262 CLINICAL BACTERIOLOGY AND H^MATOLOGY 



DIFFERENTIAL LEUCOCYTE COUNT 



The following varieties of leucocytes are to be recognized, 

 the description in each case being taken from a preparation 

 stained by Jenner's method. 



A. CELLS DEVOID OF GRANULES. 



i. Lymphocytes (Plate VIL, Figs, i, 2, 3, 4) are variable in 

 size, some being about as big as a red corpuscle, others nearly 

 twice this size. Each has a single nucleus, which -is circular 

 or nearly so, and which stains a deep blue. The protoplasm 

 forms a narrow band round the nucleus, and also stains blue, 

 often more deeply than the nucleus. 



Variations of these cells occur. In some cases the whole 

 seems to stain uniformly, in which case it is probably a free 

 nucleus (Plate VII., Fig. 3). In others the protoplasm ap- 

 pears to be studded with blue granules, which often lead 

 beginners astray. They are not true granules, but knots in 

 the protoplasmic network.* 



In healthy adults they average about 25 per cent, of all the 

 leucocytes present, varying between 22 and 28 per cent. In 

 childhood they are more numerous up to 60 per cent. 



The small forms are the more numerous, but as no trust- 

 worthy diagnostic information can be drawn from the pro- 

 portions of the large and small forms, they are usually 

 counted together. Very large forms are often abundant in 

 acute lymphatic leucocythsemia. 



Large Hyaline or Large Mono-nuclear Leucocytes (Plate 

 VII., Figs. 5, 6). These are the largest cells met with in 

 normal blood, and may have a diameter two and a half that of 

 a red corpuscle. They have a round, oval, kidney-shaped, or 

 twisted nucleus, which stains less deeply than those of the 

 lymphocytes, and has often a purplish colour. The protoplasm 

 is relatively more abundant than in the lymphocytes, and stains 

 very faintly of a bluish or purplish colour. It often has false 

 granules similar to those of lymphocytes, but no true ones. 



It occurs in small numbers (i to 4 per cent), and variations 

 are of little diagnostic importance. 



* More modern methods show that true granules occur in these cells. 

 They are not of diagnostic importance. 



