (neuro-fibroma), see p. 83. When the last-named tumours are multiple, the cutaneous and subcutaneous connective tissue between them in many cases also shows a diffuse growth of the nature of elephantiasis (neuromatous elephantiasis). A similar diffuse growth may also accompany lymphangiomata and hæmatangiomata of the skin (lymphangiectatic, teleangiectatic, and cavernous elephantiasis). Most varieties of sarcoma are met with in the skin, where they occur either in solitary or multiple form, the latter especially in the case of melanotic sarcoma. Cutaneous carcinoma as regards its histological structure usually takes the form of a squamous-celled epithelioma, starting from the epidermis or from the epithelium of the sebaceous glands and hair-follicles; but in the case of carcinomata on the neck the epithelium of still-persisting relics of the visceral clefts may also form the starting-point. Lastly, there are cancers of the skin which arise from the epithelium of the sweatglands, and which then also approximate more nearly to an adenocarcinoma in their structure. The flat-celled epithelioma of the skin occurs in two forms, a flat and a deep-growing, according to the depth to which the cones of cancer cells penetrate, the first form being less malignant, but seldom giving rise to metastases, and usually forming shallow ulcerations, which may even cicatrise in the centre [rodent ulcer]. Places where the skin passes into a mucous membrane form the favourite seat of carcinoma; but, in addition, warts, scars, ulcers, and especially lupous ulcerations not uncommonly form the starting-point for cutaneous cancer. Regarding the other new-formations of the skin (lipomata, angiomata, cystic tumours, and papillomata), compare Part II., Chapters III. and IV.; for the skin diseases excited by the Hyphomyceta, see p. 162, and for Acarus scabiei and Acarus folliculorum, pp. 181 and 182. In Molluscum contagiosum should also be mentioned here. It forms nodules of lobular structure, consisting of agglomerations of epithelial cells which are separated from one another by fibrous septa. the centre of these agglomerations lie oval structures with a dull gloss, partly free, partly in the interior of horny epithelial cells. These are the so-called molluscum corpuscles, which are regarded by some as coccidia (p. 169), but by others as being merely degenerated epithelial cells. The adherents of the first view believe molluscum contagiosum to be an epithelial growth excited by coccidia, and |