stiates that mitosis can occur in Ijiids relatively 

 late in the differentiation process, and in the 

 erythrocyte development of the human being this 

 would be equivalent to aijout the normoblast 

 stage. 



All of the field of figure 344 was drawn as it 

 appeared under the microscope except for one 

 cell (10) and that was added from another slide. 

 Cells 9 and 10 form two stages in the thromlio- 

 cyte series. The former is the blast stage and is 

 relatively rare but is recognizable by its punctate 

 pattern of nuclear chromatin. Cell 10 is the 

 most conmionly seen early throml)ocyte and was 

 added to the drawing so that its size and colora- 

 tion could be compared with those of young 

 erythrocytes and myelocytes in the same field. 

 Its rim of dark-violet cytoplasm with a tendency 

 to stain more liglitly at the periphery is a charac- 

 teristic of the early thrombocyte (fig. 362), at 

 least as seen in bone marrow. 



Mature thromliocytes that have not disinte- 

 grated are rarely seen in smears from bone mar- 

 row for reasons already discussed. One ruptured 

 thrombocyte (cell 77) can be identified by the 

 remnant of acidophilic cytoplasm that is still at- 

 tached to it. A close study of the several naked 

 nuclei in the field reveals that some could have 

 coiue from thrombocytes init some undoubtedly 

 came from broken erythrocytes. 



When numerous fields of ])one marrow are 

 examined it is not hard to find all stages in 

 granulocytic development in the embryo, but the 

 l)one marrow of the adult, unlike that of the 

 embryo, seldom shows more than 1 or 2 early 

 stages in a single field. Only 2 stages of de- 

 velopment of the heterophil series are shown in 

 figure 34^1 — the metagranuloblast (cell 12) and 

 mature cells (13-15). A badly distorted 

 basophil (cell 16) has been labeled as a meso- 



myelocyte Ijecause it appeared to have less than 

 half the normal number of basophilic granules, 

 but in view of the disintegrating effect of aqueous 

 solutions it may be older. Cell 77 is either a 

 mature or nearly mature Ijasophil. 



In all bone-marrow smears there are smudged 

 cells, some that are slightly crushed ( cells 22- 

 25 of fig. 344) and others (cells 26 and 27) that 

 are destroyed beyond recognition. 



Lymphocytes ( cells 18—21 ) show a range from 

 medium to small but they are all mature and in 

 this particular field there is no evidence that the 

 bone marrow is a lymphocytogenic organ. A 

 better measure of this function comes from a 

 study of table 10. These mature lymphocytes 

 shown in figure 344 could have come into the 

 l)one marrow by way of the circulating blood, 

 as most of the mature ervthrocytes presumably 

 did. 



In figures 345-390 and 391-397 an attempt 

 has jjeen made to show each cell line as com- 

 pletely as possible. Obviously, many cells are 

 similar to those pictured in the circulating blood 

 and in other hematopoietic organs, but even con- 

 sidering all the cells pictured, relatively few ex- 

 amples are shown of each cell type, and no matter 

 how extensive the illustrations may be they 

 cannot su!)stitute for the actual examination of 

 slides where, in a short time, far more cells than 

 those represented in this volume can be seen. 



Three erythroblasts from bone marrow, dif- 

 fering considerably in appearance, have been 

 illustrated (figs. 34.5-347) . Two show nucleoli 

 and one does not; one has a narrow band of 

 cytoplasm and two have extensive cytoplasm. 

 The type represented l)y figure 345 is rare. Most 

 of the erythroblasts seen in adult bone marrow 

 look like figure 346 or 347. The latter with its 



Figures 378-390.— Cells of the eosinophil and basophil granulocyte series from l)one marrow of adult 

 chicken, except figure 379, which was from a day-old chick. 2,470X. 



378 Eosinophil metagranuloblast. 



379 Eosinophil mesomj-elocyte. 



380 An eosinophil mesomyelocyte more differenti- 

 ated than the preceding cell. 



381 A late eosinophil metamyelocyte. 



382, 383 Basophil promyelocytes. Figure 383 is slightly 

 more differentiated than figure 382. 



FiGtjRES 384-386; Basophil mesomyelocytes. 

 384 Early phase of the mesomj-elocyte. 



385 Mesomyelocyte with a moderate number of 

 basophilic granules. 



386 Late phase of the mesomyelocyte. 



387 Basophil metamj-elocyte. 



Figures 388-390: Basophil granulocytes from hone marrow 

 fixed in vielhyl alcohol and slained in thionin. 



388 Mesomyelocyte. 



389 Metamyelocyte. 



390 Mature basophil. 



191 



