so-called mange in cats, dogs, horses, and cows is often only scabies. Transient association with a patient suffering from scabies, as, for instance, in medical examination, will not necessarily give rise to infection; but this frequently occurs among those who sleep together. Also cheap lodging-houses, in which the, bed-linen is changed but seldom, constitute a frequent source for infection.

The itch-parasite is just visible to the naked eye as a small, grayish-white dot. Its form suggests that of a tortoise (Figs. 36, 37, 38). The males, whose number is considerably less than that of the females, are smaller than the latter, and can be readily recognized from the bifurcated penis upon their ventral aspect. In addition, they possess not only upon the two forefeet, but also upon the hind feet, a sucker (ambulacrum), while the two pair of hind feet of the female possess bristles. After fertilization the female bores its way into the epidermis, and forms the itch-groove, where it deposits its ova, and from these the larva develop in from six to twelve days. The larva at first possesses but three pair of feet. It exfoliates three times, and emerges from the first exfoliation with four pair of feet. The female parent deposits on an average two eggs daily, and after a single fertilization deposits as many as fifty eggs altogether.

Symptoms and Diagnosis. In the clinical picture of scabies two sets of symptoms must be differentiated, namely, the alterations to which the itch-mite itself gives rise, and, besides, the changes in the skin resulting from the itching and the scratching. The latter are, without doubt, the more extensive. The changes of the first variety are confined essentially to the boring of an itch-groove in the epidermis on the part of the fertilized and pregnant female acarus. The males, apparently, remain in depressions in the skin close to the orifices of the itch-grooves. The length of such a groove occasionally reaches 5 cm., although generally it is from 0.5 to 1 cm. Each female strives to bore more

and more deeply, in order to obtain new, juicy, nutritive material. After the act of parturition has been completed the female parent dies at the deepest portion of the groove. An itch-groove can be readily recognized from its sharp limitation, inasmuch as it acquires a black appearance from the presence of dirt. Its course is generally tortuous. If it be punctured with a needle, the parasite can be readily extracted. Frequently, the entire itch-groove, together with its contents, can readily be removed from the epidermis by means of scissors, and be examined with the microscope, particularly if it be cleared by the addition of potassium hydroxid (p. 214, Fig. 39). Often the patient has scratched open

such grooves. The itch-mite especially prefers to make its groove in thin and comparatively juicy epidermis, and the burrows are found most frequently and in greatest number between the fingers, upon the flexor aspect of the wrist, in the axillary region, on the nipple, at the umbilicus, on the genitalia, over the trochanters, in the popliteal spaces, and in the gluteal region, as well as on the inner border of the foot. The face generally remains free, although in infants it is often involved if infection is acquired by application to the breast.

Papules, vesicles, and even pustules generally develop in the immediate vicinity of the grooves. The intolerable itching to which the itch-mites give rise, particularly from the heat of the bed, induces scratching on the part of the patient, and in this way a secondary eczema results, consisting of papules, vesicles, pustules, and crusts. Should crusts become superimposed upon one another, particularly upon the face and upon the scalp, and should, in addition, the nails become thickened and cracked, the condition has been designated Norwegian scabies; but this occurs only in neglected and long-standing cases. Enlargement of adjacent lymphatic glands-bubocs-occurs as a complication, and occasionally suppuration may even take place. If patients with scabies are attacked by a disease attended with high fever, the itching of the skin ceases during the persistence of the fever, because the female parent dies as a result of the elevated temperature, but the itching recurs after defervescence as soon as new acari have developed from the ova.

Prognosis. The prognosis of scabies is good, for the disorder can be cured with certainty within a short time.

Treatment.-Among the prophylactic measures frequent change of body-linen and bed-linen and treatment of mange in animals may be mentioned. The simplest remedy for the cure of scabies consists in a combination of balsam of copaiba and liquid. styrax, with which the skin should be rubbed morning and evening for two days in succession, in order to destroy the acari and their ova:

R Balsam of copaiba,

Liquid styrax,

For inunction twice daily.

50.0 (1) fluidounces).—M.

On the third day the patient should take a hot bath, and wash the skin with green soap. At the same time clean body-linen and clothing are put on, and the bed-linen is changed. The soiled linen should be thoroughly boiled and washed. The clothing should, if possible, be disinfected by exposure to the action of live steam, thus in a sterilizing apparatus. Often the eczema resulting from the scabies will require treatment in the usual manner for some time.

Among many other remedies for scabies it will suffice to mention further inunctions of petroleum, sulphur, lime, tar, or soap. In hospitals the solution of Vlemingkr is much employed:

Excessive friction of the skin should be avoided, as albuminuria and acute nephritis may result therefrom.

ACARUS FOLLICULORUM.

The acarus of the hair-follicles is a harmless parasite for human beings, finding lodgment within the sebaceous follicles, as many

FIG. 10 -Acarus folliculorum after Landois).

as twenty being present in a single follicle. It is especially common upon the bald head in the aged. If sebaceous matter be expressed with the finger-nails, and be smeared upon a slide with a drop of oil, the parasite can be readily recognized from its slender form and its four pair of feet (Fig. 40).

PEDICULI (LICE).

Three varieties of pediculi occur in human beings, namely, the head-louse-Pediculus capitis, the crab-louse-pediculus or Phthirius pubis, and the clothing-lousePediculus restimentorum. Among these the clothing-louse is the largest, the crab-louse the smallest.

HEAD-LOUSE (PEDICULUS CAPITIS).

Head-lice are encountered only upon the scalp. The females, which always exceed the males in number, and are larger than the latter, attain a length of 2 mm. With their curved, six-hooked feet (p. 218, Figs. 42, 43) the lice are well able to climb upon the hairs. The fertilized female in this process deposits its ova or nits upon the hair, and these are readily recognizable as gray dots. On microscopic examination, the ova are found to be attached to the hairs by means of a chitinous sheath (p. 217, Fig. 41). The fertility of the pediculi is remarkable, as a single female parasite may deposit as many as 5000 ova within a period of six weeks. Within from