PSORIASIS. 



485 



into a crust, while upon its edges a border of bullse forms, the contents 

 of which dry up like those of the first one. Thus, the peripheral part 

 of the scab is flatter than the older portion ; the scabs of rupia are 

 thick in the middle and flat at the edges, bearing some resemblance 

 to oyster-shells. In most cases, but not in all, rupia is a symptom of 

 constitutional syphilis. The causes of non-syphilitic rupia are un- 

 known. Like ecthyma, it occurs most commonly in broken-down and 

 cachectic subjects, 



SYMPTOMS AND COURSE. The usual seat of non-syphilitic rupia is 

 upon the extremities. The blebs are isolated, and have a reddened 

 base. They are not tightly filled, and their contents at first are limpid, 

 afterward yellow or reddish. The scabs which form are of a dark 

 color, and, after lasting some time, assume the shape described above. 

 According as the thickness of the scabs is slight or considerable, they 

 are distinguished into rupia simplex and rupia prominens. Removal 

 of the scab exposes either an excoriation, or else a deep ulcer, over 

 which a new scab soon forms. Sometimes the base of the bleb not 

 only ulcerates, but becomes gangrenous (rupia escharotica s. gan- 

 grenosd). In such case the contents of the blebs are discolored or 

 blackish. Beneath them, or beneath the scab, we find the corium de- 

 stroyed and converted into a foul ulcer, covered with debris of the 

 tissue, and indisposed to heal. Rupia simplex and prominens usually 

 recover, leaving behind them a shallow scar, which is often stained 

 with pigment ; while rupia gangrenosa may cause death from exhaus- 

 tion, or may accelerate the end of the already exhausted patient. 



TREATMENT. Our principal task in the treatment of rupia consists 

 in combating the constitutional vice upon which it depends. If we 

 succeed in this, young epidermis soon forms beneath the scabs, and 

 the ulcers heal. But if we do not succeed in improving the constitu- 

 tion, local treatment will generally be found useless also. Besides 

 the constitutional remedies, the scabs may be softened by poulticing. 

 The ulcers which remain require stimulating applications, such as re- 

 peated touching with lunar caustic. 



CHAPTER XII. 



PSORIASIS CHRONIC DERMATITIS WITH INFILTRATION OF THE CORIUM, 



AND ABNORMAL GROWTH OF EPIDERMIS. 



ETIOLOGY. In psoriasis, the effusion which forms upon the sur- 

 face of the corium is insufficient to elevate the epidermis into vesicles. 

 On the contrary, this form of dermatitis, which is always chronic, con- 

 sists merely of a hyperaemia and infiltration of the skin, capable of 



