CELLULAR ELEMENTS OF THE MAMMALIAN EMBRYO 79 



No evidence was obtained as to the exact nature of this change 

 in the staining qiiahties of the cytoplasm of the phagocyte — 

 whether it is the result of an internal absorption of digestion 

 products or whether it is due to a modification or reduction of 

 cytoplasmic elements of the phagocyte itself as they participate 

 in the digestive processes. In either case it is remarkable how 

 constant and sharp is the demarkation between the cytoplasm 

 of the phagocyte and that of the ingested cell, and that one is 

 able to detect httle if any difference in the cytoplasm of the 

 phagocyte in the immediate vicinity of the inclusion as com- 

 pared with that in the more remote parts of the same cell body. 

 It is to be observed that these color changes in the phagocyte 

 are apparently not confined exclusively to its cytoplasm for the 

 nucleus also may become much lighter in the highly active 

 macrophags, a change involving apparently the nucleoplasm 

 rather than the chromatin (cf. figs. 1, 2, 9 and 14 ic7n, with 5, 

 6, 10, and 14 pern). These cytoplasmic and nuclear differences 

 appear especially well demonstrated in figure 8. These two 

 cells frcm the pericardial cavity of a 9 mm. pig embryo were ly- 

 ing side by side in the manner drawn. Consequently there can 

 be no question of variation in fixing or staining technique as factors 

 in their staining differences. In (a) both nucleoplasm and cyto- 

 plasm are quite basophilic, while in (6) which is at a comparatively 

 much higher stage of phagocytic activity, nucleoplasm and cyto- 

 plasm are both much paler in color. The same observation also 

 applies to figures 9 and 10 which were taken from two consecu- 

 tive sections of a second 9 mm. pig embryo. In examining the 

 literature bearing upon this subject it is of interest to note that 

 similar changes in the basophilic character of the cytoplasm is 

 described by Downey ('10) in the phagocytes of the lympho- 

 renal tissue of the ganoid fish, Polyodon spatula, as indicated in 

 the statement that ''as seen in Polyodon these cells are strongly 

 basophilic right after phagocytosis (fig. 2) . As the phagocytosed 

 erA^throcyte breaks down the cell gradually becomes pale and 

 often metachromatic" p. 85.^ 



' Kyes ('15, p. 546) in a recent paper also describes in the liver of birds varia- 

 tions in nuclear structure and cytoplasmic staining reaction of endothelial cells 

 as correlated with the intra-cellular digestion of ingested erythrocytes. 



