100 TRANSITORY CAVITIES IN THE CORPUS STRIATUM. 



of erythrocytes free in the tissue-spaces is not unfortunate, since they have stimulated these 

 macrophages to unusual activities whenever it occurred in their neighborhood. Embryo 

 406 furnishes many examples of red cells ingested by these large mononuclears in the cavi- 

 ties of the corpus striatum. Figure 26 is particularly interesting, as it illustrates a remark- 

 able phenomenon, namely, the division of a cell with a large mass of foreign material in its 

 cytoplasm. One of the asters is found on the edge of the cell, while the other' lies beneath 

 the ingested nucleated red blood-cell, and could not be drawn without confusing the picture. 

 Figure 27 shows the beginning digestion of the erythrocyte. Here the large macro- 

 phage from the cavum laterale corporis striati contains two smooth spheroidal bodies, 

 stained decidedly pink, yet not as deeply colored as the erythrocyte contained in the 

 dividing cell (fig. 26). Erythrosin has a marked affinity for cells containing hemoglobin, 

 and it here reveals these inclusions as two homogeneous globules. There is no evidence 

 of a nucleus in either of these two hemoglobin-containing fragments. Embryo 74 contains 

 cells which show the last stages of erythrocyte digestion (fig. 28). Here the macrophages 

 contain a few granules of brown pigment— not very unlike the large phagocytic cells known 

 as "Herzfehlerzellen," in the sputum of patients suffering from chronic passive congestion 

 of the lungs. It is very certain that long after the embryonic heart has stopped beating 

 and erythrocytes have been forced out of the capillaries, these huge amoeboid cells continue 

 to be actively engaged in the ingestion of foreign bodies. Even up to the time of fixation, 

 apparently, these cells are functioning, if mitotic division may be used as an index of a living 

 cell. It is easy to understand how some of these red cells may be reduced to brown pigment 

 granules when one considers the length of time which often elapses between the separation 

 of the placenta from the uterine wall and the fixation of the specimen. Careful, prolonged 

 search has been made to determine the presence of nervous tissue in the bodies of the 

 phagocytic cells inhabiting the corpora striata. In no instance was it possible to identify 

 with certainty any of the inclusions as neuroblasts. 



Most of the cells contain a single nucleus, for the most part eccentrically placed. It 

 is large, varying from 4 to 6m in the younger embryo and from 5 to 8m in the older, and has 

 a distinct nuclear membrane. The rich chromatin network with its many enlargements is 

 beautifully shown in the specimens stained with hemotoxylin. Many of the cells have 

 nucleoli attaining at times a diameter of 2 M . These are then the center of a radiation 

 of chromatin threads. The nucleus may be irregular in shape, as shown in figures 12, 13, 

 and 28, but in most instances it has a smooth contour. The irregular nuclei belong to cells 

 which have begun to show signs of degeneration. As they grow older they gradually lose 

 their power of staining and finally disappear. The eccentricity of the nucleus is a most 

 striking peculiarity. One commonly sees the nucleus in direct apposition to the cell- 

 membrane. Perhaps the only instance of a lack of similarity between the macrophages of 

 the embryo and those of the chorionic villi is to be found in the method of regeneration. 



Everywhere in the mesenchymal spaces, and especially in the cavities in the corpus 

 striatum, it is not difficult to find mitotic figures in these phagocytes (figs. 24, 25, 26); 

 in contrast to this one very rarely comes upon a dividing macrophage in the chorionic villi. 

 Figure 16 is an illustration of such an instance. It must be noted that all of the charac- 

 teristics described for the protoplasm are retained during mitosis— loose texture, vacuoliza- 

 tion, and engorgement with foreign particles. Cells with two nuclei have been observed 

 in the brain cavities, and the peculiar protoplasmic strands which sometimes bridge the gap 

 between them are illustrated in figure 29. The size of the nuclei, as well as the presence of 

 a nucleolus, in only one of them, makes it probable that we are dealing with direct division 



