HamILton, Diveszon of Cells in Nervous System. 317 
cell multiplication for the later stages of development which is 
different from that of the earlier. In the earlier stages, we find 
ventricular germinal cells dividing and their offspring gradually 
transformed to neuroblasts and supporting cells. In the later 
stages this process is replaced by the repeated division of imma- 
ture neuroglia cells and immature nerve cells, which are un- 
doubtedly specialized cells, but are not yet fully developed. 
How long these cells retain their capacity for repeated 
division it is impossible to say, but apparently in the case of 
the white rat both kinds of cells continue to be capable of 
miotsis after the end of the 4th day of extra-uterine life. 
Summary of Part L1. 
1. There are at least two kinds of dividing cells in the 
central nervous system of the white rat; one small, with no 
visible cell-body, the other large with a well developed cell-body. 
2. The neuroglia cells are derived from the small dividing 
cells ; the nerve cells from the large ones. 
3. The dividing cells found in the gray matter and fiber- 
tracts of the brain and cord, are not indifferent cells, but are 
partly differentiated, and by their size, character of cell-body 
and nucleus and predominant distribution, it is possible to tell 
which are to be nerve cells and which supporting cells. 
4. Mitotic figures are occasionally found in multipolar 
nerve cells and in sporgioblasts. 
LITERATURE. 
1. ALTMANN. Ueber embryonales Wachstum, Lerpezg, 1881. 
2. His, WILH. Anatomie menschlichen Embryonen, Le7/zig, 1880. 
Die neuroblasten und deren Entstehung in embryonalen Mark. 
Abhancl. math. physikal Klasse konigl. Sachs. Ges. Wiss. XXVI. 
3¢ RaupBer. Ueber das Dickenwachsthum des Gehirns. Srlzungsber. d. 
naturf. Gesellsch. zu Leipaig, 1882. 
Hoffmann- Rauber, Lehrbuchd. Anat. d. Menschen, 11 Bd. 2 Abth. 
Erlangen. 
4. Merk, L. Die Mitosen im Centralnervensystem. Denkschr. d. math. 
naturw. Klasse d. katserl. Akad, Wiss. LIII, Wien. 
