. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. 138 AMEBiE and it is not improbable that they will prove to be of wide geo- graphic distribution, and often mistaken for Endamceba or flagel- lates, according to the phase of existence in which they are observed. The Parasites. — As already remarked, Craigia resembles some of the free-living soil amebae in that it passes through a flagellated stage, but it differs from them in having only a single flagellum instead of two. Briefly the life history of Craigia hominis (Fig. 40A to F) is as follows: the ad
. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. 138 AMEBiE and it is not improbable that they will prove to be of wide geo- graphic distribution, and often mistaken for Endamceba or flagel- lates, according to the phase of existence in which they are observed. The Parasites. — As already remarked, Craigia resembles some of the free-living soil amebae in that it passes through a flagellated stage, but it differs from them in having only a single flagellum instead of two. Briefly the life history of Craigia hominis (Fig. 40A to F) is as follows: the adult form (Fig. 40E), resembling a typical ameba, is about half the size of the dysentery. g n 1 J —"A Fig. 40. Life cycles of Craigia. C. hominis (A to F). A, swarmer just escaped from cyst; B, young flagellated form; C, mature flagellated form; D, same, dividing; E, amebic form before encystment; F, cyst with swarmers. C. migrans (G to L). G, swarmer just escaped from cyst; H, young flagellated form; I, mature flagellated form; J, amebic form developed by transformation from I, without any multiplication; K, mature amebic form, ready to encyst; L, cyst with swarmers (note larger size and smaller number of swarmers than in C. hominis). X 1000. (After Barlow.) ameba (10 to 25 fx (2Vot> to ToVo of an inch) in diameter), and when moving exserts several blunt pseudopodia. In addition to the nucleus it possesses a structure, possibly a parabasal body, which appears as a bright glistening object in the living animal and stains deeply with nuclear stains. The animal multiplies by simple division for a time, but eventually encysts, rotating on its axis during the process of forming the double-walled cyst. When fully developed the cysts (Fig. 40F) are considerably larger than those of the dysentery ameba (15 fi (tsVo °f an inch) in diameter) and contain about 40 round refractive bodies, which. Please note that these images are extracted from scanned page images that may hav
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmedical, bookyear1918
