. 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 Endammha 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-Uving soil amebse 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 adul
. 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 Endammha 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-Uving soil amebse 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. Fig. 40. Lite 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; B, 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; /, amebic form developed by transformation from 7, 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. (.\fter Barlow.) ameba (10 to 25 yu (^yVo to tAt 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 At (tAt of 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 have been digitally enhanced f
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