28 TROPICAL MEDICINE AND HYGIENE 



both basic : A blue, the unaltered methylene blue, which 

 stains the ordinary cell protoplasm of actively growing 

 cells, parts of the nuclei, granules said to be basophilic in 

 some of the red corpuscles, and faintly but diffusely other 

 degenerate red corpuscles. It also stains the nuclei of 

 any red corpuscles that still possess them, and stains 

 faintly the blood platelets. 



The altered methylene blue, red in colour, but a deeper 

 red than that of eosin, has a special affinity for certain 

 substances constantly present in actively growing "cells 

 known as chromatin. In the nuclei this substance is in 

 abundance and especially concerned in processes of 

 multiplication and reproduction. 



Of the blood elements this red polychrome methylene 

 blue stains the nuclei of the leucocytes so that, as they 

 are also stained with the unaltered methylene blue, they 

 appear purple. It also stains granules present in the 

 protoplasm of some of the large mononuclear leucocytes, 

 and granules or a network in the blood platelets. 



As regards the parasites of malaria the young forms 

 with Leishman stain show a nodule of chromatin con- 

 tained in a large non-staining nucleus, a so-called " vesi- 

 cular nucleus." This vesicular nucleus is surrounded 

 by a narrow rim of protoplasm which stains blue with the 

 unaltered methylene blue. The whole forms the " ring 

 form" of the parasite and in the stained specimen, as in 

 the unstained, it is difficult to distinguish between the dif- 

 ferent species of parasites in this stage (Plate I, i, 7, 10, 16). 



The older the parasite is the more abundant the pro- 

 toplasm surrounding the vesicular nucleus becomes, as 

 growth is mainly by an increase in the protoplasm. 

 Where the protoplasm is relatively abundant the parasite 

 is not a young one. A ring form that is still small, when 

 from the relative amount of the protoplasm it is known 

 not to be young, is probably a subtertian parasite. A very 

 small ring form is also probably a subtertian, as the very 

 young subtertian parasites are smaller than either tertian 

 or quartan. 



