178 VICTOR E. EMMEL 



had been advanced and discussed at several times in the history 

 of the subject, but through a lack of sufficient evidence the theory 

 has in more recent years received but little serious considera- 

 tion. Attention may be called first to the nature of the data 

 which Rindfleisch ('80), to whom the origin of the theory of nu- 

 clear extrusion is generally traced, himself advanced in support 

 of the extrusion view. Although it seems Rindfleisch has been 

 credited with saying that the nucleus is extruded from the cell free 

 from any cytoplasm such is not his original statement. On the 

 contrary he describes (p. 33) and figures the nucleus which has 

 left the cell as surrounded by an appreciable quantity of cyto- 

 plasm. It is a fact worthy of note that if one examine his draw- 

 ings in figure 6 for the embryo of the guinea pig illustrating stages 

 in nuclear extrusion, it is surprising how nearly they correspond 

 in appearance to processes of constriction described for the pig 

 embryo. To one who has observed the constriction process in the 

 living erythroblast the similarity in this figure is sufficiently 

 evident to suggest that what Rindfleisch described from fixed 

 preparations as extrusion might possibly have been explained 

 in terms of cytoplasmic constriction. 



Indeed, contemporaneously with Rindfleisch, just such an hy- 

 pothesis was advanced by Malassez. In 1878 in a study of the 

 spleen, and more fully in 1880 and 1881 in the bone marrow of the 

 rabbit, deer, calf, cat, and man Malassez carefully described and 

 figured for erythroblasts bud-like elongations of the cytoplasm, 

 which, although without having observed the actual process, 

 he assumed subsequently to separate from the parent cell and 

 become non-nucleated red corpuscles: /'Pour moi done, ces 

 elements ne se transforment pas en globules rouges par suite de la 

 destruction ou de la sortie de leur noyau; ils conservent leur indi- 

 vidualite, leur protoplasma produit un bourgeon qui, venant a se 

 detacher, forme un nouveau globule" (p. 15). Engel ('93, '98 

 and '99) from studies of mouse, pig ,and human embryos drew the 

 conclusion, reafl^rmed in 1906, that there occurs in erythroblasts 

 a mode of direct division separating the original cell into two parts, 

 the one nucleated, the other non-nucleated. Similarly Janosik 

 ('02), although more data and figures could be desired in his evi- 



