LAVERANIA. 263 



Schiiffner's dots. Sooner or later hsemozoin pigment appears 

 in the growing trophozoite, the pigment being dark brown or 

 black, and is collected into a distinct round mass, and this 

 early collection of the pigment into a round compact mass 

 in the preschizogonic stages is a diagnostic feature of the 

 asexual forms of this species. 



All the infected corpuscles soon disappear from the peri- 

 pheral circulation, and schizogony takes place almost exclusively 

 in the internal organs. Sometimes this takes place before 

 pigment has formed, at others not till some growth has taken 

 place and pigment granules have developed in the cytoplasm. 

 It was probably this that led the earher observers to describe 

 two separate species of malignant tertian parasities (P. malarise 

 'prsecox and P. malarise, immaculatum) . The pigment granules 

 run together to form a dark granular mass at one side of the 

 parasite. The fully developed schizont occupies one-half to 

 two-thirds of the diameter of the red blood-corpuscle, and gives 

 rise to 8 to 24, usually 10 to 20, very small merozoites. Sometimes 

 a larger number, up to 32, are set free, but this may be due to 

 two schizonts being contained in a single corpuscle. The 

 merozoites are arranged in a grape-like cluster (" rosette ") 

 round a central residual mass, with a considerable amount of 

 pigment. 



The attack of malaria synchronizes with the setting free of 

 the merozoites, but the three stages of the attack are not so 

 sharply defined as in the case of P. vivax infections. The fever 

 may occur every forty-eight hours (tertian) or every twenty-four 

 hours (quotidian) . In the latter case it is probably due to two 

 infections having originally taken place, schizogony due to 

 each taking place on alternate days, causing a daily attack of 

 fever. In certain cases of heavy infections schizonts are seen 

 in the peripheral blood along with the trophozoites ; and this 

 is usually an indication that the infection is a very serious 

 one and may prove fatal. Schizogony may be seen in a certain 

 number of ordinary infections in thick blood-films ; but it 

 can, however, be studied best in cultures or by carrying out 

 spleen punctures during the acute phases of the attack. 

 After schizogony, which, as remarked above, usually takes 

 place in the internal organs, ring-forms appear again in the 

 peripheral blood. 



to a coarse network, with sporozoites commencing to 

 form as finger-like buds ; U, sporozoites fully formed and 

 attached to several masses of cytoplasm into which the 

 network has broken, two residual masses containing 

 nuclear matter also present ; V, detached sporozoites 

 irregularly distributed in the oocyst, which ruptm-es, 

 liberating them into the ccelomic cavity ; W, sporozoites 

 entering the salivary glands ; X, sporozoites injected 

 into man by the mosquito : they invade the red blood- 

 corpuscles and start the schizogony cycle. (After Wenyon.) 



