PLASMODIUM VI VAX 



marized as follows: — -During the first tWenty-four hours after the 

 entry of the sporozoite or merozoite into the red cell the little 

 trophozoite, which at the beginning is about one-third the size of 

 the erythrocyte, grows rapidly, absorbing nutriment from the red 

 cell by its pseudopodia and by the large surface of cytoplasm ex- 

 posed, owing to the size of the vacuole. 



Hence, not merely does it increase in size, but it acts deleteriously 

 upon the enclosing cell, which loses its haemoglobin, turns pale and 

 degenerates, as is evident by its becoming swollen owing to the 

 absorption of fluid, and by showing, on staining with any modifica- 

 tion of Romanowsky, a dotted appearance due to red granules 

 called Schiiffner's dots. These dots can be seen in red cells affected 

 by other plasmodia — e.g., P. canis in the dog. In growing, it gives 

 rise to a quantity of hsemozoin, which appears as fine, reddish- 

 brown granules, often seen in active movements due to currents in 

 the cytoplasm of the parasite. In about thirty hours it becomes 

 rounded off as the schizont (Fig. 44, p. 294), 8-5 in diameter. 



From the thirtieth to the forty-eighth hour the fully-grown 

 schizont undergoes sporulation, when it will be noticed that fifteen 

 to twenty merozoites are formed, while the hsemozoin granules are 

 packed together, either into the centre or towards the periphery of 

 the parasite. It will also be noted that the red cell is now con- 

 siderably swollen and almost colourless. 



About the forty-eighth hour the remains of the corpuscle dis- 

 integrate, and the merozoites (size 1-5 /^), haemozoin, etc., escape. 



So that P. vivax occupies forty-eight hours in the process 

 of schizogony. As curiosities, it may be mentioned that a 

 trophozoite or a schizont may be seen in the same red cell as a 

 gametocyte. 



Sporogony. — -The development in the mosquito was first worked 

 out in Anopheles claviger. 



The development of the gametes, and the fertilization of the 

 macrogamete, and the structure of the ookinete, have been carefully 

 described and figured by Schaudinn (vide Figs. 45, 46, and 47, p. 294). 

 In about forty hours after the mosquito has been fed, the oocyst can 

 be found as a round transparent body with strands of yellowish 

 haemozoin scattered throughout it, lying in the stomach wall beneath 

 the epithelium, and covered over by the musculo-elastic layer of the 

 gut. Its wall is seen to be Well defined — i.e., the ookinete has become 

 encysted. By this time the chromatin will have divided into small 

 masses. 



On the third day it will have become from one-third to one-fourth 

 larger, and the cyst-wall will be more distinct, and the imperfect 

 segmentation of the protoplasm around the nuclei can be seen. 

 The haemozoin is seen gathered into little masses lying between the 

 segments of the cytoplasm, which are the sporoblasts. The first 

 stages of the formation of sporozoites may also be observed. 



During the fourth day the size increases about a fourth, and the 

 nuclei and their surrounding protoplasm will have formed some 



