26 ANIMAL PARASITES. 



thus get below the mite, which is exposed, and lift this out. 

 Many have acquired great expertness in this process. 



The males can only be found with the lens. According to 

 Worms they are always in the vicinity of the galleries, and 

 shine, as brown points, through the skin, which only exhibits 

 slight traces of reaction. Here we must choose the removal of 

 such points with the knife. 



The young mites are usually found only in fresh vesicles, as 

 they readily emigrate ; but mites engaged in the change of skin 

 often occur in the papillae and vesicles which have already 

 attained a further development. If we wish to search for these 

 little pale creatures, great care is required, and we must have 

 good magnifying glasses attached to the eyes. The object is 

 better attained in this case by the removal of the vesicle, espe- 

 cially if we examine the vesicles starting up after a thorough 

 washing with soap (Eichstadt), or, what is better, with oil of tur- 

 pentine. The mites remain dead on the spot where they lie, 

 and the reaction subsequently produced shows their position. In 

 vesicles (that is to say, the anterior extremities or heads of the 

 galleries) or in true pustules, we either find no mites at all, or 

 only dead ones. 



The course of the disease, from the moment of the immigra- 

 tion of the mite into the skin up to its height, has certainly 

 been best elucidated by Gudden, by his inoculation experi- 

 ments. 



If a female, a male, or a young animal, gets upon the warm, 

 uninfected skin, the little animals, and especially the males, run 

 quickly about, according to Worms, passing over a space of two 

 centimetres in a minute, then stop, turn round, run further, and 

 either bite in immediately, or quit the spot and commence afresh 

 in another place. These manoeuvres may be traced with the 

 naked eye or with the lens, when a specimen of one of the above- 

 mentioned degrees of development is placed upon the outer 

 lateral surface of the hand, of which the mites are particularly 

 fond, and where they may be easily isolated. If the animals 

 run away from it they are brought back with the needle, or if 

 they will not bite in at all, they are removed altogether. The 

 mites bore, as already stated, perpendicularly into the epi- 

 dermis, and when they have pierced this layer, they penetrate 

 obliquely into the cutis, never below this, as under the lowest 

 stratum of the epidermis, they find their principal food. If they 



