PLASMODIUM IMMACULATUM OR FALCIPARUM 575 



blood, are always formed in the gut of the mosquito as the first step 

 in sexual reproduction as outlined above. 



Plasmodium Immaculatum or Falciparum. According to Marchiafava 

 and Bignani and Craig this occurs in two varieties, namely, the 

 quotidan and the tertian. These are described by Craig as follows: 

 The quotidian parasite after invading the red blood corpuscles is 

 first indistinct, but later becomes clear-cut and refractive. There 

 are round forms, but the most common form is the ring form. While 

 most observers think that the ring form is only apparent, due to a 

 very thin centre, Craig believes that this type of plasmodium gen- 

 erally forms real rings in the interior of the erythrocytes. Schaudinn 

 believes that the ring form is due to a large vacuole in the centre 

 of the organism. The ameboid motion of the rings is very active; 

 the infected red blood corpuscles are frequently undersized, and 

 they may be crenated. One corpuscle may contain two or three 

 rings. The Plasmodium falciparum assumes the shape which has 

 been likened to a signet ring. This form is brought about by a 

 collection of most of the protoplasm in one point, while the remainder 

 is arranged as a thin circular strip. The pigment first appears in 

 the thickest portion of the signet ring. These formations are more 

 common in the tertian than in the quotidian type. The pigment is 

 rather scanty, but very dark in color, and collected somewhere at 

 the edge of the parasite. Sometimes the pigment consists of a very 

 few distinct granules only. Segmenting forms are rarely seen in 

 the peripheral blood, but they are common in the spleen,, from which 

 they may be obtained by puncture. At the time of segmentation the 

 pigment becomes collected at the centre. There are six to eight 

 very small round or oval merozoites formed. In the circulating 

 blood Plasmodium falciparum forms the crescents, which are so char- 

 acteristic for this variety of malarial parasite. These crescents are 

 curved. Sometimes they fill the greater part of a red blood corpuscle 

 or even protrude out of it at one or both ends, and they may finally 

 show a remnant of the corpuscle as a cap lying in the concavity. 

 The pigment is found in the centre of the crescent, where it is often 

 arranged in a regularly circular manner. The crescents are the macro- 

 gametocytes of the plasmodium falciparum, and a number of observers 

 have seen a binary division of the crescents in the infected blood. 



The tertian subvariety of the Plasmodium falciparum in its early 

 stage after invasion of the blood corpuscles is larger than the quartan 

 subvariety, very highly refractive, and the signet-ring forms are still 

 more marked. Ameboid motion is less rapid. The hyaline forms 

 become pigmented in twenty to twenty-four hours; the abundant 

 pigment consists of very fine reddish-brown granules, which are 

 generally motile. As growth progresses the ameboid motion is lost. 

 Segmentation occurs after forty-eight hours, and the organism then 

 occupies about one-half of the infected cell. From ten to fifteen 

 merozoites are generally formed, sometimes as many as twenty- 



