408 HAYATO ARAI 
Number of ova in one (?) ovary of man at different ages (v. Hansemann) 
Age - Number of Ova 
G:DIMOntHS Thre Sheena ioe gc eae ee eee teas oo Siaesneet ae ene 30,339 
PEveaTr ZrMOMblUss ch. wets s ciaie che sre oct nereTs as ots cokes et ae ree 48,808 
DEV CARS Ae ele Rote eRe ea ead ha reed tote T AMM Nak creates ate Sic ates ene eae 46,174 
Si Vearse asf tect. Vasey eins ieee Sane nd cele eet seloe nae 25,665 
NO OOPS Sos ede cctoe ne Rae = lle sions fas Pb rosters ebe © opereutecielga® eve Sie etegs ke Cheese 20,862 
VAP Vi CATS. « siesne-e racy eel ieeiivage e504 iy Tesyeas ageye eee nek cdot teas acklege a eS eee 16,390 
LCOS VOATS omen eee on a tints Soe ee Se et cece eee 5,000-7,000 
While there is still some doubt whether the numbers given by 
v. Hansemann are for one or for both ovaries, yet they show 
clearly what the previous data suggest; namely, that there are 
many more ova present during the earliest years of life than 
at puberty, and that even after puberty the numbers show a 
significant decrease. 
To obtain some accurate information regarding the relation 
between the number of ova and the age of the animal, I have 
utilized the ovaries of albino rats. 
MATERIAL AND TECHNIQUE 
The material used in this study was all supplied from the rat 
colony at The Wistar Institute. The number of rats examined 
for the standard table was thirty-nine—from one day after 
birth to 947 days of age—and the material was collected during 
seven months—from April to November, 1918. 
In each instance the body weight, body length, the weights of 
the ovaries, and the appearance of corpora lutea were recorded. 
The removal of the ovary, especially when the rats are very small, 
requires some practice. Each ovary was quickly weighed and 
then fixed in Bouin’s solution for from six to eight hours. The 
material was washed in running water for twenty to thirty min- 
utes, sometimes for one hour, run through the alcohols, cleared 
in xylol, and finally imbedded in paraffin. Each entire ovary 
was sectioned in series at 10 », and the sections were stained with 
hematoxylin and eosin. 
In order to obtain approximately the true number of ova in 
the ovaries, I have counted under the microscope the nucleus of | 
every ovum in the series of sections obtained from each entire 
