. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. 214 THE FLUKES worked on the life history of this species, chiefly at El Marg, near Cairo, Egypt. He found that Schistosoma embryos are attracted by several species of fresh-water snails and that they penetrate the bodies of three species, Bullinus contortus (Fig. 66A), B. dybowskii and Planorbis boissyi (Fig. 66B). Here they undergo transformation into sporocysts, from which daugh- ter sporocysts bud off (Fig. 67). After leaving the mother cyst the daughter sporocysts migrate into the tissue of the liv
. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. 214 THE FLUKES worked on the life history of this species, chiefly at El Marg, near Cairo, Egypt. He found that Schistosoma embryos are attracted by several species of fresh-water snails and that they penetrate the bodies of three species, Bullinus contortus (Fig. 66A), B. dybowskii and Planorbis boissyi (Fig. 66B). Here they undergo transformation into sporocysts, from which daugh- ter sporocysts bud off (Fig. 67). After leaving the mother cyst the daughter sporocysts migrate into the tissue of the liver. Fig. 67. Larval forms of blood flukes teased from liver of Planorbis; A, sporocyst containing daughter sporocysts; B, daughter sporocysts in liver tissue; C, cercaria. Note forked tail, characteristic of Schistosoma cercarise. (After Leiper.) and grow rapidly. They become greatly elongated and eventu- ally ramify throughout the organ, so increasing its bulk and color that an infected snail can be detected at a glance. The sporo- cysts move by wriggling movements, and absorb nourishment directly through the body wall. When they become over- distended with the cercariae developing within them the wall ruptures and the cercariae are set free in the snail. The cercariae are discharged from the mollusc in " puffs," a number being periodically shot into the 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 Chandler, Asa Crawford, 1891-. New York, J. Wiley
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