456 THE BLOOD [CH. XXIX. 



The Colourless Corpuscles. The white or colourless corpuscles 

 "are masses of nucleated protoplasm ; they are nearly spherical when 

 at rest, but owing to their amoeboid movements (see p. 11) exhibit 

 considerable changes in outline when they are active, as they are at 

 body temperature. 



In health, the proportion of white to red corpuscles is on the 

 average 1 to 500 or 600, but this varies considerably even in the 

 course of the same day. The number of lymphocytes is greatly 

 increased by a meal. Also, in young persons, after haemorrhage and 

 during pregnancy, there is a larger proportion of colourless blood - 

 corpuscles ; in old age they are diminished. 



Several varieties of colourless corpuscles are found in human 

 blood. They are represented in the accompanying coloured plate, 

 stained by different methods ; the column on the left shows their 

 appearances as stained by a mixture of eosin and methylene blue 

 (Jenner's stain). The middle column shows them as stained by 

 Ehrlich's triacid dye (acid fuchsin, methyl-green, and orange G-). 

 In the right-hand column, the cells were stained with a mixture of 

 haematoxylin and eosin. The following are the varieties shown : 



(a) Lymphocytes. These are only a little larger than red 

 corpuscles. The nucleus is relatively large, and usually round ; the 

 protoplasm around it forms quite a narrow zone. The nucleus, as is 

 the case with all nuclei, is basophile, and stains with such basic dyes 

 as methylene blue. The protoplasm presents no distinct granules 

 and is also basophile. The lymphocytes comprise about 25 per cent, 

 of the total colourless corpuscles. 



(b) Large mononuclear leucocytes. A relatively small oval nucleus 

 lies near the centre of basophile protoplasm, which again presents no 

 definite granulation. Their diameter is 12-20 /*, and they form only 



1 per cent, of the total colourless corpuscles. 



(c) Transitional leucocytes. The cell-body is somewhat smaller 

 and is mainly basophile. A certain amount of neutrophile granula- 

 tion may be seen. The strongly basophile nucleus may present all 

 gradations between an oval and lobed condition. In normal blood 

 their number is variable, but, as a rule, they only make up about 



2 to 4 per cent, of the total colourless corpuscles. They are called 

 transitional on the hypothesis that they represent an intermediate 

 condition between the large mononuclear leucocytes and the poly- 

 nuclear leucocytes described under d. It is, however, doubtful if 

 this hypothesis is correct, and some histologists think the b and c 

 varieties originate from the endothelial wall. 



(d) Polynuclear leucocytes. These are 9-12 /UL in diameter, and 

 form the main mass of the colourless corpuscles (70 per cent.). 

 They have several nuclei, which are strongly basophile and present 

 many different shapes, and are usually connected by threads of 



