. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. MODE OF INFECTION 133 but they are eventually passed out with the feces. Unhke amebae in the vegetative stage, the encysted amebs are resistant to drying and may live for at least a month in dried or partially dried faeces if not exposed to direct sunUght. They are not, how-. FlQ. 38. Comparison of Endamteba histolytica and E. coli. x 1500. A, E. histolytica, vegetative stage; note small indistinct nucleus (n.), clear ectoplasm (ec), ingested red corpuscles (c.) and contraoticle vacuole (c. v.). B, E. c
. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. MODE OF INFECTION 133 but they are eventually passed out with the feces. Unhke amebae in the vegetative stage, the encysted amebs are resistant to drying and may live for at least a month in dried or partially dried faeces if not exposed to direct sunUght. They are not, how-. FlQ. 38. Comparison of Endamteba histolytica and E. coli. x 1500. A, E. histolytica, vegetative stage; note small indistinct nucleus (n.), clear ectoplasm (ec), ingested red corpuscles (c.) and contraoticle vacuole (c. v.). B, E. coli, vegetative stage; note large distinct nucleus (n.), indistinctness of ectoplasm, com- mon absence of ingested food materials and of contractiole vacuole. A', E. histo- lytica, cyst; note small size (10-14 m). four nuclei (n.), and "chromidial body" (chr.). B', E. coli, cyst; note large size (15-20 /i), and eight nuclei (n.). ever, so resistant to drying as are the cysts of many free-living amebse. In this condition the amebae may be blown about by the wind, may contaminate garden vegetables where " night-soil" is used as fertilizer, or may be carried on the feet ^,â¢j^ ^. of flies. If by any of these or other means ^^ ^P they reach human food or water and thus secure entrance to the digestive tract, the Fig. 39. Precystic stage of E. histolytica, sometimes mistaken for cyst wall is dissolved by the pancreatic juice, a distinct species and ,. I' 1 1 j_ ⢠â r named X 7 50. and four little amebae, each containing one of (After Woodcock and the daughter nuclei which were formed when Penfoid.) the cyst first developed, are set free in the intestine and begin to grow and multiply. The active vegetative amebae from an acute case of dysentery are destroyed in the stomach if swallowed, and cannot reach their feeding grounds in the large intestine;. Please note that these images are extracted from scanned page images that may have been digitall
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