| FIG. 112.—Trichocephalus dispar; a, Female; b, male (natural size) (Heller). |
The number present is usually small. The worms themselves are rarely found in the feces. The ova, which are not often abundant, are easily recognized. They are brown, ovoid in shape, about 50 µ long, and have a button-like projection at each end ([Fig. 101]).
III. ARTHROPODA
Most of these are external parasites, and the reader is referred to the standard works upon diseases of the skin for descriptions. The itch-mite (Acarus scabiei) and the louse (Pediculus capitis, corporis, vel pubis) are the more common members of the group.
A number of flies may deposit their ova in wounds or in such of the body cavities as they can reach, and the resulting maggots may cause intense irritation. Ova may be swallowed with the food and the maggots appear in the feces. Probably most important is the "screw worm," the larva of Compsomyia macellaria, infection with which is not rare in some parts of the United States. The ova are most commonly deposited in the nasal passages, and the larvæ, which may be present in great numbers, burrow through the soft parts, cartilage, and even bone, always with serious and often with fatal results.
CHAPTER VII
MISCELLANEOUS EXAMINATIONS
PUS
Pus contains much granular débris and numerous more or less degenerated cells, the great majority being polymorphonuclear leukocytes—so-called "pus-corpuscles." Eosinophilic leukocytes are common in gonorrheal pus and in asthmatic sputum. Examination of pus is directed chiefly to detection of bacteria.