THE WHITE BLOOD-CORPUSCLES 919 



(6) Those staining with basic dyes basophile ; 

 (c) Those staining only with a mixture of the acid and basic dyes 

 and therefore spoken of as neutrophile. 



An acid dye is generally a salt in which the colouring-matter plays the part of 

 an acid radical. Thus eosin is the sodium salt of the coloured acid tetrabrom- 

 fluorescein. Basic dyes possess basic colour radicals. An example of this 

 class, methylene blue, is the chloride of the coloured base tetramethyldiphenthia- 

 zine. Neutral dyes, according to Ehrlich, are those in which a colour base is 

 combined with a colour acid, such as the eosinate of methylene blue, or the 

 picrate of rosaniline. 



In preparations stained with mixtures of these dyes we may 

 distinguish the following types : 



(1) The polymorphonuclear cells. These present a lobed nucleus, 

 and their protoplasm contains abundant fine neutrophile granules. 

 They form about 70 per cent, of the total leucocytes. If the specimen 

 be overstained with eosin the granules may take on a red stain. 



(la) A few cells are sometimes seen with a horseshoe or hour-glass 

 nucleus and presenting a few neutrophile granules. These are spoken 

 of as transitional cells, and have been supposed to represent an inter- 

 mediate stage between large mononuclear or hyaline cells and the 

 polymorphonuclear leucocyte. They do not form more than 1 per 

 cent, of the leucocytes. 



(2) The lymphocytes are small cells with a round nucleus sur- 

 rounded by a thin layer of hyaline protoplasm which is free from 

 granules. These form 23 per cent, of the leucocytes. 



(3) Large mononuclear or hyaline corpuscles. These cells are two 

 or three times the size of a red corpuscle, and possess a large oval 

 nucleus which stains feebly with basic dyes. In normal blood not 

 more than 2 per cent, of the leucocytes are of this type. 



(4) In every well-stained blood-film the eosinophile corpuscle is 

 very evident, although not forming more than 3 per cent, of the white 

 corpuscles. The nucleus is generally single, but is often crescent- 

 shaped or reniform. The protoplasm is crammed with large discrete 

 highly refractive granules which stain deeply with eosin and give 

 micro-chemical reactions for iron as well as phosphorus. The granules, 

 which in man, dog, and rabbit are spherical, are cuboidal in the horse, 

 and in birds have the shape of short rods. 



(5) A cell which is found with difficulty, but is apparently a normal 

 constituent of human blood, is the basophile leucocyte. This, which 

 is somewhat smaller than the polymorphonuclear cell, has a lobed or 

 tri-lobed nucleus and presents a number of granules in its protoplasm 

 which stain deeply with basic dyes. It is sometimes spoken of as a 

 ' Mast ' cell, the German term for the cell being used without transla- 

 tion. It does not form more than 0-5 per cent, of the total leucocytes 



