96 HOWELL. [Vol. IV. 



corpuscles with only one or two small granules of nuclear 

 matter, which he takes to represent the last step in the disap- 

 pearance. There is very little satisfactory proof, then, for the 

 theory, since no one, of course, has been able to follow the 

 process through all its changes, and the appearances described 

 above might easily be explained in other ways. Nevertheless, 

 the theory has been generally adopted by those who believe in 

 the nucleated red corpuscle and its functions. Malassez, of 

 course, upon his theory of budding, is not obliged to explain 

 the loss of the nucleus, nor are those who believe in an endog- 

 enous formation of the red corpuscles ; but, outside of these 

 theories, which cannot be said to have a strong support at 

 present, the general belief among histologists is that the nucle- 

 ated red corpuscle loses its nucleus by absorption in the way 

 described by Kolliker and Neumann. There seems to be, in- 

 deed, only one other alternative : if the nucleated red corpuscle 

 changes to the non-nucleated form, the nucleus either disap- 

 pears by absorption within the cell or by extrusion from the 

 cell. This latter view has been seriously supported only by 

 Rindfleisch (26). As I have stated in the historical review, 

 Rindfieisch believes that the nucleus escapes from the nu- 

 cleated red corpuscle surrounded by a small layer of colorless 

 protoplasm, and leaves behind a bell-shaped corpuscle which 

 eventually becomes a biconcave disc. He figures corpuscles 

 in which the nucleus was seen in the act of escaping from the 

 cell. Others have seen similar examples of extruding nuclei, 

 but have concluded that it was an accidental and not a, normal 

 phenomenon. The chief result of my own work has been to 

 obtain what seems to me indisputable evidence that the extru- 

 sion of the nucleus is the normal method by which the nucle- 

 ated red corpuscle loses its nucleus and passes into the non- 

 nucleated form. Unlike Rindfleisch, I have never been able 

 to discover with the highest objectives (Zeiss Hom. im, -J^ and 

 apochromatic im.) that the escaping nucleus has an envelope 

 of protoplasm round it. On the contrary, it goes out of the 

 corpuscle entirely naked, and can be found as a free nucleus 

 in sections and teased specimens of the marrow, and also in the 

 embryonic liver, as has been previously described by Neumann 

 (see Fig. 2). In many cases in the marrow, and especially in 

 the foetal liver, I have seen the homogeneous nucleus partially 



