406 ‘ _HALBERT L. DUNN 
Our knowledge of the growth of the central nervous system in 
the prenatal period is much less complete. While the numerous 
studies on the morphogenesis of the brain and spinal cord in the 
first trimester of fetal life enable us to draw some general con- 
clusions concerning the early prenatal growth of these structures, 
there are practically no quantitative data available for this period. 
Data on the later prenatal growth of the brain are more ex- 
tensive, and a survey of the literature gives about 500 published 
records of the weight of the brain between the third fetal month 
and birth. The more important of these collections are those of 
Rudinger (’77), Brandt (’86), Arnovljevicé (’84), Michaelis (’06), 
Jackson (’09), and Valtorta (’09). A small amount of this ma- ~ 
terial has been presented in graphic form by Zangemeister (711). 
The only collection of records of the weights or volumes of the 
various parts of the brain in fetal life seems to be a short series 
of figures on the cerebrum, cerebellum, and brain stem published 
by Valtorta (’09). 
The spinal cord has received far less attention than the brain, 
doubtless because of its smaller size and the technical difficulties 
of its removal. Our knowledge of the growth of the cord in post- 
natal life is very incomplete, being limited to the data of Pfeister 
(703) and Danielbekoff (’85). Information regarding the changes 
in fetal life is apparently confined to a study by Giese (’98), 
published as a St. Petersburg dissertation, which is available only 
in abstract at the present time. 
The following study was undertaken with the hope that a part 
of this large gap in our knowledge of human growth might be 
spanned by the systematic examination and measurement of the 
brain and spinal cord in a large series of human fetuses ranging 
from the second fetal month to birth, and by the treatment of 
these data by some of the more modern methods of statistical and 
graphic analysis. The work was done under the direction of 
Dr. R. E. Scammon, to whom the writer is very much indebted 
for constant advice and aid throughout the entire study. 
