30 TROPICAL MEDICINE AND HYGIENE 



is more abundant but does not form a solid block, but 

 a series of coarse granules scattered about between and 

 beyond the grains of pigment (Plate I, 18, 19). The 

 chromatin in the gametocytes of all forms of malaria 

 stains only with the altered forms of methylene blue. It 

 does not stain with haematoxylin or with most basic stains 

 (Plate II). 



It is doubtful if all the parasites described here as 

 "subtertian " are of one and the same species. By some 

 of the Italian authorities they are subdivided into three 

 species, viz., pigmented quotidian, unpigmented quotidian, 

 and malignant tertian, whilst others attempt to subdivide 

 into two species only. Any classification based on the 

 periodicity of the fever with this class of parasites is 

 unreliable, as there is not a sufficient synchronicity in 

 the stages of the parasite for any marked regularity to 

 be expected. In practice one type of fever may pass 

 gradually into another type without any change in the 

 characters of the parasites found. 



In the majority of cases there are few or no pigmented 

 parasites to be found in the peripheral blood, but in these 

 cases, if fatal, the full-grown parasites found in the internal 

 organs are always pigmented. 



As regards the inquiry as to the differentiation into 

 species of the parasites having gametocytes of a sausage- 

 shape crescents we find : 



(1) That the length of cycle is very difficult to ascertain, 

 as the later stages of development are not found in the 

 peripheral blood, and that parasites of all stages may be 

 present at the same time. 



(2) That the parasites are comparatively small, but full- 

 grown parasites from less than half to two-thirds the 

 diameter of the red corpuscle are to be found in the 

 same case. 



(3) That all may be actively amoeboid, that in all the 

 pigment when first seen is finely divided, and that in all 

 in the older parasites- the pigment is coarse and black. 



(4) The number of spores varies within very wide 



