310 THE GROUSE IN HEALTH AND IN DISEASE 



possess a well-marked oval nucleus, centrally placed. The erythrocytes of Grouse 

 Er^jj. are about 11 "5^ to 12// long by 7^ to 7'5^ broad. In fresh preparations 

 rooytes. ^-^e cytoplasm of the red cells of healthy Grouse is practically homogeneous, 

 •or but very faintly granular. Stained preparations give the same results. It is 

 rare for large granules, chromatoid granules, or vacuolations to_^ be present in the 

 red cells of healthy birds. The nucleus stains deeply, and shows a well-marked 

 chromatic meshwork with small net-knots upon it at intervals. 



The red cells of various birds are much the same. There may be slight differ- 

 ences in size and shape. In Figs. 2 and 3 are depicted stained specimens of the 

 red cells of the pigeon and fowl respectively, from which it will be seen that the 

 erythrocytes of the pigeon are slightly narrower than those of the Grouse and fowl, 

 and somewhat less rounded at the ends. 



The number of red cells of Grouse varied from 3,600,000 to 5,800,000 per 

 cubic millimetre, averaging 4,300,000 per cmm. These figures result from blood- 

 counts of fifty birds. 



The number of red cells is apparently higher in cock Grouse {e.g., 4,400,000 

 per cmm.) than in hen Grouse {e.g., 3,800,000 per cmm.). 



(6) Leucocytes. — The leucocytes of Grouse are a subject of much intrinsic 



difiiculty, and it is impossible to consider the grouping arrangement given below as 



more than provisional. The classification of the leucocytes of birds can 



Leucocytes. 



be placed on a really sound basis only when detailed knowledge of the 

 development of all the elements of the blood of birds has been obtained. In spite 

 of good work by Denys, Dantschakofi", and others, such a complete developmental 

 investigation of the blood of birds is still wanting. Owing both to the lack of time 

 at my disposal, and to the great scarcity of quite fresh material, I am unable to 

 attempt such an investigation, and therefore have availed myself of the classifica- 

 tion at present adopted by such authorities as Burnett (1908), modifying their 

 statements in accordance with my own personal observation and adding a number 

 of details hitherto overlooked. 



1. Lymphocytes (PI. xlv., Figs. 5, G). — The lymphocytes are the smallest of 

 the leucocytes. They are from 5'5/x to 8^ in diameter approximately. They are 

 Ly„,. smaller than the average red corpuscles. Each lymphocyte possesses a 



J) locy es. -well-marked round or oval nucleus which is relatively large and occupies 

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

 phile, and is reduced to a rim around the nucleus. The lymphocytes have a great 

 tendency to collect together in groups on blood-smears, and in such aggregations 



