NUMBER OF OVA: ALBINO RAT 407 
(06), the thickness of the ovary of a woman nineteen years old 
is on the average (left and right) 13:4 mm. If the sections were 
made 0.05 mm. in thickness, the total number of sections would 
be at least 270. From 270 sections, therefore, Heyse selected 
only forty-two sections, that is about one-sixth of the total ovary. 
Moreover, the distribution of follicles in the mature ovary is 
not so uniform as in the ovary of the new-born, but varies enor- 
mously between two sections when taken some distance apart. 
Therefore, Heyse should have counted at least half of the total 
ovary in order to obtain a fairly approximate number. 
Joessel and Waldeyer (’99, p. 793) state that both ovaries of a 
new-born child contain 100,000 or more ova, but it is explicitly 
added that this is merely an estimate and probably too low rather 
than too high. 
Sappey (’79) made a determination of the number of ova by 
counting those found in 1 sq. mm. of the section and then com- 
puting the number which should be present in the entire ovary. 
His numbers are very large. In one girl of three years he esti- 
mated 422,000 ovain oneovary. In another of four years675,000, 
and in a third child 300,000. In a young woman of eighteen 
years he reports 300,000 in one ovary. Why these numbers are 
so high I cannot at the moment say. 
The latest study on the number of ova in man is that by v. 
Hansemann (713). I have taken the liberty of tabulating his 
results, which were obtained by counting the number of ova in 
every fifth section from a complete series of sections for each 
ovary. The number of ova thus counted was multiplied by five, 
and the results are those given. It is difficult to determine from 
the text whether the final number represents the ova in one or in 
both ovaries, but I assume that the numbers are for one ovary 
only.! 
1 Several of the authors here quoted on the number of ova in man do not make 
it plain whether their numbers apply to one ovary or to both, so that I have had 
to decide the question by inference in most cases. In the article by v. Hanse- 
mann (’13) reference is made to the statement by Minot (’92) that there are 70,000 
ovainman. This is evidently based on Henle’s determination. Waldeyer (’06) 
(in Hertwig’s Handbuch) states that there are probably 50,000 ova in each ovary 
of the human fetus. 
