lire 82 the cytosome is frothy and contains two 

 irregularly shaped masses of specific granular 

 material, and in figure 83 the entire cytoplasm 

 has a pinkish color, and abundant specific ma- 

 terial surrounds the vacuoles. Figure 84 shows 

 the specific substance scattered in clusters and 

 clumps throughout the cytosome, and the cyto- 

 plasm itself has a pinkish color. Tlie cell (fig. 

 81) is probably least removed from the normal 

 in that it is not uncommon to find thrombocytes 

 with four clusters of specific granules (figs. 88, 

 p-s). 



When cells of the type exemplified by these 

 figures were first observed, it was assumed that 

 because the cells were large and tended to have 

 a rounded shape, they were immature; but after 

 die developmental series had been worked out 

 jjoth in the embryo and in the adult, and it had 

 been repeatedly demonstrated that the specific 

 granules of thrombocytes come relatively late in 

 the developmental process and that when they 

 appear only 1 or 2 small granules are present, it 

 was concluded that the overproduction of such 

 granules must have some other explanation. Be- 

 cause they often occurred in birds suspected of 

 being in ill health or known to have been inocu- 

 lated with tumor transplants, they have been 

 called reactive thrombocytes. 



A second type of abnormal cell, the degenerat- 

 ing thrombocyte (figs. 85-87), is very common. 

 As previously stated, degeneration is part of the 

 normal function of the thrombocyte; yet degen- 

 eration from the standpoint of the individual cell 

 can hardly be considered normal. Death and 

 the processes leading up to it are not normal for 

 the individual; yet from the standpoint of the 

 race and the replacement by successive genera- 

 tions, death must be considered as normal. 



Clotting of the blood of birds proceeds at about 

 the same rate as in mammals (Dorst and Mills, 

 1923) . When smears are made, however, there 

 is not as rapid clumping of throml30cytes as there 

 is of platelets, and cytologic changes can be fol- 

 lowed in more detail in avian cells than in tlie 

 latter. The first reaction involves a sliift in 

 staining color (fig. 85) of the cell membrane from 

 a pale blue to a reddish violet or reddish orange. 

 Whether this is brought about by a condensation 

 of cell substance or by shrinkage beginning at the 

 cell surface has never been determined. Diesem 

 (1956) has illustrated this affinity of the throm- 

 bocyte margin for eosin in his plate 1. His 



figure is similar to that shown in our figure 85. 

 Usually the accentuation of the edge of the cell 

 is accompanied by a shift in cell and nuclear 

 sliape from an oval to a more rounded condition. 

 More often the perimeter of the cytosome breaks 

 away from the cell and there remains only a rela- 

 tively narrow rim of cytoplasm drawn out into 

 irregular peaks (figs. 86 and 87) . In both these 

 illustrations, specific granules served to identify 

 the cell type, but again there is considerable sim- 

 ilarity to a lymphocyte. This is especially true 

 when the specific granules are absent, as is usu- 

 ally the case in dn-ombocytes reaching this stage 

 of degeneration. When the thrombocyte is small 

 like figure 87, the possilnlity of confusion is not 

 very great because this shrunken pyknotic cell is 

 smaller than even a small lymphocyte, but a large 

 thrombocyte with a nucleus of corresponding 

 magnitude can often raise a question of how it 

 should be classified. 



The rate at which the thrombocyte arrives at 

 this terminal stage of degeneration is variable, 

 and the predisposing factors are known only in 

 part. It has been observed that usually a smear 

 inade within a few seconds after pricking the 

 wing vein will give well-preserved thrombocytes, 

 evenly distributed ; but with some birds, even a 

 few seconds of delay, such as occurs in taking 

 the second drop of blood instead of the first, will 

 produce many cells showing early reactions sim- 

 ilar to figure 85. The taking of the first drop 

 is contraindicated for good smears in mammals 

 l)ut has been found by experience to give the laest 

 result in birds. On the other hand, in some 

 chickens one may be quite careless, even allow- 

 ing a pool of blood to accumulate on the feathers, 

 and after waiting 20 to 45 seconds before making 

 the smear one may yet obtain thrombocytes that 

 are well preserved. Even a 2-minute delay may 

 not cause much more degeneration than may be 

 found in certain birds from which the blood is 

 taken immediately. 



Technic artifacts 



No figures have been made because nodiing 

 lias been found that could be so classified ah 

 though it is most probable that it does occur. 

 Just as there are many smudged erythrocytes, 

 there are proljably smudged thrombocytes. A 

 partially smudged thrombocyte would resemlde 



46 



