CHICKEN BONE MARROW IN PLASMA MEDIUM 97 



washed out by continued changing of the plasma, on the sec- 

 ond incubation are allowed to develop we find after a fortnight 

 two different types: figures 20 and 21, and figures 22 to 24. 

 The cell represented in figure 21 differs from the basophil cells 

 which had been implanted into the tissue culture (fig. 8, and 

 figs. 36 and 37) onlj^ by its size and by the more chromatic con- 

 tents of its nucleus. These forms are numerous; they later 

 contain fat or vacuolize, forming chains, the cells of which are 

 always to be distinguished by their nuclear structure from the 

 eosinophil leucocyte. The nucleus has a close resemblance to 

 that in fat cells; it is vesicular with round bulky, chromatic 

 contents. 



The next group (figs. 22 to 24) have a true connective tissue 

 cell-like nuclear structure. The nuclei are elongated and fine 

 threads of chromatin form a true connective tissue nucleus net- 

 work. The cytoplasm is basophil in most cases, but in cer- 

 tain parts of the culture and in very old cultures it becomes 

 acidophil. The basophily or acidophily of cells is no constant 

 character in tissue cultures. Rous ('13, page 183) points out 

 the changes in acidity of growing cells. The cells themselves 

 become acid in the culture medium, after having been basophil. 

 Later they may regain their basophil character. The cells in 

 question are true phagocytes (fig. 23). They contain fat, blood 

 corpuscles, dead nuclei, and other disintegrating particles. They 

 are sometimes polynuclear; as the cell body does not divide they 

 form also the so-called 'Riesenzellen' of Foot. They are more 

 agile after the first days' of incubation. In older cultures they 

 assume round, spherical and oblong shapes, and their enormous 

 protoplasmatic body divides up. They then form the cell cul- 

 ture type (fig. 6) the nuclei of which are always vesicular and 

 not very chromatic. 



Therefore, in the group of Foot's 'Riesenzellen' do belong be- 

 sides the products of the involution of the fat cells and the 

 implanted elongated connective tissue celltype with its finely 

 vacuolized plasma, these forms (figs. 22 to 24) in which the 

 nearly fat-less bone marrow of a young chicken was used. This 

 gave conclusive proof that the small mononuclear basophil cell 



THK AMKHK AN JOIKNAL f)r ANATOMY, VOL. 22, NO- 1 



