PEDICULOSIS CAPITIS

Synonyms: Pediculosis capillitii; Phthiriasis capitis; Head-lousiness.

Three varieties of lice infest man—Pediculus capitis, Pediculus corporis and Pediculus pubis. Pediculus capitis, the head louse, dwells exclusively on the scalp. It is 1 to 3 mm. long and about half as broad. The color is a translucent gray except along the lateral borders, which are almost black. Immediately after feeding, the animal gets a red tinge from the ingested blood. Its thorax is relatively narrow and provided on either side with three strong, hairy, jointed legs, each of which ends in a sharply curved hooklet. The flat, oval abdomen is composed of seven segments clearly defined by deep lateral notches. The eggs or nits are minute, gray or light yellow, shiny, pear-shaped bodies, visible to the naked eye. Each is firmly glued to the side of a hair with its larger end projecting away from the axis and toward the distal extremity of the shaft. The nits are easily found in every case of pediculosis capitis, though even when the nits are fairly numerous a diligent search may be required to locate a single pediculus. The ova are sometimes present in enormous numbers, several on a single hair. As a rule the eggs are deposited near the mouth of the hair follicle, thus the nit farthest from the scalp is the oldest. The hair grows about three-fourths inch a month; the duration of a recent case of pediculosis capitis can be estimated roughly from the distance of the nits from the scalp. The eggs hatch in about a week and the parasites reach maturity in less than three weeks. Each female is capable of depositing at least fifty eggs. A louse extracts nourishment through the skin by inserting its

haustellum into a follicle and inflicting a minute wound from which the parasite sucks up a small quantity of blood. A punctiform hemorrhage usually remains to mark the site. The feeding and movements of the insects excite a moderate pruritus. The impetiginous and eczematous lesions commonly present in any pronounced case are, to a large degree, the result of scratching. Often on the neck near the hair line, occasionally on the ears and, in children, even on the face and shoulders, are to be found papules, pustules and excoriations. On the scalp in addition, there may be large, thick, yellowish-brown crusts covering purulent, granulating areas. The cervical lymph glands are frequently enlarged. It is only in extremely neglected cases that the hair sometimes becomes glued by exudations and matted into the unravelable felt-like mass known as plica polonica. **DIAGNOSIS:** In a superficial examination *seborrhoeic scales* might be mistaken for nits, but the former frequently entirely surround the hair and are always easily brushed away. A nit compressed between the thumb nails bursts with a clearly audible crackle. **TREATMENT:** The destruction of the lice is accomplished by soaking the hair overnight in a 10 per cent tincture of staphisagria, or in crude petroleum. To lessen its inflammability the petroleum may be mixed with an equal quantity of olive oil. The next morning the hair should be washed with soap and water, then moistened with dilute acetic acid and combed with a fine-toothed comb to remove the nits. The acetic acid softens the glue which fastens the nits to the hairs. The skin lesions usually heal rapidly when the source of irritation is removed.

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