512 



THE POPULAR SCIENCE MONTHLY. 



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but the mode of transmission has been a puzzle, it being observccl 

 that among doctors and hospital attendants infection was compara- 

 tively rare. This is explained by the nocturnal habits of the mite — 

 or, if not truly nocturnal, its activity is promoted by a certain degree 



of warmth, so that it lies dormant 

 during the day, when the body is 

 cool, to sally forth in searcli of 

 new fields when stimulated by 

 the genial warmth of the bed. 

 This explains also why the itch- 

 ing is most violent at night. The 

 fMfj mode of getting rid of the para- 

 site IS obvious ; we have only to 

 kill it; and, fortunately, the 

 means is cheap, easily applied, 

 and perfectly eflectual : sulpliur, 

 which seems to be a deadly bane, 

 to all insects, in whatever shape 

 it can be given. It is only ne- 

 cessary to expose the insect to its 

 influence, and it surely dies. 



One curious point regarding 

 these mites is, how they produce 

 the physiological effects that 

 characterize their attacks. Their 

 incessant gnawings and nibblings 

 are undoubtedly sufficient to 

 cause great irritation ; but there 

 are the different symptoms in- 

 duced by different species — scur- 

 fy, inflamed surfaces, coarse, lep- 

 rous crusts, deep ulcers, etc. ; can 

 these be accounted for by de- 

 grees of mechanical irritation, or 

 are they possibly the result of some special poisonous virus ? The itch- 

 mite is found on the lion, dog, sheep, ox, horse, pig, and other animals, 

 as well as on man. There are several other species, as the S, scahiei- 

 crustosce, or Norwegian itch-mite, most common in Norway, but not 

 wholly confined to that country. The mite is much like the common 

 species, but smaller and darker. The malady is similar to that of the 

 common itch, though all the symptoms are intensified, the tubercles 

 and crusts growing enormously. It yields, however, to cleanliness 

 and the sulphur treatment. S. cati infests the domestic cat, the points 

 of attack being the base of the nose, the lips, the ears, and the eyes, 

 but spreading in all directions ; the animal is reduced to a pitiable 

 condition, being literally devoured alive by the parasites, if not de- 



Fig. 12.— Burrow of Itch-Insect (Sarcoptes sca- 

 We?').— Female depositing eggs. The eggs lying 

 next to the insect consist partly of an homoge- 

 neous, partly of a granular mass : in those dis- 

 tant from the insect embryos are already de- 

 veloped, and at the entrance of the furrow a 

 moving acarus is seen. 



