98 TRANSITORY CAVITIES IN THE CORPUS STRIATUM. 



According to Grosser (3, p. 224) : "Regel-massig finden sich in Zottenstroma bei Eiern 

 des ersten Schwanger-schaftsmonate, grosse, protoplasma-reiche Zellen, auch die in letzter 

 Zeit wieder Hofbauer aufmerksam gemacht hat, deren Bedeutung aber noch unklar ist." 



These two authors are at a loss to explain the existence of the cells, while Minot (8, 

 p. 498 ff.) regards them as erythrocytes which have wandered into the mesenchyma, and, 

 remaining there, have swollen by imbibition and are undergoing degeneration by vacuoliza- 

 tion of their protoplasm. In figure 361 this author has illustrated "degenerating blood-cells" 

 in the chorion of embryo 350 — an embryo included in this study. Such an interpretation 

 finds little or no support from my observations. The vacuolization of the protoplasm sug- 

 gests degeneration, but such an hypothesis is overwhelmed by many other factors pointing 

 to a very active life — i. e., mitosis, phagocytosis of foreign material, evidences of amoeboid 

 movement, and lack of hemoglobin. Then, too, his figure 361 gives a false impression of 

 the relative size of a normal erythrocyte and these large phagocytic cells (cf. figs. 13, 15, 

 18, 22, and 31). The former may easily be accommodated in the body of the latter, and 

 only the largest red cell that one can find shows any approach to the size of the phagocyte. 

 Most observers have regarded these colorless cells as the ancestors of the blood elements, at 

 least whenever they are found in the body of the embryo itself. O. van der Stricht (11) 

 includes under the class of phagocytes "leucoblasts" which correspond exactly to these cells, 

 so widely distributed through the whole ovum. Saxer (10) derives them from the common 

 vascular and blood anlagen, which he differentiates from connective-tissue elements. From 

 these primary "Wanderzellen" of Saxer descend a series of cell-forms, including giant cells, 

 wandering cells of I, II, and III orders, erythrocytes, and colorless cells. The Wander- 

 zellen persist into adult life and continue their blood-forming powers in the bone marrow 

 and adenoid tissues. 



Maximow (6) holds that the embryonic ancestor of this cell is the mesenchyme out of 

 whose network it is gradually separated to become a free-moving cell. With the exception 

 of the extremities and gill-arches, he finds these "Wanderzellen" everywhere in the loose 

 mesenchyme, "allermeisten sich in Kopfmesenchym in der Nahe der Gehirnwand, vornehm- 

 lich an ihrer ventrolateralen Seite befinden." 



For a long time, morphologically similar cells have been recognized in the adult as 

 playing an important role in inflammation. It has recently been shown that these probably 

 have no relationship to the normal blood elements. Metchnikoff (7) has given the cells 

 of this class the name of "macrophage." This term has been adopted here because of its 

 application by recent observers' to a group of cells normally inhabiting the connective 

 tissues, serous cavities, and hematopoietic organs. The remarkable peculiarities of the 

 adult cells characterize them even in the very young embryo. This will be seen from the 

 following description, for although they are wholly unlike the young and incompletely differ- 

 entiated tissue in which they are found, they correspond with striking exactness to those of 

 the adult. A very clear physiological relationship between the widely distributed adult cells 

 has been demonstrated by Dr. Evans (2) by means of vital stains; his results have led me 

 to include these cells in the same class because of their morphological characteristics. 



While Hofbauer's use of stains is hardly analogous to their introduction as vital dyes, 

 it is interesting to note that by teasing living chorionic villi in solutions of neutral red, he 

 found (p. 124), "Wahrend alles (darunter auch das Syncytium) ungefarbt blieb oder einen 

 leichten Stich in Rosa annahm, treten die ' vakuolaren' Zellen der Zotte tief saturiert gefarbt 

 und beherschen die Bildflache." Plato (9) showed that cells engaged in phagocytosis are 

 particularly prone to stand out brilliantly in supravital stains because of the deep tingcing 

 of their phagocytized contents. Such evidence would account for Hofbauer's finding. 



