. Parasites and parasitosis of the domestic animals : the zoo?logy and control of the animal parasites and the pathogenesis and treatment of parasitic diseases . Domestic animals. PLATYHELMINTHES 161. Fig. 87.—Left to right, Fasciola hepatica, F. americanus, Dicrocoelium lanceatum; natural size (drawn from author's speci- mens) . After a period of embryonal development, which will only occur pro- viding the eggs have reached water and suitable conditions of tempera- ture, the larva escapes by the lifting of the operculum of the shell. It is then in the stage of the miracidium (Fig. 88, 2), an
. Parasites and parasitosis of the domestic animals : the zoo?logy and control of the animal parasites and the pathogenesis and treatment of parasitic diseases . Domestic animals. PLATYHELMINTHES 161. Fig. 87.—Left to right, Fasciola hepatica, F. americanus, Dicrocoelium lanceatum; natural size (drawn from author's speci- mens) . After a period of embryonal development, which will only occur pro- viding the eggs have reached water and suitable conditions of tempera- ture, the larva escapes by the lifting of the operculum of the shell. It is then in the stage of the miracidium (Fig. 88, 2), an infusorian-like organism, ciliated, elongated, broader in front, and about 130 microns in length. During its free-swimming period it must meet with a suitable host within a few hours or it will perish. This host is a small snail, usually of the genus Limnsea (L. humilis) into which the larva bores its way by a perforating rostrum at its anterior extremity. If it escapes its aquatic enemies during this free stage and arrives at a suitable location within the snail, usually the pulmonary chamber, the larva loses its cilia and digestive tube and becomes transformed into a sporocyst (Fig. 88, 3)—a sort of reproductive sac, ovoid in form and acquiring a length of about mm. The cyst now becomes filled with germ-cells which are disposed in masses (morula) ordinarily five to eight in number. The masses of germ-cells become transformed into so many redice (Fig. 88, 5 and 6) which may be seen in different stages within the cyst. The redise are cylindrical in form and have a simple intestine and pharynx with lips turned out like a sucker. When they have attained a certain stage of development the redise become actively motile, finalh^ rupturing the maternal cyst aiid passing to another organ of the snail, "usually the liver, in which location they grow to a length of mm. Within the body of the redia are germ-cells formed into six to ten cellular masses which are t
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectdomesti, bookyear1920
