298 JouRNAL oF CoMPARATIVE NEUROLOGY. 
MING’S solution, the former giving the best results. It was im- 
bedded in paraffin, and stained with iron-lack-haematoxylin, 
either alone or with erythrosin as a counter-stain, with saffranin 
and with toluidin blue and erythrosin. One series from the 
new-born rat was carried through by ViGcNAL’s method; i. e. 
alcohol-osmic acid hardening, picrocarminate of ammonia stain, 
—this method being said by ViGNAL to demonstrate the char- 
acter of the cytoplasm and processes unusually well. Unfor- 
tunately it does not stain the mitotic figures, so that it was not 
of much value for this study, except that it showed with great 
clearness the different forms of glia cells. Grar’s fluid and 
iron-lack-haematoxylin gave the most satisfactory results. 
The cord and cerebral hemispheres of the new-born rat 
were first studied, and therefore the results obtained from 
them will be given first. 
The cord of the new-born rat contained a large number of 
mitoses, which were found chiefly in the outer layers; the num- 
ber on the ventricular surfaces was suprisingly small. In the 
brain the ventricular mitoses were more numerous than in the 
cord, but here also the extra-ventricular predominated. The 
brain and cord of the 24-hour rat contained fewer mitoses than 
the new-born rat, while in the three days and four days old 
specimens the number seemed equal to that of the new-born. 
Comparing the foetus with these older specimens, a striking 
difference was seen, for here the mitoses seemed to be predomi- 
nantly on the ventricular surfaces. Figs. 1, 2, 3, 4. 
In order to decide the question beyond doubt the mitotic 
figures were counted in 15 sections, 634m in thickness, taken 
from the cerebral hemispheres and from the cervical, thoracic 
and lumbar regions of the cord of the new-born rat. Also from: 
the cerebral hemispheres and lumbar cords of the foetus and 
of the 24-hours and four day specimens. The sections of the 
hemispheres were coronal and taken at the level of the chiasma. 
The following tables give the results of these counts. 
