CHICKEN BONE MARROW IN PLASMA MEDIUM 83 



pyknotic and form round, chromatic bodies " (figs. 11 to 19). 

 The acidophil granules become more and .more indistinct, the 

 cytoplasm is again acidophil, and partly vacuolized. In this 

 stage, long chains of these forms closely lying together cover 

 the outer zones of the preparation, gi\ing it a reddish halo. 

 Later these cells without granules flatten out entirely, lose their 

 nuclei or their chromatic particles, and undergo total destruction. 



To summarize: most mononuclear and polymorphonuclear 

 eosinoiphil leucocytes with either round, kidney-shaped, or lobu- 

 lated nuclei, during the first hour of their emigration (fig. 8, and 

 fig. 43) into the surrounding plasma, divide rapidly. They 

 form smaller cells with fewer granules and a more basophil 

 cytoplasm. Later by dividing and moving to the outskirts of 

 the plasma clot, they finally form rays and layers of partly 

 acidophil, vacuolized 'cells' without nuclei and granules. An- 

 other group of these eosinophil leucocytes, before diminishing 

 in size in the zone near the implanted bone-marrow particle, 

 had extruded its granules at a very early period. They fade 

 out and leave their more basophil cell bodies in the plasma clot. 

 The mononuclear or polymorphonuclear eosinophil leucocytes 

 undergo a regressive development in tissue cultures. 



These conclusions agree with the writer's own observations of 

 the cells in living preparations. On the first and second day of 

 incubation the eosinophil leucocytes are numerous and of normal 

 size (fig. 2, left side, above). On the fourth and the fifth day 

 the few forms, which have not undergone the flattening-out 

 process and which have not changed their character, are small, 

 with fine granules and an ellipsoid nucleus (fig. 5, left side, 

 below). Foot ('13, pp. 49-51), in his account of the changes 

 of the eosinophil leucocyte in the culture medium, reports that 

 these cells finally take on the same form as that assumed later 

 by the large mononuclear lymphocytes, and cannot be distin- 

 guished from them. With this conclusion the present MTiter 

 cannot agree. In figure 8, the emigration of small leucocytes 

 is shown. The lean, almost fat-less bone-marrow orginated 

 from a young, not full-grown chicken. After an hour in an 

 identical preparation the tissue was extracted and only the 

 emigi-ated cells were allowed to develop. All cell types which 



