510 DISEASES OF THE SKIN. 



CHAPTER XXI. 



PITYRIASIS VERSICOLOR. 



ETIOLOGY. Eichstedt^ of Greifswald, was the first to demonstrate 

 that pityriasis versicolor, which used to be ascribed to a derangement 

 of the hepatic function, is really dependent upon the growth of fungi 

 in the epidermis. In this affection, the filaments are more numerous 

 than the spores. Its very common occurrence among patients with 

 pulmonary disease shows that the skin of such individuals often presents 

 favorable conditions for the implantation and growth of the parasite. 

 Pityriasis versicolor is a very common affection, and often appears upon 

 perfectly healthy persons. 



SYMPTOMS AND COURSE. The most common seat of pityriasis 

 versicolor is upon the neck, back, chest, and arms ; but I have never 

 seen it spread from the neck to the face. In recent cases, small, round, 

 yellow spots, which readily peel off, are found upon the affected skin ; 

 in cases of longer standing, the spots are larger or have coalesced, 

 forming irregular patches, which often extend over a large portion of 

 the skin. The yellow spots can easily be scratched off by the finger- 

 nail, and by this means, as well as by their ordinary situation, and, 

 still better, by the discovery of the parasite in them, they may be dis- 

 tinguished from chloasma uterinum and from freckles. Pityriasis versi- 

 color often occasions a slight itching. During summer it generally 

 improves somewhat, probably because the perspiration is freer ; but it 

 scarcely ever disappears unless judiciously treated. 



TREATMENT. I used formerly to treat pityriasis versicolor with 

 a mixture of carbonate of potash 3 vj, liquor hydrarg. nitric, oxydul. 

 3 iij, and aquae rosarum | vj, which must be well shaken, that the sub- 

 oxide of mercury may not remain at the bottom of the bottle. Under 

 this application, made morning and evening, pityriasis versicolor has 

 nearly always disappeared in a week or ten days. Recently I have 

 found that the same object may be attained with equal facility, by in- 

 unction of green soap twice a day. 



CHAPTER XX11. 



SCABIES ITCH. 



ETIOLOGY. The itch is an inflammation of the skin characterized 

 by the formation of nodules, vesicles, and pustules, and caused by the 

 presence of an animal parasite, the itch-mite, acarus scdbiei, or sar- 

 coptes hominis. The parasite is about J'" in length, and has a breadth 



