774 PATHOGENIC PROTOZOA 



lacking the vacuole, shows a greater amount of hemozoin, which is 

 never concentrated in the. center of the parasite but is scattered 

 equally throughout the body. The cytoplasm of the sporont is less 

 fluid than that of the schizont and shows no tendency to ameboid 

 motion. The chromatin is relatively large in amount and, although 

 broken up more or less into granules and threads, shows no real ten- 

 dency to segment or disperse, but remains a compact mass. 



The quartan parasite, when stained with Wright's or a similar 

 preparation, shows quite regular and symmetrical segmentation, usu- 

 ally into eight merozoites. The distinction between schizont and 

 sporont and between male and female gametes may be made on the 

 same grounds as in tertian. 



In aestivo-autumnal fever the chromatin dot in the young ring is 

 often doubled, or even trebled, and in general is large and stains 

 brilliantly. The adult and half -grown gametes may be differentiated 

 into male and female by the criteria already given. 



The Examination of Fresh Blood. Directions have already been 

 given (Chap. LIX) for making wet preparations and if, by ringing 

 the cover-glass with vaseline, drying be prevented, the preparations 

 will keep and may be studied for hours. In tertian fever the young 

 ring forms are at first difficult to detect, unless the amount of light 

 going through the microscope be cut down to the minimum. As the 

 parasite grows older, an increasing number of hemozoin granules ap- 

 pear, and since they are in constant motion the parasite is readily de- 

 tected. Its cytoplasm is delicate, and with very young parasites is 

 difficult to distinguish from the red cell itself ; older parasites, however, 

 develop pseudopods, which are constantly projected and retracted, and 

 the entire organism shows active movements, rendering it easy to see. 

 The pigment continues to increase, and in the gametes is abundant 

 and in constant motion; the gametes, however, fail to show any ame- 

 boid changes, and the protoplasm is stiff and rigid with a regular, un- 

 broken margin. At times a clear refractile spot is seen, which is the 

 nucleus. The infected erythrocyte is pale and swollen. Even in un- 

 stained preparations the sexes may be distinguished ; the microgameto- 

 cyte is about the size of a red cell, the cytoplasm is hyaline, and after 

 the preparation has been made ten to twenty minutes the flagella, or 

 microgametes, . may be seen thrashing about in the parasite. After 

 repeated attempts four to eight microgametes rupture the cell and 

 emerge. The macrogamete is larger than a red cell and is finely 

 granular and no exflaggelation of microgametes occurs. 



