FREQUENCY of LENGTH and WIDTH of THROMBOCYTES 



- lOidi-l) 



° ■ 3 ' 4 5 6 7 5 



LENGTH and WIDTH m MICRONS 

 Figure 89.-Frequency distribution curves for length and widtli of 90 normal thrombocytes. 



larger than that of the lymphocyte figure 102, 

 and if it were not for a few faint specific gran- 

 ules it would be classed as a lymphocyte. The 

 cytoplasm does not always contain spaces or 

 vacuoles; instead, its texture and coloration 

 sometimes may be indistinguishable from that 

 of lymphocytes. Fortunately the specific orange 

 granules are very constant in their occurrence if 

 not in their number and arrangement. 



Developmental stages found in circulating 

 blood (figs. 75-79) 



Developmental stages for the dirombocytes 

 were first worked out from the circulating blood 

 of the embryo incubated for about 4 days and 

 then in older embryos. These obsei-vations pro- 

 vided clues for recognition of thrombocyto- 

 genesis in bone marrow and it was only follow- 

 ing this that they were recognized in the circulat- 

 ing blood of the hatched chicken. Developmental 

 stages represented by figures 75-79 were found 

 in 1 specimen 6 days posthatching. At this 

 early age the probability of discovering develop- 



mental stages is greater that at older ages, just 

 as immature erythrocytes are more abundant 

 soon after hatching than they are later. 



There are about 75 red cells to one throm- 

 bocyte; therefore, considerable more searchmg 

 is necessary to find innnature thrombocytes than 

 corresponding stages of the erythrocyte series. 

 None were found that were younger than about 

 the middle of the developmental process (figs. 

 75-77), which is approximately equivalent to 

 cells (figs. 288-290) found in tlie circulating 

 blood of an embryo incubated 4 days, or (fig. 

 363) from adult bone marrow. The nucleus 

 is still large relative to the cj^osome, but at 

 this mid-stage of immaturity the cytosome has 

 more area than merely a narrow rim of in- 

 tensely stained basophilic material as it had at 

 the thromboblast stage. By the mid-immature 

 stage, the cytoplasm has lost some of its baso- 

 philia and has become vacuolated. The vacu- 

 oles tend also to lighten the staining. Specific 

 granulation may (figs. 76 and 77) or may not 

 (fig. 75) be evident. The nuclear pattern is 

 intermediate between the punctate reticulum of 

 the blast stage and the closely packed, dense 



44 



