MALARIA. 373 



cells are spherical. A distinct cell-membrane, visible as a 

 double contour, is not peculiar to most varieties. The proto- 

 plasmic body is relatively small in the juvenile forms, the 

 nucleus preponderating. In the older cells these conditions are 

 reversed. In the living parasites, especially at an early period, 

 nucleus and plasma are usually not differentiable. In stained 

 preparations (p. 393) the unstained nucleus is clearly distin- 

 guishable from the deeply stained cell-body. Differentiation 

 into an outer layer of cytoplasm (ectoplasm) and a central 

 portion (entoplasm) is, on the whole, not practicable. The 

 plasma appears mostly homogeneous and hyaline, although ma- 

 ture parasites at times present dense, slightly refractive granula- 

 tions. In the older cells the substance of the plasma generally 

 contains from a brownish-red to a black pigment the malarial 

 pigment, or melanin, which is considered a digestive product of 

 hemoglobin. This assumes the form in part of fine, dust-like 

 particles, in part of coarser granules; or it appears as delicate 

 needles up to i /z in length.' The pigment often exhibits a 

 peculiar dancing and wriggling movement, which only resembles, 

 but is not identical with, the Brownian molecular movement, and 

 is believed to be an active motor procedure. In addition to the 

 ameboid movement and that of the pigment the malarial para- 

 sites are characterized by a third mode of motion namely, that 

 dependent upon flagella. From the fully developed round 

 parasite arise flagella that move actively, in part become free, 

 and then retain their motility. According to Kruse, these 

 structures must be considered as evidences of degeneration. In 

 addition to pigment the cell-body of the malarial parasites fre- 

 quently contains vacuoles, mostly small and few. Often difficult 

 of differentiation from these is the relatively large, vesicular, 

 generally eccentric nucleus, which in the living cell is only 

 recognizable by its distinct contour, and in stained preparations 

 exhibits no nuclear . membrane, but a distinct deep-black 

 nucleolus at the periphery. The nucleolus is often surrounded by 

 a feebly stained zone, while the nucleus itself does not take the 

 stain. Kruse, upon the basis of his investigations, does not 

 admit the significance of this large nucleus, but he considers the 

 nucleolus as the nucleus. 



Laverari 's Crescents. Morphologically distinct from these 

 simple forms of malarial parasites (corps spheriques of Laveran) 

 are the crescents of Laveran (corps en croissant) and the spher- 

 ical and spindle-shaped bodies related to them (spheres of the 

 crescentic series). The crescents have the shape of a half- 

 moon, are from eight to ten microns long, at the middle from two 

 to three microns thick, and are characterized by a considerable 

 degree of refractive power. They always contain pigment, 

 usually in abundance, but sometimes only a few granules. This 



