AUTHOR’S ABSTRACT OF THIS PAPER ISSUED BY 
THE BIBLIOGRAPHIC SERVICE DECEMBER, 15, 
COMPARATIVE STUDIES ON THE GROWTH OF THE 
CEREBRAL CORTEX 
IV. ON THE THICKNESS OF THE CEREBRAL CORTEX OF THE NOR- 
WAY RAT (MUS NORVEGICUS) AND A COMPARISON OF THE SAME 
WITH THE CORTICAL THICKNESS IN THE ALBINO RAT 
NAOKI SUGITA 
From the Wistar Institute of Anatomy and Biology 
TEN CHARTS 
I. INTRODUCTION 
In my second study in this series (Sugita, 717a), I described 
in detail the postnatal growth of the cortex in thickness in the 
brain of the albino rat. With the same purpose and by the 
same technique, I have examined also the growth of the cere- 
bral cortex of the Norway rat, the wild form from which the 
albino rat has been derived. Donaldson and Hatai (11) have 
been interested in a comparison of the wild Norway with the 
albino rats in respect of their body measurements and the size 
of the central nervous system. They have concluded that on 
account of domestication the albino rat grows less well than 
the wild Norway rat, from which it has been derived, and es- 
pecially that the relative weight of the brain of the adult albino 
rat is about 16 per cent less than that of the Norway rat of like 
body weight. It has been assumed as probable that the greater 
weight of the brain in the Norway rat is due to an enlargement 
of the constituent neurons rather than to an increase in their 
number. The percentage of water appears to be nearly the 
same in the central nervous system of both forms during the 
period of active growth, but after this period it remains slightly 
higher in the Norway rat. From these differences between 
the two forms as regards the weight and the water content of 
their brains, it is also inferred that there will be some structural 
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