AUTHOR’S ABSTRACT OF THIS PAPER ISSUED 
BY THE BIBLIOGRAPHIC SERVICE, JULY 12 
ON THE POSTNATAL DEVELOPMENT OF THE OVARY 
(ALBINO RAT), WITH ESPECIAL REFERENCE 
TO THE NUMBER OF OVA 
HAYATO ARAI 
The Wistar Institute of Anatomy 
FOUR CHARTS 
INTRODUCTION 
Numerous data on the postnatal development of the ovaries 
of lower mammals are to be found, but, so far as I am aware, 
there are no investigations on the number of ova in these ani- 
mals. For the human ovaries, however, there are five observa- 
tions on the number of ova, though the techniques used by several 
authors are open to some criticism. 
Strange to say, despite the great emphasis recently placed on 
the study of reproductive phenomena, especially in relation to 
the questions of inheritance, sex difference, or of physiology of 
the internal secretions, no one has attempted to obtain funda- 
mental data on the number of ova in the ovaries, although such 
data may throw some definite light on the various problems in 
the physiology of reproduction. 
I have taken this study of the total number of ova in the rat 
during the entire span of life at the suggestion of Prof. H. H. 
Donaldson, to whom I am happy to acknowledge my indebted- 
ness not only for his deep interest shown during the progress of 
the work, but also for numerous .suggestions while preparing 
this paper. 
I shall first present the data on the number of ova in human 
ovaries as reported by the five investigators. 
Henle (’73) estimated the number of the follicles in an ovary 
of an eighteen-year-old woman, and stated that it contained 
about 36,000 follicles, or not less than 72,000 in both ovaries. 
The method by which he estimated this number is as follows: 
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