LOUSE, Pedicutus, a genus of insects, the type of a very numerous family, which forms the order parasita or anoplura. The body is flattened, almost transparent; the segments both of the thorax and abdomen very distinct; the mouth is small and tubular, inclosing a sucker; there are no wings; the legs are short, and are terminated by a claw adapted for taking hold of hairs or feathers. The eyes are simple, one or two on each side of the head. All the species are small, and live narasitierdly on human beings, terrestrial mammalia, and birds. They deposit their eags on hairs or feathers, to which they attach them by a glutinous substance; and they multiply with astonishing rapidity. The young cast their skin several times before they reach their maturity, which in the best known species is said to be about eighteen days after they are hatched, bnt, from the first, they are very shnilar to their parents. Animals of different kinds are infested by different species of louse peculiar to them; those which are found on birds exhibit ing characters considerably different from those of man and mammals. The sante species is rarely found on different species of animals, unless very nearly allied; but some animals have more than one of these parasites. Three infest the human race: one confined to the head, the COMMON LOUSE (P. capitis); another, the BODY LOUSE (P. vestimenti 8. corporis), very similar to it, but of a larger size; a third. the CitAn Lousu (phthirius pubis), sometimes found in the eyebrows, but more frequently in the pubic region, and chiefly in persons of licentious habits; having the body broader, and other characters considerably different from the other two. The common or head louse is a very common parasite. The symptoms which the bites of these insects produce are a troublesome itching, and a more or less apparent eruption upon the scalp, the eruption being usually- accompanied by small incrustations of blood produced by scratching off the epidermis. On examining the head, in addition to the insects, numerous eggs called nits are found, which are of a pyriform shape, and adhere firmly to the hairs. In six days the young escape from the egg; at the age of eighteen days these are again ready to lay eggs; and the,female lays 50 eggs in all; so that the rapid augmentation of these insects is easily accounted for. When only a few lice are present, they may be
removed by careful combing, or may be killed by the free application of oil or poma tum to the head; but when they are abundant, the scalp should be sprinkled with the Persian insect-powder (pyrethrum caucaseum), which, according to Ktichenmeister, soon kills them, or rubbed with white precipitate ointment, which is the most common remedy in this country.
The body louse causes most irritation on those parts of the skin which. correspond with the folds and seams of the clothing about the neck and round the waist where the clothes are fastened to the body, The irritation is of the same character as that caused by the preceding species, and the treatnient is similar. It is said that the clothes may be purified by burying them in hay for several weeks, but the safer plan is to destroy them. The irritation caused by the crab louse is greater than that caused by the other species. It may be destroyed by one or two applications of an essential oil (oil of rose mary for example), or of white precipitate ointment.
Whether the pediculus talrescentium, or louse occurring in the lousy disease, is or is not a distinct species, is still an open question. Indeed, the fabulous element enters so largely into most of the recorded cases of this disease--as, for example, when Arnatus Lusitanus relates that two slaves were incessantly employed in conveying to the sea in baskets the lice which appeared on the body of their master—that the question is of comparatively little importance.
. An interesting question has been raised with regard to the lice infesting human beings, it being alleged, by those who desire to establish the essential diversity of cer tain races, and particularly by Americans anxious to make out the widest possible dif ference between the European race and negroes, that the lice found on different races are specifically different. The subject has been examined with great care by Mr. Murray of Copland, and with evident impartiality; the result being, as appears from his paper in the Transactions of tke Royal Society of EdinWrglt, that the differences among these parasites are like those among the races of men themselves, easily observed, but not certainly specific.