480 Malaria 



(meroblast), ready to form merozoits, and the gametocytes all 

 exceeding the size of the red blood-corpuscles. It matures in forty- 

 eight hours, but not with mathematic precision. In single infections 

 the greater number of the parasites are of the same age and present 

 the same appearance, but various shapes and ages may be found 

 together. In double infections, with paroxysms every day, para- 

 sites of different ages may be found. 



The youngest form in which the parasite can be observed is that 

 of a tiny ring in a red blood-corpuscle. The periphery of this 

 ring (when the blood is stained with polychrome methylene blue) 

 is outUned with blue, at one side there is a distinct blue dot, and 

 the center appears colorless and like a vacuole. The dot is usually 

 on the side of the vacuole that has the thinner protoplasmic outline. 

 The smallest such rings usually have a diameter equal to about }i 

 the diameter of the blood-corpuscle. The tiny ring-form, or, as 

 it might better be called, the "seal-ring form," continues" until the 



.0) 



SS 





Fig. 182. Fig. 183. 



Figs. 182, 183. — Gametocytes of plasmodium malariae : 85, The macrogametocyte; 



86, the microgametocyte (KoUe and Wassermann) . 



schizont becomes half the diameter of the blood-corpuscle, when 

 its protoplasm has begun to increase so rapidly that the vacuole 

 no longer appears to be so conspicuous. The organism also becomes 

 irregular in shape and is actively ameboid, its protoplasm streaming 

 this way and that when examined in fresh blood. At this time it 

 may be noticed that the infected blood-corpuscle is increasing in 

 volume, sometimes becoming twice the normal size, and also be- 

 coming pale in color. It seems also as though the disk shape of 

 the corpuscle was lost, and it had become swollen into a more 

 spherical — sometimes irregular — form. The parasite, which may 

 still show a relic of its original ring-form, now shows plentifully 

 throughout its protoplasm exceedingly fine granules of yellow- 

 brown pigment. When from thirty-six to forty hours old, all trice 

 of the "seal-ring" form disappears, the ameboid action becomes less 

 marked, and the parasites (now three-quarters the size of the en- 

 larged pale and misshapen corpuscles in which they are contained) 



