FIG. 44. 



A diagram showing the life-history and migration of the Malaria 

 parasite, Laveyania M alarifc , as discovered by Laveran, Ross, and Grassi. 

 The stages above the dotted line take place in the blood of man. The 

 oblong-pointed parasite is seen entering the blood at n just below No. I. 

 The circles represent the red blood-discs of man. Schizogony means 

 multiplication by simple division or splitting, and it is seen in Nos. 6, 7, 8, 

 9, and 10. The stages below the dotted line are passed in the body of the 

 spot-winged gnats of the genus Anopheles. A peculiar crescent or sausage- 

 shaped condition is assumed by the parasite inside the red corpuscle No. VI. 

 These are found to be of two kinds, male and female, Nos. Vila and Vllb. 

 They are swallowed by the spot-winged gnat when it sucks the blood of an 

 infected man. Here in the gut of the gnat they become spherical ; the 

 male spheres produce spermatozoa No. Xa, which fuse with and fertilize 

 the female spheres or egg cells No. XI. An active worm-like form No. XIII 

 results, which pushes its way partly through the wall of the gnat's gut, 

 and is then nourished by the gnat's blood. It swells up, divides internally 

 again and again, and is enclosed in a firm transparent case or cyst, Nos. XIV 

 to XVIII. The cysts are far larger in proportion than is shown in the 

 diagram, and are visible to the naked eye. The final product of the 

 breaking up, which is called sporogony, is a vast number of needle-shaped 

 spores or young (called Exotospores, as opposed to the Enhaemospores, 

 which are formed in the human blood, as seen in Nos. 9 and 10, and serve 

 there to spread the infection among the red corpuscles). The needle- 

 shaped spores formed in the gnat's body accumulate in its salivary glands, 

 and pass out by the mouth of the gnat when it stabs a new human victim 

 who thus becomes infected, No. XIX. 



Had the sausage-like phases Nos. Vila and Vllb been swallowed by a 

 common gnat or mosquito of the genus Culex they would have been 

 digested and destroyed. It is only in species of gnats of the kind known 

 as Anopheles that the parasite can undergo its sexual development and 

 subsequent process of the formation of cysts and needle-shaped exoto- 

 spores. (After Minchin in Part I. of Lankester's "Treatise on Zoology," 

 published by A. and C. Black.) 



