. Elementary biology, animal and human. Biology. ADDITIONAL ANIMAL STUDIES 181 136. Relatives of the earthworm. — Two forms of animals that formerly were classed with the earthworm under the head of "worms " are the tapeworm (Fig. 129) and trichina. The tape worm is some- times present in beef and trichina (Fig. 130) in pork. .Meats, there- fore, should be well cooked to kill all such parasites. The trichina, if it gets into the. human systern, causes great suffering. When a tapeworm becomes attached to the human intestine by the suckers and hooks on its anterior end, it is diffi- cu
. Elementary biology, animal and human. Biology. ADDITIONAL ANIMAL STUDIES 181 136. Relatives of the earthworm. — Two forms of animals that formerly were classed with the earthworm under the head of "worms " are the tapeworm (Fig. 129) and trichina. The tape worm is some- times present in beef and trichina (Fig. 130) in pork. .Meats, there- fore, should be well cooked to kill all such parasites. The trichina, if it gets into the. human systern, causes great suffering. When a tapeworm becomes attached to the human intestine by the suckers and hooks on its anterior end, it is diffi- cult to dislodge. D. Mollusca 137. Fresh water mussel. — The fresh water mussels are moUusks that are sometimes called clams. They are often quite abundant on the bottom of creeks, rivers, ponds, or lakes. Usually they are partly covered with sand or mud, sometimes even more than is shown in Figure 131. It will be seen at once that the mussel is inclosed by a shell. This consists of two parts called valves; hence these animals, as well as salt water nlussels, clams, and oysters are called bivalves (Latin bis = two + valve). The two valves are held together along one margin by a tough material that serves as a hinge. On each valve near the hinge, a promi- nence, known as the beak or umbo, may be readily seen. Around. B, tapeworm, about 15 feet longi omitted portions being indicated Fig. 129. — The tapeworm. (Shipley and MacBride.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Peabody, James Edward, b. 1869; Hunt, Arthur Ellsworth, joint author. New York, The Macmillan company
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