nucleus and (2) light-staining orange spheres 

 (figs. 370-372). In figure 370 only vacuoles 

 are present in the cytosome but in figure 371 some 

 vacuoles are filled with lightly stained orange 

 spheres, and in figure 372 one or two of these 

 spheres have taken on the dark-orange color that 

 places them at the transition where the specific 

 bodies make their appearance. Because the 

 stages antecedent to specific granule production 

 can be followed so readily in birds, it seems that 

 use of avian blood would be advantageous in 

 further study of the early stages of granulopoie- 

 sis. The magenta rings and the granules vary in 

 number; in some cells there are but few and in 

 others they are abundant. The nature of the 

 stainable material inside the magneta ring is not 

 known. 



The small granules are of two types; one takes 

 a magenta stain and the other, a deep orange. 

 If figures 370 and 372 are compared, it will be 

 noted that in the latter the magenta-stained 

 granules are scattered around the orange-stained 

 spheres and not in them ; but in figure 371 many 

 of the orange granules lie in the exact center of 

 each sphere and others do not. These orange 

 granules are abimdant in figure 374. The ques- 

 tion has come to mind repeatedly, Are the orange 

 granules identical with the central bodies of the 

 mature heterophil granulocyte? It might seem 

 that this should be easy to determine by following 

 the development of the rods to see where the 

 granules go, but the presence or absence of a cen- 

 tral body in the rods is not constant, as was seen 

 in figures 154-165, and not a single rod in 

 figures 373—377 shows a central body inside it. 

 In figure 372 the small granules lie at the pe- 

 rijihery of the orange spheres. 



It was the opinion of Dantschakoff (1908b) 

 that there was metachromasia of the specific 

 granules of heterophils during the early stages of 

 differentiation. This reaction would agree with 

 the observations reported in the paragraph above, 

 to the extent that the first granules to appear are 

 of two types, magenta-staining and pale orange- 

 staining. The magenta rings appear to be a dif- 

 ferent organelle than the magenta granules and 

 were not observed by Dantschakoff in her sec- 

 tioned material. In a study by Lucas and Den- 

 ington (1956, unpublished data) magenta rings 

 were observed in sectioned material. 



The nucleus of the promyelocyte may be dis- 

 tinct but often it appears as in figures 371 and 



372, where nuclear boundaries are vague, and at 

 tliis stage they appear the same as they do in the 

 embryo spleen." 



Several steps are involved in the production of 

 a rod. First a vacuole is formed, it is occupied 

 by a light-orange sphere, which progresses to a 

 darkly stained orange sphere, and this in turn be- 

 comes a rod. The development of a sphere and 

 its transformation into a rod mark the beginning 

 of tlie mesomyelocyte stage (figs. 373 and 374). 



The mesomyelocyte stage has a nucleus that 

 may be large and indefinite (fig. 373) or small 

 with definite chromatin clumps (fig. 374) . Also, 

 some magenta rings and granules may persist 

 (fig. 373) . The process of rod differentiation is 

 more advanced in figure 373 than in 374; in the 

 latter it is not much farther than the "dark- 

 orange sphere" stage. When the rods form 



' One clinical hematologist, after seeing colored reproduc- 

 tions of these avian myelocytes, said: 



"The myelocytic series may be drawn exactly as they ap- 

 peared, but if that is true, they appear to be inadequately 

 stained. If we had a human bone marrow or blood smear that 

 had nuclei which were as pale and the structures as ill defined 

 as painted, we would say that the stain was unsatisfactory, 

 would not attempt a differential or diagnosis and would ask 

 for better stained preparations or a restain of the same prep- 

 aration. A combination of Giemsa as a counterstain for the 

 Wright's or a change of the buffer water or a longer staining 

 time might give better results." 



Various technics, including Wright-Giemsa, have been tried, 

 and although differences in the appearance of the cells may 

 occur — with the same or different technics — the general picture 

 of heterophil granulopoiesis as shown here is representative 

 for the normal chicken. Nothing has been seen that supports 

 the idea that avian myelocytes look the way they do in im- 

 pression smears because inappropriate technics were chosen or 

 because appropriate technics were faultily applied. It is sug- 

 gested that the promyelocytes often appear the way they do 

 because the cell undergoes extensive hypertrophy, both of the 

 nucleus and cytosome, as one of the first steps in heterophil 

 myelopoiesis and because the firm vacuoles and the liglit- 

 orange bodies give a honeycomb appearance to the nucleus and 

 cytosome by puncturing these structures at the time the cell is 

 flattened in the process of making the smear (fig. 371). 



A little later in development, nuclear detail becomes visible 

 again I fig. 374). In the interim the nucleus has not changed 

 its appearance to any great extent (compare figs. 369 and 374). 

 Therefore, not much has been lost by using a technic (May- 

 Griinwald Giemsa) that does not reveal all the details of the 

 nucleus at the promyelocyte stage. On the credit side, this 

 stain reveals the subtleties of changing form and color in the 

 rod precursors, which seems important when studying granu- 

 locyte development. When Petrunkevitch's No. 2 was used 

 on spleen myelocytes, followed by May-Griinwald Giemsa, the 

 border of the nucleus could be traced readily, and the nucleus 

 appeared as a large body containing a delicate granulation, 

 but the cytoplasmic inclusions suffered severely by this technic. 



The author of the paragraph quoted is not mentioned here 

 by name for the reason that it is not intended to make this 

 volume a springboard for a controversy. He is respected as 

 an outstanding clinical hematologist of human blood and he 

 may be expressing an opinion that would be shared by all 

 hematologists of mammalian blood who look at these illustra- 

 tions. A common ground of understanding is, of course, neces- 

 sary for any discussion and this can be reached more quickly 

 when it is recognized that many details of human and avian 

 blood are not the same. 



195 



