ACAEUS SCAB1EI. 25 



the inner surfaces of the limbs, the entrance to the ^axillae, the 

 abdomen, the anal cleft, the scrotum, the penis, the nipples, the 

 cavity of hair-follicles, &c. When they have got under the epi- 

 dermis, the boring goes on more rapidly. The hinder part of 

 the animals sinks, and the mite penetrates in an obliquely 

 pierced passage towards the cutis. The knowledge of this 

 direction is of importance for the discovery of the mites in their 

 galleries. 



Various methods have been employed for the detection of the 

 mites. The best is that of Eichstadt and Hebra, which Gudden 

 has only modified in one point. To examine places in the skin 

 on which points, papillae, vesicles, or passages occur, the skin is 

 raised, if possible, into a fold, and the epidermis, with the super- 

 ficial layer of the cutis, is removed from it, according to Eichstadt 

 and Hebra, with a pair of scissors, but to suit the surface; and, 

 according to Gudden, with the rapid stroke of a fine sharp 

 knife, which certainly gives some pain, but not so much as the 

 removal with the scissors, and does not leave such a bad wound. 

 Eichstadt rubbed green soap into the spot selected for inci- 

 sion on the previous day, in order to produce a slight inflamma- 

 tion and exudation, which somewhat elevate the gallery and 

 facilitate the excision. The fragment of skin thus removed is 

 carefully spread, with the inner surface upwards, upon a glass 

 plate, and the preparation is allowed to dry slowly, but not to 

 become brittle; it is then turned over, laid in concentrated 

 mastic varnish, and after getting rid, as far as possible, of inju- 

 rious air-vesicles by gentle pressure, or, when this is of no use, 

 by leaving the preparation for twenty-four hours in the varnish, 

 it is put under the microscope. The outlines of the gallery are 

 certainly thus rendered almost transparent and extremely deli- 

 cate, but particularly easy to recognise where they contain a mite, 

 or a few balls of excrement. In short, in this way we contrive 

 to observe the entire natural history of the mite at one glance. 

 Still more easy, and in ordinary cases sufficient for the diagnosis, 

 is the method already described by Aldrovandi, Nyander, Bate- 

 man, and Wichrnann, and again introduced into science by 

 Henucci, who learnt it from the Corsican women. With the 

 naked eye or with the lens (Schinzinger), we examine a large pas- 

 sage, and pierce it carefully from the side at the end, where a 

 whitish point shines through, with a cataract needle, a lancet, 

 or a common needle, remove the covering from the passage, and 



