1910.] THE BLOOD OF OUOUSE, 725 



an investigation, and tlierefoi-e liave availed myself of the 

 classification at pi'esent adopted by such authorities as Bui-nett 

 (1908), modifying their statements in accordance with my own 

 personal observation and adding a number of details hitherto 

 overlooked. 



1. Lymphocytes (PI. LXIII. figs, 5, 6). — The lymphocytes are 

 the smallest of the leucocytes. They are from 5*5 // to 8 /n in 

 diameter approximately. They aie smaller than the average red 

 corpuscles. Each lymphocyte possesses a well-marked round or 

 oval nucleus which is I'elatively lai'ge and occupies most of the 

 cell. The cytoplasm of the lymphocyte is small in amount, is 

 basophile, and is reduced to a rim around the nucleus. The 

 lymphocytes have a great tendency to collect together in gi-oups 

 on blood-smears, and in such aggregations the cytoplasm of the 

 niembei'S away from the periphery of the group is I'cduced to a 

 minimum. 



The lymphocytes are sometimes subdivided into laige and 

 small varieties. The larger specimens of lymphocytes gradually 

 merge into the small mononuclears, a.nd the naming and classi- 

 fying of such leucocytes is often a matter of personal ojiinion. 



2. Large Monoivaclear Leucocytes (Hyaline cells). — These are 

 large, approximately circular cells avei'aging 9 /x to 11 5 ju in 

 diameter (PI. LXIII. figs. 7, 8). In a film stained with Giemsa's 

 fluid the mononucleai' leucocj'tes are easily distinguishal)le not 

 only from their lai'ge size but also from the fact that their cyto- 

 plasm stains a vivid blue and the nucleus a beautiful purple. 

 The general cytoplasm of the cell is almost homogeneous in 

 character. 



The niicleus of a mononuclear leucocyte of grouse is large, 

 occupying about half of the cell, and is often round or oval 

 (tigs. 5, 6). At other times the nucleus is somewhat curved 

 or indented (fig. 8). The chromatin of the nucleus takes the 

 form of a fairly dense mass, exhibiting in stained specimens a 

 uniformly mottled appearance ; it is situated to one side of the 

 cell. 



With Jenner's stain the nucleus colours a rather deep blue, 

 while the cytoplasm stains only a faint blue and so is slightly 

 basophile. 



As Burnett (1908, p. 35) writes: "One can find all stages 

 between typical lymphocytes with a small amount of strongly 

 basophile, coarsely reticular cytoplasm and typical large mono- 

 nuclears with a much larger amount of faintly baso^jhile, finely 

 I'eticular cytoplasm." 



3. rolyinorphonuclear leucocytes {BMVuett) oi- Crystalloid eosino- 

 phile cells (Cullen, Warthin). — The apparently polymorphonviclear 

 leucocytes of birds exhibit marked difterences fiom those of 

 manimals as I'egards the contained granules. 



These cells in grouse are round, as seen in stained preparations, 

 anil measure from 9 ^ to 9'5 ju in diameter (figs. 10-12). The 



