AUTHOR'S ABSTRACT OF THIS PAPER ISSUED 
BY THE BIBLIOGRAPHIC SERVICE, FEBRUARY 2 
COMPARATIVE STUDIES ON THE GROWTH OF THE 
CEREBRAL CORTEX 
V. PART I. ON THE AREA OF THE CORTEX AND ON THE NUMBER 
OF CELLS IN A UNIT VOLUME, MEASURED ON THE FRONTAL 
AND SAGITTAL SECTIONS OF THE ALBINO RAT BRAIN, TOGETHER 
WITH THE CHANGES IN THESE CHARACTERS ACCORDING TO THE 
GROWTH OF THE BRAIN 
V. PART II. ON THE AREA OF THE CORTEX AND ON THE NUMBER 
OF CELLS IN A UNIT VOLUME, MEASURED ON THE FRONTAL 
AND SAGITTAL SECTIONS OF THE BRAIN OF THE NORWAY RAT 
(MUS NORVEGICUS), COMPARED WITH THE CORRESPONDING DATA 
FOR THE ALBINO RAT 
NAOKI SUGITA 
From the Wistar Institute of Anatomy and Biology 
THREE FIGURES AND FOUR CHARTS 
PART I 
I. INTRODUCTION 
The present study is an extension of an earlier one on the 
thickness of the cerebral cortex in the albino rat (Sugita, ’17 a) 
and aims to present the extent of the actual area occupied by 
the cortical cells, as seen in sections which were taken from 
the fixed levels of the albino brain, and also to follow the 
changes in this area during the postnatal growth of the brain. 
In the course of this investigation, the number of nerve cells 
contained in a unit volume of a fixed locality in the frontal) 
section was counted and the changes in this number with ad- 
vancing age were ascertained. Furthermore the relation be- 
tween the cell number and the cortical area was critically 
examined. 
For this study, the sections, which had been previously used 
for the investigation of the thickness of the cortex of the albino 
rat brain, were again utilized. The material, amounting to 78 
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THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 29, NO. 2 
APRIL, 1918 
