298 



PARASITIC PROTOZOA IN RELATION TO THE WAR. 



one or more of the parasites named as occurring- in the intestine 

 were present, there beinis:- both single and multiple infections, 

 while there was a periodicity in the appearance of the different 

 parasites in the successive stools of the same patient. 



Some of these intestinal Protozoa may now be briefly consi- 

 dered : — 



Intestinal Entamcebae. 



The best known of the protozoal dysenteries is that due to 

 Entantccha histolytica. This organism, which is polymorphic, is 

 the excitant of amoebic dysentery. Its life-history, as now 

 accepted, has been elucidated more particularly by Darling, and 

 by James and Deeks in the Panama Canal Zone, while its suc- 

 cessful treatment by emetine has been brought forward chiefly by 

 Rogers and by Vedder. 



Entama'ba histolytica, sometimes called with doubtful accu- 

 racy Endam<£ha dysenteria:, is found in freshly voided stools that 

 are usually blood-stained and contain strings of mucus. The enta- 



Fig. 2. 



Fig. 1. 



moebae when active show pseudopodia. at first chiefly composed of 

 ectoplasm. The endoplasm often contains ingested red blood- 

 corpuscles and other debris. The nucleus in large trophozoites 

 (or growing, feeding amoebre) may be seen with difficulty, but in 

 the form of the organism that used to be termed E. tetragena 

 the nucleus may show a karyosome and a centriole (Fig. i). The 

 entamoeba multiplies by binary fission, and occasionally by multiple 

 fission or schizogony, when four merozoites or daughter forms 

 are produced. Encystment occurs, and the round cysts finally 

 produced measure about io/a* to 15/1 in diameter, though strains 

 with small cysts about 7/a to io/a in diameter are known. The 

 mature cysts contain four nuclei, as well as darkly staining masses 

 variously known as chromidial, chromatoid, crystalloidal, or side- 

 rophile bodies (Fig. 2). The quadri-nucleate cyst is charac- 

 teristic, and is the infective stage. When the cyst is hardly mature 



* I M denotes i micron, or i^?nT millimetre. 



