70 



Mr. E. H. Ross. 



[Jan. 23, 



two or even three parasites may occur in the same cell. The parasite, 

 in this early stage, contains a double purple dot (figs. 1,2); in this phase 

 it resembles the Leishman-Donovan bodies found in human leucocytes in 

 cases of Kala Azar. When first seen the dot is motionless, but after a time 

 on the jelly, as the lymphocyte host becomes disorganised, it may show some 

 Brownian movement. In the next stage the parasite is larger, and the 

 chromatin dot has divided into two or more dots until the sphere-like sac 

 may be packed with them (fig. 3). Then each dot becomes dumb-bell 

 shaped (fig. 4), and again, by a simple process of elongation, rod shaped 

 (figs. 5, 6, 7). The parasite may contain one of these rods (fig. 9), or it may 

 be full of them — the actual numbers varying in different examples. Some- 

 times a parasite may contain one or more rods, some dumb-bells, and some 

 dots. But the size of the parasites increases steadily with these successive 

 stages of the development of their contained chromatin (compare figs. 1 

 and 15). Dining the rod formation, the smaller subsidiary vacuoles already 

 mentioned appear in the cytoplasm of the host cell (figs. 3, 5, 12) ; they 

 never contain any chromatin and remain unstained. With its growth the 

 parasite begins to compress the nucleus of the lymphocyte (figs. 13, 14), 

 and the wall of the latter can be seen as a shell enclosing the parasite 

 (figs. 14, 15, 16). The rods grow longer and thicker (figs. 8, 9, 10) until 

 they stretch across the parasite, and their ends may be doubled against its 

 wall, and they may then present in optical section an erroneous impression 

 of flattening or a terminal bulging (figs. 8, 13, 14). In the next stage a 

 stout fiagellum grows out from both ends of the rod (figs. 8, 11, 12, 13), 

 which becomes rolled up in a coil within the sphere (figs. 13, 14, 15). 

 The rod with its two flagella splits longitudinally in its whole length 

 (figs. 8, 12), and this process of splitting takes place again and again. The 

 fission throughout is always lengthwise, never transverse. A specimen in 

 this stage will show the parasite, now equal in size to the original dimensions 

 of its host-cell, bulging the wall of the latter, compressing the nucleus into 

 a small space, and containing within its interior a mass of woven, twisted, 

 and intertwined purple threads, a conglomerate maze of worm-like spirilla 

 stained red by the Azur dye (figs. 15, 16). 



Arrived at its maturity, the parasite breaks away from the shell of its 

 host-cell and then bursts, setting free the threads into the plasma (fig. 17). 

 But the flagellate forms, owing to the fact that they are stained, are dead 

 and motionless, and they may remain attached to the shrunken sphere sac, 

 their ends waving in the currents set up. 



It was found very difficult to demonstrate the motile, flagellate forms of 

 the parasite when free in the blood. They cannot be seen then by the 



