THE DIVISION OF DIFFERENTIATED CELLSIN THE 
CENTRAL NERVOUS SYSTEM OF THE 
WHITE RAT. 
By Auice Hamitton, M.D. 
(From the Neurological Laboratory of the University of Chicago.) 
With Plates XIX, XX. 
Part I. NuMBER AND POSITION OF THE DivipING CELLs. 
The investigations which form the subject matter of this 
paper were undertaken in connection with a series of studies on 
the development of the central nervous system of the white 
rat, now being carried on in this laboratory. 
At the outstart the question to be solved related only to 
the number and distribution of the dividing cells in the central 
nervous system of the new born white rat, but in the course of 
the investigation other problems suggested themselves and led 
to a study of the character of the dividing cells as well. 
The white rat was chosen as material because of the abun- 
dant data relative to its development, which were already avail- 
able in the laboratory, and also because of the immature condi- 
tion of the nervous system at birth. The study was not, however, 
confined to the new born rat, although the investigations upon 
the animal at this stage were more extensive than those made 
upon earlier and later stages. Foetuses of about 17 mm. in 
length ' were examined, and also rats 1, 2, 3, and 4 days old. 
The material was hardened in Grar’s fluid,? and in FLEm- 
1 The aggregate weight of the 4 foetuses examined was 3.09 g., each foe- 
tus being about 17 mm. in length. 
: Oxalic acid 84, 4 vols. 
Alc. 95%» 3 vols, 
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