Treatment usually consists in softening the skin by friction with soap and warm water, followed by a warm bath, and then applying some substance to kill the mites. Stiles gives the following directions, modified from Bourguignon's, as "a rather radical guide, to be modified according to facilities and according to the delicacy of the skin or condition of the patient": 1. The patient, stripped naked, is energetically rubbed all over (except the head) for twenty minutes, with green soap and warm water. 2. He is then placed in a warm bath for thirty minutes, during which time the rubbing is continued. 3. The parasiticide is next rubbed in for twenty minutes and is allowed to remain on the body for four or five hours; in the meantime the patient's clothes are sterilized, to kill the eggs or mites attached to them. 4. A final bath is taken to remove the parasiticide. The parasiticide usually relied on is the officinal sulphur ointment of the United States pharmacopœia. When infestation is severe it is necessary to repeat treatment after three or four days in order to kill mites which have hatched from the eggs. The above treatment is too severe for some individuals and may, of itself, produce a troublesome dermatitis. We have seen cases where the treatment was persisted in and aggravated the condition because it was supposed to be due to the parasite. For delicate-skinned patients the use of balsam of Peru is very satisfactory, and usually causes no irritation whatever. Of course, sources of reinfection should be carefully guarded against. _Sarcoptes scabiei crustosæ_, which is a distinct variety, if not species, of the human itch mite, is the cause of so-called Norwegian itch. This disease is very contagious, and is much more resistant than the ordinary scabies. Unlike the latter, it may occur on the face and scalp. _Sarcoptes scabiei_ not only attacks man but also occurs on a large number of mammals. Many species, based on choice of host, and minute differences in size and secondary characters, have been established, but most students of the subject relegate these to varietal rank. Many of them readily attack man, but they have become sufficiently adapted to their normal host so that they are usually less persistent on man.