280 THE INFECTIOUS DISEASES. 



The latter often take the form of small rings surrounding a central clear 

 space. This is especially well seen in stained specimens (Plate I., Figs. 

 1-4). If the blood be again examined some hours later, these very small 

 forms will have grown to a considerable extent, and small brown or black 

 granules will be noted in the body of the plasmodium. This pigment has 

 a very rapid motion inside the body of the parasite. If the blood be ex- 

 amined at intervals for forty-eight hours the organism may be seen to 

 have grown so large as to occupy nearly the whole of the red cell (Plate 

 I., Figs. 5-12), which becomes somewhat swollen and pale, the latter effect 

 being due to the destruction of the haemoglobin of the cell by the para- 

 site, which thus produces the pigment granules of melanin with which it 

 is filled. At the end of forty-eight hours the pigment has collected in 

 the centre of the organism, which has ceased its active amoeboid motion. 

 Now small pale spots, which are the nuclei of the segmenting mature 

 form, become easily visible (Plate I., Fig. 16), and finally the red cell 

 bursts, and the small rnerozoites, each containing a nucleus, are set free 

 to enter other red cells and to repeat the cycle in another period of forty- 

 eight hours. A certain portion of the free merozoites are destroyed by 

 the phagocytic leucocytes and other cells. The free pigment left after 

 the segmentation of the mature forms is also collected by these phago- 

 cytes. Thus after severe and prolonged attacks of malaria the leucocytes 

 are frequently filled w T ith pigment. 



The quartan organism goes through a cycle similar to that of the ter- 

 tian, except that the time required is seventy-two instead of forty -eight 

 hours. There are also a few minor differences in the morphological ap- 

 pearance of the two organisms. Thus the small early amoeboid forms 

 of the plasmodium are much more active in their movements in the ter- 

 tian than in the quartan. The pigment in the tertian is very fine ; in 

 the quartan it is often in small blocks or rods and is much coarser 

 (Plate I., Figs. 22-25). The mass of segmenting merozoites in the tertian 

 organism is quite irregular in shape and contains from fifteen to twenty 

 individuals, while that of the quartan is a regular rosette in shape and 

 the merozoites average from six to twelve (Plate I., Figs. 26-28). 



JEstivo-Autumnal Type. The parasite of the restive-autumnal fever 

 develops in the blood in much the same way as the other forms, with the 

 exception that the amoeboid rings are, as a rule, smaller. The signet- 

 ring shape is more marked, and the pigment is less abundant (Plate L, 

 Figs. 31-34). Another peculiarity of this organism is that the develop- 

 ment of the larger amoeboid forms takes place chiefly in the bone marrow 

 and the spleen, while that of the tertian and quartan is to be seen in the 

 blood. Thus as soon as the plasmodium of the sestivo-autumnal type has 

 grown sufficiently to occupy about one-fourth of the red cell, it disap- 

 pears from the peripheral blood and can be found developing in the blood 

 obtained by puncture of the spleen, or in fatal cases, from the bone mar- 

 row (Plate I., Figs. 35, 36). In such preparations the mature plasmodia 

 may be found and the segmenting process followed (Plate I., Figs. 37- 

 39). The organism is not as large as the tertian, as the segmenting form 

 usually only occupies about one-half of the somewhat shrunken red cor- 



