A. Entozoa or Internal Parasites, their general characters and effects. I. Protozoa. (1) Amoeba. (2) Coccidia. (3) Haematozoa of malaria. II. Trematoda or Flukes, chiefly Distoma hepaticum, sinense, and haematobium. III. Cestoda or tape-worms. (1) Taenia solium, structure and development r Cysticercus cellulosae, its scolex form. (2) Taenia mediocanellata. (3) Taenia echinococcus, forming hydatids; its cysts, brood-capsules, heads and laminated membrane. (4) Bothriocephalus latus. Other tape-worms. IV. Nematoda or Round-worms. (1) Trichina spiralis, its embryonic and adult forms; effects of migrations. (2) Ascaris lumbricoides. (3) Oxyuris vermi-cularis. (4) Trichocephalus dispar. (5) Dochmius duodenalis. (6) Filaria medinensis. (7) Filaria sanguinis, its periodicity in the blood; relation to chylous urine and lymph-scrotum.

B. Epizoa or External Parasites. (1) Arachnidae, chiefly Acarus scabiei and Pentastomum denticulatum. (2) Insecta, chiefly Pediculi and Pulex irritans. Larvae of insects in wounds, skin, and bowels.

THE Animal Parasites represent a much wider extent of the animal kingdom than the vegetable parasites do of the vegetable kingdom. We have the lowliest forms of animal life, the protozoa, comparable with the bacteria in respect that they are unicellular organisms, and we have animals as highly organized as the Insects. With this great variety in organization we have also great differences in seat, effects, and other characteristics.

The Animal Parasites live in or on the living tissues of the affected animal, which is called their host. They produce their effects, partly by using up the nutritive material of the body, partly irritating and injuring the structures, and partly also, as is probable in some instances, by producing toxic agents. This last is, however, in the case of the animal parasites, a very infrequent effect as compared with that of vegetable parasites.