SCABIES. 



511 



Df about $'", and is recognizable as a round white body to the naked 

 eye. Under a sufficient magnifying power, it is seen somewhat to re- 

 semble a tortoise in shape ; its convex back is marked with curved 

 parallel transverse stripes, and is armed with spines of varying length. 

 The young insect has six, the adult eight, articulated feet, the anterior 

 pair of which are provided with suckers. In the female, two pah* of 

 the hindmost of the feet terminate in long bristles ; in the male, only 

 the first of them has bristles, while the posterior pair are also provided 

 with suckers. The head of the mite, which is armed with two horny 

 jaws, separated by a cleft, projects from between the anterior pair of 

 legs. The male insect is smaller than the female, and much less nu- 

 merous ; it is provided with a penis shaped like a horse-shoe ; the fe- 

 male, when pregnant, embeds itself between the lamellae of the epi- 

 dermis, and forms a burrow which is often several lines in length, and 

 sometimes an inch or more. These passages contain empty shells of 

 the mites, together with then* blackish faeces, and then* eggs in every 

 stage of development. The burrows dug by the males are shorter, 

 and therefore more difficult to find. The eggs seem to mature in 

 about eight days. The young mites, after escaping from their shells, 

 abandon the gallery of their mother, and burrow for themselves in the 

 vicinity. After casting their skin repeatedly (twice at least), and ac- 

 quiring an additional pair of legs with the first moulting, they come 

 out of their holes and pair generally during the night, when the skin 

 is warm, in the bed. Sometimes the male insect visits the female in 

 her burrow. If a fecundated female be transferred from the skin of 

 one individual to another, the latter also becomes infected by itch. 

 As there is no opening in the galleries, and as those in which the 

 pregnant females lodge are stopped up by the eggs and fecal masses, 

 it may be assumed that the female only comes to the surface when 

 her burrow is scratched open. Sleeping with a person afflicted with 

 itch is, therefore, an especially dangerous procedure, although a very 

 brief pressure of the hand will suffice to transfer a mite scratched out 

 of her abode. It is not known how long the insect is capable of liv- 

 ing after it has been removed from its natural habitation and feeding- 

 ground ; but it seems that those which get into the clothing and linen 

 soon die. One of Hebrews discoveries proves the truth of this most 

 strikingly, and indeed better than the most minute observation of a 

 few captured mites. In Vienna, where fifteen hundred itch-patients 

 are treated annually, the number of relapses does not amount to one 

 per cent., although their linen, and other clothing, is not steamed nor 

 baked in the louse-oven, nor subjected to any other particular process, 

 in order to kill the itch-mite and its eggs. We are indebted to Mch- 

 stedt, Fftrsteriberg, Gudden, and others, for our more intimate acquaint- 



