heterophils and eosinophils of ducks and tur- 

 keys. CuUen (1903) noted that in guinea hens 

 and in kingfishers the percentage of heterophils 

 was lower than for eosinophils, a relationship 

 that was the reverse of that found for other 

 species of birds, therefore, close attention was 

 given to these cells in the blood of wild birds and 

 it was readily apparent that the confusion arose 

 from the fact tliat heterophils and eosinophils are 

 highly variable in their appearance; some heter- 

 ophils resemble eosinophils and some eosinophils 

 resemble heterophils. Confusion has been cre- 

 ated by the fact that in some species — the duck, 

 for example — the eosinophils are often rare, and 

 it may be that, in making differential counts, cer- 

 tain variants of the heterophils were classified as 

 eosinophils and the remainder as heterophils. 



Figure 400 is a heterophil from a mallard 

 duck taken in Michigan and figure 401 is from an 

 individual of the same species taken in Utah. 

 It should not be assumed that the cytologic dif- 

 ferences are due to geographic habitat; this much 

 variation can be found in a group of slides from 

 a species within a particular locality. One of 

 these cells (fig. 400) has broad, short, rounded 

 rods that look much like large eosinophil spheres 

 (compare with fig. 404) . The rods of figure 400 

 are not uniformly stained. The density of 

 staining is greater toward the edge of the rod 

 tlian toward the center. The clear area of the 

 center is not sharply defined like the vacuole in 

 the center of the rod in chicken blood (fig. 166) . 



The rods in another specimen of mallard duck 

 were small, narrow, and tapering with pointed 

 ends (fig. 401). It is this shape that is charac- 

 teristic of heterophil rods in most birds. In the 

 specimen from which the heterophil (fig. 401) 



was taken, the eosinophils, of which figure 402 

 is an example, looks somewhat like heterophils. 

 This similiarity in appearance is a possible cause 

 of confusion. 



The two types of specific inclusions are not 

 actually alike when examined under high magni- 

 fication. The specific eosinophilic granules are 

 composed of very small bodies that appear to lie 

 on a network. If the granules merge with the 

 network, because they are small or because there 

 is no color difference between tlie two, the net- 

 work may then simulate a mass of poorly pre- 

 served rods in a heterophil. 



Wright's stain, when applied to chicken blood, 

 often incompletely colors the chromatin of the 

 heterophil nucleus. Heterophils of many other 

 species show the same artifact. The difference 

 in staining affinity between the nuclei of heter- 

 ophils and eosinophils has been utilized to aid 

 in distinguishing the two cell types, and a search 

 for tliis difference is always made at the begin- 

 ning of a study on blood from a species not pre- 

 viously examined. 



Incomplete nuclear staining of heterophils is 

 shown in figures 400, 401, and 403, and complete 

 nuclear staining of eosinophils in figures 402, 

 405, and 407. 



When a specimen is found where the hetero- 

 phil nucleus stains as well as the eosinophil 

 nucleus, considerable study may be required 

 before the two cell types can be distinguished 

 readily. Hewitt (1942) faced the same prob- 

 lem in the selection of proper terms for hetero- 

 phils and eosinophils. Eosinophils with round 

 granules occurred only in bone marrow. There- 

 fore, without attempting to solve the homologies 

 of heterophils and eosinophils in ducks with those 



Figures 400-410. — Granulocytes from ducks and turkeys. 2,470 X. 



Figures 400, 401: Heterophils from adult male mallard 

 ducks. Wright's stain. 



400 From Lowell, Mich. 



401 From Utah. 



402 Eosinophil from same slide as preceding one. 



Figures 406-408: Granulocytes from the turkey. Wright's 

 stain. 



406 Heterophil. 



407 Eosinophil from same shde as preceding one. 



408 Basophil. 



Figures 403, 404: Two granulocytes adjacent to each other. 

 From a baldpate drake. Wright's stain. 



403 Heterophil. 



404 Eosinophil. 



405 Eosinophil. Ruddy duck. 

 Griinwald Giemsa. 



Juvenile male. May- 



Figures 409, 410: Turkey granulocytes from a smear fixed 

 in Petrunkevitch No. 2 and stained with May-Grunwald 

 Giemsa. Same bird as the one from which figures 406 and 

 407 were taken. 



409 Heterophil. 



410 Eosinophil. 



207 



