46 PROTOZOAN PARASITISM 



pink or practically unstained, the outlines of the 

 organism being somewhat indistinct at times. The 

 endoplasm is a deeper pink, granular, and if red blood 

 corpuscles are present they are rounded bodies re- 

 taining the black stain in proportion to the differentia- 

 tion. The nucleus is here seen in characteristic form, 

 from 4 to 7 microns in diameter, depending on the size 

 of the amoeba. It is round, has a delicate but defi- 

 nite rim and a linin network, more imaginary than 

 distinct as a common thing. Small chromatin gran- 

 ules are evenly distributed on the inner aspect of 

 the rim and the karyosome is a minute chromatin 

 body, centrally placed and surrounded by a ''halo," 

 which is more or less distinct. Such a stained am- 

 oeba may be readily identified. 



The cysts vary in size according to the race, the 

 different races averaging 6.6, 8.3, 11.6, 13.3, and 15 

 microns, as measured by Dobell and Jepps (1917- 

 1918). They are round glassy or hyaline bodies in 

 the fresh unstained state. With careful adjustment 

 of the lighting the nuclei may be brought out as deli- 

 cate refractive rings, four in number in the developed 

 cyst. The chromidial bodies, characteristic of the 

 species, may also be made out in such specimens by 

 careful adjustment of the light. The main differen- 

 tial measure, upon which cysts of this amoeba may be 

 identified immediately, without staining, is that of 

 counting the characteristic nuclei. 



In the iron-haematoxylon preparation these cysts 

 are well stained, the cytoplasm light, the nuclei of 



