Venzlaff (1911) made erythrocyte counts from 

 45 species of birds. In collecting his material 

 he attempted to obtain a reasonably uniform 

 representation of most of the families of birds — 

 from the Struthioniformes to the Passeriformes. 

 Body weight and size of the erythrocytes were 

 given, also, but the interrelationship of these 

 variables is still open to question. 



Percentage values are often misleading — ^the 

 real differences between sexes are seen more 

 clearly in the data giving the number of cells per 

 cubic millimeter (table 17). The Rhode 

 Island Reds had a high thrombocyte count, 

 and a slightly elevated total white-cell count in 

 comparison with the others. The monocytes of 

 both farm stocks were low both in aljsolute and 

 in percentage values. This may be the reason 

 why some investigators group monocytes with 

 lymphocytes in their differential counts. Hetero- 

 phils were even more variable than lymphocytes, 

 ranging from 10 percent to 25 percent, and on 

 the basis of absolute numbers per cubic milli- 

 meter, the differences are even greater — 2,900 

 to 12,600 — over a fourfold difference. The 

 range in average number for the lymphocyte 

 groups was slightly over twofold. 



The low heterophil count for our birds may 

 be due to the fact that these chickens are held 

 indoors throughout their lives and are relatively 

 free from parasites and common poultry in- 

 fections except lymphomatosis. The count was 

 the highest for Rhode Island Reds, yet in all 

 groups of chickens it was definitely less than in 

 wild birds (tables 18, 19, 20, and 21) . In fact 

 there are several points of difference between 

 the percentage values of leukocyte types in 

 chickens and wild birds, the most striking being 

 the low value for lymphocytes, the high value 

 for heterophils, and a consistently high level for 

 monocytes. Eosinophils in the Canada goose 

 and the mallard duck ran 7 percent and in pigeon 

 and pheasant the averages were low. Basophils 

 ranged from 2 to 10 percent. Any comparison 

 of these tables with the data on the chicken indi- 

 cates that absolute values have greater usefulness 

 than percentage values, and any extensive studies 

 on comparative avian hematology should include 

 data on the actual number of cells per cubic 

 millimeter. 



The values on counts made by Wickware 

 (1947) should be compared with those given in 

 table 17 for the leukocyte types. About the 



only generalization that can be made is that these 

 data further emphasize that there is high varia- 

 bility among different groups of chickens. 



Cell counts on pigeons, more extensive than 

 given here (table 21), were made by DeEds 

 (1927). He found a very high variability for 

 the counts of each cell type; for example, small 

 lymphocytes varied from 5 to 53 percent, large 

 lymphocytes from 9 to 67 percent, heterophils 

 from to 25 percent and the remaining cell types 

 showed a similar variability. Thrombocytes 

 varied from 8,000 to 89,000 per mm.' 



Less variability was experienced in a later 

 study on pigeon blood cells by Schoger (1939). 

 In his data, lymphocytes varied from 40.5 to 

 62.0 percent, monocytes from 4.0 to 6.5 percent, 

 heterophils from 29.0 to 48.5 percent, eosino- 

 phils from 2 to 4 percent, and basophils from 

 0.5 to 2.0 percent. He used 16 mature, healthy 

 birds. The variability in his data was less than 

 shown in table 21. Red cell counts, hemo- 

 globin, and differential counts for leukocytes 

 were made by Gauger et al. (1940) on normal 

 pigeons and on pigeons infected with para- 

 typhoid. Their counts on both normal and in- 

 fected birds were also highly variable. They 

 concluded that, due to this variability, chronic 

 carriers of this pathogen could not be dis- 

 tinguislied from noninfected pigeons by blood- 

 cell counts. 



The values given by Hewitt (1942) of dif- 

 ferential counts on laboratory ducks (breed not 

 given) agree closely with our averages in table 

 18, based on common mallards. Hewitt's aver- 

 ages were: Lymphocytes, 40.4 percent; mono- 

 cytes, 5.3 percent; heterophils, 44.4 percent; 

 eosinophils, 7.1 percent; and basophils, 2.4 per- 

 cent. Normal differential blood counts for tur- 

 keys, as given by Johnson and Lange (1939), 

 are: Lymphocytes, 50.6 percent; monocytes, 1.9 

 percent; heterophils, 43.4 percent; eosinophils, 

 0.9 percent; and basophils, 3.2 percent. Mc- 

 Guire and Cavett (1952) gave the counts for 

 normal values of turkey blood in cells per mm.' 

 as follows: Total leukocytes, 38,700; lympho- 

 cytes, 17,200; monocytes, 1,900; heterophils, 

 16,600; eosinophils, 40; and basophils, 1,700. 

 These data give essentially the same percentage 

 values as obtained by Johnson and Lange. A re- 

 view of earlier literature on blood values for 

 ducks is given by Magath and Higgins (1934). 

 They also determined for other anseriform spe- 



219 



