1910.] Till': BLOOD OF GROUSE. 723 



tliese sets of ol)sei'vatiori.s there are wide cli.scre[)ancies between 

 the results obtained by different investigatoi-s, and much con- 

 fusion has arisen thei'efrom. 



The difierent I'esults obtained by various investigators are 

 partly explicable, for the constitution of the blood of birds may 

 vary among individuals of the same species. Also there are 

 differences due to age and sex, while the conditions under which 

 the investigations are made have some influence on the result. 



The chief difficulties of manipulation for the investigation of 

 the blood of such birds as grouse are the rapidity with which 

 coagulation occurs, and the rapid alteration and disintegration 

 that often follows the death of the blood elements. The great 

 rapidity of the onset of degeneration in the leucocytes is such 

 that extreme accuracy in counts of these cellular elements is not 

 easily obtained, and the numbers of erythrocytes and leucocytes 

 found in different series of counts consequently bear a varying 

 relation one to another in apparently normal birds, even when 

 the factors noted in the preceding paragraph have been con- 

 sidered. Nevertheless, the correlation of the numbers and 

 condition of the blood-elements, particularly of the leucocytes, 

 with the occurrence of specific protozoal and lielminthic parasites, 

 renders an examination of the blood a most useful adjunct in 

 investigating somewhat obscure diseases. Several protozoal para- 

 sites [see Fantham (1910)] are present in grouse, both in the 

 blood and in the gut, and the condition of the bird's blood 

 can be correlated with the presence of some of the individual 

 parasites. 



II. Methods. 



Blood taken from a wing vein was used in the case of living 

 birds, of which twelve were thus examined. In the case of freshly 

 killed grouse, blood taken directly from the heart was employed. 

 The usual methods and pi"ecautions were followed in securing 

 suitable drops of blood for examination. 



Hayem's fluid was used as a diluent for counting the red cells 

 of the blood, while Toison's fluid was used in the case of the 

 leucocytes. 



The Thoma-Zeiss h»mocytometei' was employed. The disc of 

 the counting chamber was ruled according to Zappert. 



A dilution of at least 200 or 250 wa,s found to be necessary 

 for counting the red cells, and a dilution of 20 to 25 was a))solutely 

 necessary in counting the leucocytes. Sometimes a dilution of 

 100 was taken in counting the leucocytes, and this greater 

 dilution was often preferable. 



For differential leucocyte counts blood smears were made on 

 both cover-slij)S and slides, especially the former. 



The stain generally used in making pi'eparationsfor differential 

 coiuiting was that of Jenner. Occa.sionally Giem.sa's stain was 

 employed. 



