chromatin clumps of the fully mature cell. The 

 areas occupied by liniu network and basichro- 

 matin are about equal. 



The late innnature stage (figs. 78 and 79) 

 shows certain changes from the pi'eceding phase. 

 The cell has usually attained a slightly oval shape 

 but this is not always the case (fig. 364 from bone 

 marrow) ; the cytoplasm has nearly the same 

 degree of coloration found in the mature cell and 

 it shows extensive vacuolization; the nucleus may 

 still have a round contour or may be slightly oval, 

 but more important is the increased density of 

 chromatin clumping. Specific granulation is 

 present, but a point to which reference will be 

 made later is the faintness of the granules and 

 the fact that there is seldom more than 1 or 2 

 small granules present. 



Abnormal cells (figs. 80—87) 



Probably neither of the two types of cells in- 

 cluded under this heading could be called patho- 

 logical. The cells in the first group have been 

 classified as reactive cells (figs. 80-84) and 

 those in the second group illustrate the cellular 

 breakdown that begins as soon as the blood is 

 liberated from the body (figs. 85-87). The 

 latter might even be classed as a technic artifact 

 because it takes place outside the body. Clot- 

 ting, on the other hand, also takes place outside 

 the body and yet is a normal function of blood, 

 but from the point of view of cytology this proc- 

 ess is degeneration. 



The type of cell shown in figures 80-84 is 

 often seen in blood smears from birds that have 

 been inoculated with lymphoid tumor cells or 

 filtrate, and occasionally it will be found in large 

 numbers in seemingly normal birds. All the ex- 

 amples selected for illustration were taken from 

 apparently normal birds, but the chicken that 

 furnished the cell for figure 84 died with exten- 

 sive neural lymphomatosis 44 days after the 

 smear was taken. A 5-week-old chicken fur- 

 nished the material for figures 80, 82, and 83, 

 and in the same slide there were an unusual num- 

 ber of smudged monocytes of which figure 149 is 

 an example. Not enough has been done to use 

 the blood picture as an indicator of incipient 

 lymphomatosis. It is a problem that should be 

 investigated, not on the basis of a certain number 

 of cells of each kind but rather on the basis of 



various cytologic effects produced in each cell 

 type. Cellular reactions of the kind shown for 

 the thrombocytes appear so frequently in birds 

 inoculated with lymphoid tumor material that 

 they deserve further study. 



Kasarinoff (1910) described hypertrophy of 

 thrombocytes with an increase in vacuolization 

 following the subcutaneous injection of sodium 

 cantharidate. Schogar (1939) described the 

 morphology of thrombocytes in pigeons and di- 

 vided them into four categories: Normal, youth- 

 ful forms, forms in old age, and forms under 

 stimulus. It seems probable that our reactive 

 thrombocytes include his last two categories. 

 The aging of thrombocytes has received practi- 

 cally no attention, except by Schogar, and yet it 

 is a subject that might be pursued with consider- 

 able profit. There seems little doubt that the 

 reactive thrombocytes are the ones with vacuoles. 

 Gray, Snoeyenbos and Reynolds (1954) have 

 photographed this type of cell in their study on 

 the hemorrhagic syndrome of chickens. Aged 

 cells may possibly be of the types shown in our 

 figures 81 and 84. 



In the amphibian, Nectitrus, Dawson (1933b) 

 found that thrombocytes had the power to phago- 

 cytose colloidal particles of carbon. These par- 

 ticles tended to aggregate at the poles, like the 

 specific acidophilic granules of thrombocytes. 

 Later (1936b) he showed that the particles of 

 carbon persisted in the cytoplasm of circulating 

 thrombocytes as long as a year, but he concluded 

 that the individual cell probably sui-vived only 

 aliout 5 months. The thrombocyte is a highly 

 labile cell and survival even this long seems 

 rather surprising, yet his conclusion is justified 

 by the data of his experiment. 



This property of phagocytosis may be peculiar 

 to particular species. Hartman (1925) in his 

 classification of diflferent types of thrombocytes 

 among vertebrates, noted phagocytosis in the 

 thrombocytes of the amphibian Bathrachoceps at- 

 tenuatus (Eisen) and in the reptile, I guana tuber- 

 culata. 



Figures 80, 82, and 83 illustrate a structural 

 series but it is not known whether progression in 

 this series is from right to left or from left to 

 right. As already mentioned, figure 80 closely 

 resemliles a lymphocyte except for the identify- 

 ing specific granules. Figure 90 is a lympho- 

 cyte from the same slide; it has a similar cyto- 

 plasmic texture and nuclear structure. In fig- 



45 



