Page:The American Cyclopædia (1879) Volume VI.djvu/707

 EPIZOA 695 other form the shape is nearly the same, but the whole animal is smaller, and has but three pairs of legs ; this is undoubtedly immature. Still a third presents itself with a body like that first described, but with a hinder extremity no lon- ger than the body, and of a conical form, dis- playing transverse chitinous rings. It seems much more plausible to consider this the male, than to suppose that the tails of the former varieties drop oil' or shorten. No definite in- ternal structure has yet been made out. "Wedl and some other observers think they have made out within the body of the female, and in the field, immature forms without extremi- ties; and if this be true, they are viviparous. They are found generally in the hair follicles of the nose of thick and fat-skinned persons, but may yet be met with on the breast or back, or wherever comedones occur, of which, when present in numbers, they may be the cause, although generally they occasion no trouble. They are usually found with their hinder ex- tremity next the surface, and either close to the hair, or in the canals of the fat glands, upon the secretions of which they live. Their oc- currence is very general, and to find them, we have only to squeeze the foliicles on the sides of the nose between the finger nails, and to add to their contents beneath the microscope a drop of oil, by which the sebaceous matter is rendered clear. In the dead body they will be found much more deeply seated, as if they had sought warmth by penetrating toward the interior as the surface became cold. The aca- rus or sarcoptes scabiei, or itch insect, will be fully considered in the article ITCH. Still other forms of acari or sarcoptes are sometimes met with on man, transferred to him from the beasts on which they live. Their occurrence is purely accidental, and they are never known reproduce in such situations. The eruption ley cause may be of long continuance, but ily because fresh infection takes place by continued contact with the animals affected. The sarcoptes of the various domestic quadru- peds produce upon them the disease known as mange, and are specifically different. The mite of the cat and lion, however, resembles and is probably identical with that of man ; so that it is a question whether these creatures got their itch first from man or vice versa. The parasite of the horse is large enough to be visi- ble to the naked eye, and its mode of burrow- ing and of reproduction is nearly the same as that of the sarcoptes hominis. It produces a dry scaly appearance of the skin, which is some- times called "scratches." The cheese and dried-fruit mites may likewise live for a short time on the skin, but cause nothing more than a passing irritation. The family of ixodes, or ticks, is also a great plague to man and beast. They live on moss and dry foliage, on sunny hillsides, and in groves and thickets, and never fail to attack grazing cattle and passers by. They bore into the skin with their sharp pro- boscis armed with horny barbs, and remain hanging till the body, at first minute and flat, becomes swollen with blood, even to the size of a bean. To tear them away is impossible on account of their recurved barbs, and great cau- tion and patience are necessary ; for if violence is used, the head remains behind, and causes in- flammation, which may last for months. Gen- erally long and gentle rubbing with some es- sential oil will make them quit their hold vol- untarily. They lay a vast number of eggs, and their multiplication upon oxen and horses is sometimes so great that the ani- mals die of exhaus- tion. The gama- sida, beetle lice, are other mites pa- rasitic on birds, reptiles, and in- sects, and both land and water beetles are often found cov- ered with them. The dermanyssus avium abounds in Bird Mite (Dermanyssus avium). great quantities in bird cages and hen houses, and lives upon the blood of their inhabitants. Numerous cases are on record of their presence in great num- bers on persons who frequent such locali- ties, penetrating and living beneath the epider- mis. They produce the disease occasionally met with among the wretched and filthy sick of the poor, called acariasis. Colonies of mice are often infested with similar parasites. An- other mite similar to the ixodes is the leptus autumnalis of Europe, which, living in grass or grain or upon fruit bushes, gets upon the reapers and passers by, and causes pustules and sores. It is red, whence the name of the disease, rou- get. A similar pa- rasite is the lete rouge of Marti- nique, which often renders necessary amputation of the sufferer's limbs. III. Insecta. In this division we shall consider the parasitic insects of animals in order commencing with those of the mam- malia. The human body serves as a residence for several of these, the best known and most numerous of which are the pediculidce, or lice, which belong to the apterous ametabola, or wingless insects without metamorphosis. Four are peculiar to man : Pediculm capitis, P. vestimenti, P. tabescentium, and pfitJii- rius pubis or inguinalis. The head louse is grayish white, and it is supposed to adapt itself to the color of the hair of its host. The males are smaller and less numerous than the Ked Mite (Leptus autumnalis).