776 THE ELEMATOZOON OF MALARIA 



body ; sometimes it is a mere movement of oscillation, sometimes a true 

 movement of translation. 



Certain flagella show a slight pear-shaped swelling at their free extremities. 



At a given moment the flagella detach themselves from the spherical bodies 

 and, becoming free, move about among the red cells in the field of the micro- 

 scope. As soon as the flagella have separated the spherical bodies lose their 

 shape and the grains of pigment in them collect together in a mass. 



Morphologically, the flagellated bodies represent microgametocytes and the 

 flagella the microgametes (vide infra). They are never formed in the circulating 

 blood, but appear very soon in blood which has been withdrawn from the 

 vessels and equally quickly disappear from it. Their complete life-history 

 can only take place in the alimentary canal of certain mosquitos. 



The method of examining blood for flagella. In examining blood for the flagellated 

 forms of the parasite it is advisable to let the blood stand for a few minutes after it 

 leaves the body. Collect a small drop of blood on a slide which has been moistened 

 by breathing upon it, and if possible from a patient in whose blood the crescent 

 forms are numerous, spread it rapidly with a needle and invert it on to a moist 

 chamber made by placing a thick fold of blotting-paper soaked in water, and 

 from the centre of which a rectangular piece about 2 '5 cm. x 1/5 cm. has been cut 

 out, on a sheet of glass. Manson recommends leaving the slide under these con- 

 ditions for 1515 minutes, then dry in the flame, fix in absolute alcohol, wash 

 in 20 per cent, solution of acetic acid in water to dissolve the haemoglobin, wash in 

 water, stain according to the directions given above, dry and mount. 



The life-history of the malarial parasite. 



Like the Coccidia, the hsematozoon of malaria has two methods of repro- 

 duction. 



1. Asexual reproduction or schizogony, which occurs in the blood of the 

 human subject. 



2. Sexual reproduction or sporogony, which takes place outside the human 

 body in the alimentary canal of certain mosquitos of the genus Anopheles 

 (Ross, MacCallum, Laveran, Manson, Grassi, Bignami and Bastianelli, and 

 others). 



(a) Schizogony or asexual cycle. The intra-corpuscular amoeboid parasite 

 spherical body or schizont having reached maturity undergoes schizogony. 

 The nucleus divides into a number of daughter nuclei which pass towards 

 the periphery of the parasite, and the protoplasm also divides by means of 

 sulci passing in from the periphery ; thus the schizont assumes a daisy or 

 marguerite appearance, the pigment accumulates in the centre and the seg- 

 ments marked off by the segmentation of the daisy-shaped body constitute 

 the merozoites. These are set free in the blood stream by the rupture of the 

 red cell and attaching themselves to other red cells, penetrate the latter, 

 grow, become pigmented and again form adult schizonts. 



Schizogony occurs over and over again, and by this process of endogenous 

 reproduction the parasite multiplies in the tissues with extreme rapidity : 

 in tertian fever, for instance, a new generation is produced every other day. 

 The onset of the fever coincides with the discharge of the merozoites into 

 the blood stream. 



(/2) Sporogony or sexual cycle. Besides the amoeboid bodies and the 

 daisy forms (schizonts), gametes represented in one species by crescents, and 

 in other species by/ree spherical bodies larger than the schizonts, are found 

 in the blood of malarial patients : these gametes, whether crescent-shaped 

 or spherical, are derived " from merozoites which, exhausted by a long series 

 of schizogonic multiplications, have, for this reason, undergone evolution in 

 another direction " (Blanchard). 



