4 88 DYSENTERY. 



differentiation into a central granular endoplasm and an 

 outer hyaline layer or ectoplasm which is very thin and 

 well marked off from the former. The blunt processes 

 which are protruded in amoebic movement are composed 

 of the ectoplasm (Fig. 108). By the amoebic movements 

 slow locomotion may be produced. The amoebae often 

 show vacuoles in their substance, and may contain numerous 

 red corpuscles (which appear to undergo digestive lique- 

 faction), also bacteria, etc. There is a single nucleus 

 which lies in the central part of the organism and usually 

 measures about 6 to 8 /x in diameter. It is round or oval 

 and contains a nucleolus. In the living condition the 

 nucleus is invisible or is faintly seen, but becomes very 

 evident on the addition of acetic acid, etc. The amoebae 

 break down pretty rapidly outside the body, and examina- 

 tion of the dysenteric stools twenty-four hours after being 

 passed, usually fails to detect any of them. It is only on 

 one or two rare occasions that the process of division of the 

 amoebae has been observed and described. 



By some there have also been described encysted forms. 

 These are of smaller size, about 10 to 15 /j,, with a well- 

 marked capsule, sometimes showing a double contour and 

 a central protoplasm in which a nucleus may or may not 

 be visible. It is still doubtful, however, whether these 

 structures really constitute a stage in the development of 

 the organism, as direct transformation from the one form 

 into the other has not been observed. 



Distribution of the Amoebae. As already stated, they 

 are usually found in large numbers in the contents of the 

 large intestine in tropical dysentery. They also, however, 

 penetrate into the tissues, where they appear to exert a well- 

 marked action. They are found in the mucous membrane 

 when ulcers are being formed, but their most characteristic 

 site is beyond the ulcerated area, where they may be seen 

 penetrating deeply into the submucous, and even into the 

 muscular coats. In these positions they may be unattended 

 by any other organisms, and the tissues around them show 

 more or less necrotic change without much accompanying 



