. Civic biology; textbook of problems, local and national, that can be solved only by civic coöperation. Biology. 264 CIVIC BIOLOGY Tapeworms of the dog — T&nia echinococcus. Unfortunately our faith- ful friend has been found to harbor twelve different species of tapeworms. The most dangerous of all is T. echinococcus, which has a different life history and mode of growth from those just described (see Figs. 116,117). The adult worm is minute (from to 6 millimeters long) and occurs only in the dog, wolf, and jackal, often in enormous numbers. The cysticercus stage is found in twenty-se
. Civic biology; textbook of problems, local and national, that can be solved only by civic coöperation. Biology. 264 CIVIC BIOLOGY Tapeworms of the dog — T&nia echinococcus. Unfortunately our faith- ful friend has been found to harbor twelve different species of tapeworms. The most dangerous of all is T. echinococcus, which has a different life history and mode of growth from those just described (see Figs. 116,117). The adult worm is minute (from to 6 millimeters long) and occurs only in the dog, wolf, and jackal, often in enormous numbers. The cysticercus stage is found in twenty-seven different mammals, including num. Instead of forming a cyst with a single sco- lex, or head, this worm forms a cyst that may grow for several years, to the size of a goose egg or even a " child's head," and its wall forms num- bers of vesicles which may develop hundreds of scolices. Dogs infested with this tapeworm should he, mercifully killed and cremated, and dogs, generally, should not be permitted to lick the face or hands or to eat out of dishes used by man. Tapeworms of fishes — Dibothriocephalus latus. Fishes harbor a number of tapeworms, which, chiefly in oriental countries, naturally find their way into men, who consider raw fish a delicacy. The broad tapeworm, D. latus, is found in the muscles of various fresh-water fishes, among them the pike, salmon, and perch. Tapeworms vary in size from almost micro- scopic to ribbons half an inch broad and many feet in length, but this signifies little. The rate of growth for T. saginata and D. latus has been determined as 7 centimeters and 8 centimeters per day respectively. At this rate, in thirty-five years a broad tapeworm might grow to be. FHi. 110. Dog tape- worm (T. echinococ- ci<s),twenty-five times natural size After Braiui . feet in length. Roundworms (nematodes) and threadworms (nemathelminthes) {nemOy " thread ^'; helminthes, ** worms*'). These worms attack plants, all sorts of animals
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