530 



APPENDIX D. 



the amoebae when inoculated into animals. The following description is 

 chiefly taken from the monographs of the four writers last mentioned. 



Characters of the Amoeba. The amoebae, as seen in ' the stools of 

 a case of amoebic dysentery, are rounded or somewhat irregular proto- 

 plasmic masses, usually measuring about 25 to 35 /x, in diameter, though 

 both larger and smaller forms are met with. 



When the parasite is at rest it has a more or less rounded shape ; 

 the protoplasm is finely granular and of refractile appearance, and is 

 without differentiation into layers. The organism may show sluggish 

 amoebic movements at the ordinary temperature, but these become much 

 more active when a warm stage is used. When they occur, the amoeba 

 shows 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. 

 169, a,b). By the 

 amoebic move- 

 ments slow loco- 

 motion may be 

 produced. The 

 amoebae often show 

 vacuoles in their 

 substance, and may 

 contain numerous 



FIG. 169. Amoebae of dysentery. 



a and b, amoebae as seen in the fresh stools, showing blunt amce 

 boid processes of ectoplasm. The endoplasm of a shows a nucleus, three red 

 red corpuscles, and numerous vacuoles; that of b, numerous red corpuscles f w Viip}-) 



> 



tO 



annpar 

 and a few vacuoles. > 



c, an amoeba as seen in a fixed film preparation, showing a small undergo digCS- 

 rounded nucleus (Kruse and Pasquale). x 600. . \ i -u 



tion), also bac- 



teria, etc. There is a single nucleus which lies in the central part of the 

 organism and usually measures about 6 to 8 //, 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 examination 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 /x, 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 



