372 THE ETIOLOGY OF TROPICAL DISEASES 



of man, and the parasite reappears in the blood of the individual so 

 inoculated. It is interesting in this connection to observe the 

 negative results of the recent attempts of Koch to inoculate the 

 higher apes with malaria in Batavia, as reported by the German 

 Colonial Office.* Laveran's bodies have been variously classified as 

 knowledge of them has grown. It is now agreed that these parasites 

 belong to the Sporozoa, to the order of Hmmocytozoa, and to the 

 genus of Hcemamceba. 



Now if we examine a sample of human blood from, say, the 

 benign tertian form of malaria, we shall find not different parasites 

 as in three forms named below, but different stages in the evolution 

 of one parasite. These different stages are normal and regular, and 

 not accidental or chance forms, and for the sake of convenience we 

 may summarise them seriatim thus : — 



1. Early Form of Parasite. — Looking through the microscope, we 

 shall readily observe large numbers of blood corpuscles, and in some 

 of these, and possibly many of them, there will be apparent certain 

 irregularities. In the first place, the protoplasm of the affected 

 corpuscles is paler than that of the healthy cells. Next, within the 

 protoplasm will be seen the parasite iamcebula), containing possibly a 

 few specks of black pigment, and of more or less irregular outline, 

 sometimes nearly filling the whole blood corpuscle. This body is 

 motile, and moves about like an amoeba inside the corpuscle, in the 

 tertian fever with great rapidity, As it increases in size, the 

 corpuscle becomes paler. The largest of these spherical forms are 

 outside the cells (extra-corpuscular spores, enhsemospores), and move 

 about free in the blood plasm. But the smaller ones are generally 

 inside the blood cells (intra-corpuscular amoebula). They live at the 

 expense of the haemoglobin in the corpuscle, and ultimately change 

 it into pigment (melanin), 



2. Concentration of the Pigment. — ^After the parasite has gained 

 its mature form as regards size, an increase and concentration of the 

 pigment occurs. The body of the parasite now fills the corpuscle, 

 and the pigment which before existed in specks, or diffusely, becomes 

 gathered together towards the centre of the parasite. 



3. The third change in the evolution of the amcebula is segmenta- 

 tion. By this process the parasite splits up into segments; the 

 tertian fever forming much smaller and more numerous segments 

 than the quartan. This segmentation gives rise to what is known 

 as the " rosette body," 



4. In reality these segments are sporocytes, new amoeboid bodies, 

 which, by the rupture of the eaten-out corpuscle, become diffused 

 freely in the blood. Many of these " spores " are supposed to pass 

 to the spleen, some are absorbed by phagocytes or scavenging cells, 



* Deutsche Medicinische Wochenschrift, February 1900. 



