Developmental stttges found in circulating 

 blood (figs. 184-186) 



The low percentage of eosinophils in the dif- 

 ferential count makes it difficult to find develop- 

 mental stages of eosinophils in the circulating 

 blood of normal birds. The youngest observed 

 thus far is shown in figure 184 — a mesomyelocyte 

 in which there are fewer than half the number of 

 granules foinid in the mature stage. The cyto- 

 plasm is still strongly basophilic. The range in 

 coloi^ation of the specific granules is not so great 

 as has been observed in these cells in the bone 

 maiTow (fig. 379). The large size of the gran- 

 ules in the metamyelocyte (fig. 185) stands in 

 contrast to the groups of small granules in figure 

 186. These granules in figure 185 give the cell 

 an appearance similar to that of the mesomyelo- 

 cyte stage of the heterophil (fig. 374) and it is 

 possible that this cell has been misplaced, espe- 

 cially since small granules are mixed with the 

 large ones. Diiference in granule size is a char- 

 acteristic found in heterophil, but not in eosino- 

 phil, myelocytes. There is no question al)out 

 the identity of the cell in figure 186; the strongly 

 stained nucleus and the small uniform granula- 

 tions establish it as an eosinophil. 



Abnormal cells 



No cei: 

 been seen 



No cells belonging to this classification have 



Technic artifacts (fig. 187) 



This is an example of a smudged eosinophil. 

 The characteristic of a strong affinity for stain by 

 the nucleus of the eosinophil, in contrast to the 

 tendency toward defective staining in the hetero- 

 phil, is still retained in the squashed cells. The 

 scattered contents of the broken cell (fig. 187) 

 demonstrate again that the large eosinophil gran- 

 ule is composed of smaller granular units. 



BASOPHILS 



Specific granules for these cells have an affinity 

 for iiasic dyes and show metachromasia. In 



chickens this cell is more abundant than the 

 eosinophil, averaging about 2 percent in a dif- 

 ferential count. There is no confusion in term- 

 inology for this cell and basophils are homo- 

 logous through various classes of vertebrates. 

 The only confusion comes in the theoretical re- 

 lationship between the blood basophil and the 

 tissue mast cell. 



Aqueous solutions have a severe detrimental 

 effect here, as they have on heterophils; there- 

 fore, all basophils in a dried smear show technic 

 artifacts in varying degrees. This same reac- 

 tion exists in mannnalian cells and has been dis- 

 cussed by Michels ( 1938) . Because of this fact, 

 abnormal cells have not been identified. 



ISormal mature basophils (figs. 188—192) 



Basophils are only slightly smaller than 

 heterophils, as shown in the graph (fig. 197). 

 This slight difference would not be apparent 

 visually. The impression has been gained dur- 

 ing the routine examination of many slides that 

 when die technic defects are minimal the cell is 

 relatively small; whereas, when there has been 

 extensive washing out of granules the cell seems 

 larger. Not only is the size of tlie cell less but 

 even the granules are smaller when they are well 

 preserved. See, for example, figures 389 and 

 390, which show basophils from bone marrow; 

 the cells were fixed in methyl alcohol and stained 

 with thionin in alcohol. Basophils are round, as 

 are the other two granulocyte types, and they are 

 not severely deformed when other cells press 

 against them. Sometimes the cell membrane 

 becomes irregular in contour owing to the ex- 

 trusion of particles (fig. 190). 



The cytoplasm of liasophils is colorless. Usu- 

 ally it is masked by the granules jjut when they 

 are washed out there is very little residual color 

 (figs. 191 and 192). More convincing, per- 

 haps, are the small breaks seen between the gran- 

 ules when they have not been severely disturbed 

 (figs. 188 and 189). In the Petrunkevitch No. 

 2 fixed smear there is a basophilic tinge to the 

 cytoplasm (fig. 221). The spaces between the 

 granules seem larger than normal because the 

 granules are either shrunken or partially dis- 

 solved. 



The granules in the dried smear are basophilic 

 and metachromatic; that is, they have an affinity 



91 



