CORPORA ALBICANTIA, CORPORA ABERRANTIA AND CORPORA ATRETICA 375 



which about two-thirds are contributed by corpora lutea of ovulation and one-third by corpora lutea 

 of pregnancy. The regression is to a constant proportion of the former size, and corpora lutea of 

 ovulation and pregnancy do not appear to differ in this respect. A negligible proportion are missed in 

 the routine examination. 



It has been stated that the smallest corpus albicans which is expected to be observed in the routine 

 examination is about 7 mm. in diameter. Below this size it is probable that some will be missed 

 because the thickness of the slices is 5 mm. On the basis of the regression factor established above 

 a corpus albicans of 7 mm. corresponds to a corpus luteum of 3-2 cm. in diameter and it is therefore 

 likely that the majority of, but not all, corpora albicantia representing former corpora lutea under 

 3 cm. in diameter, are missed in the routine examination. 



2 3 



DIAMETER IN CMS. 



Text-fig. 20. A, size frequency distribution of all 'old' corpora albicantia; B, size frequency distribution of 'old' corpora 

 albicantia of pregnancy (calculated from Text-fig. 19); C, resulting size frequency distribution of 'old' corpora albicantia of 

 ovulation; D, calculated mean diameter +2S.E., and size range of 'old' corpora albicantia of ovulation (see text for 

 explanation). 



There was no corpus luteum of pregnancy smaller than 3 cm., but four out of 59 corpora lutea of 

 ovulation were under this size, that is, 6-8%. In terms of total 'old' corpora albicantia this will 

 represent 4-5% (because there are about two corpora lutea of ovulation to one corpus luteum of 

 pregnancy). The accessory corpora lutea, some of which do not represent ovulations, range from 

 0-5 to 8-5 cm. in diameter with a mean of 3-88 cm. so a larger proportion of them will be unrepresented 

 by observable corpora albicantia. In fact 11 out of 26 were under 3 cm. in diameter, that is 42-3%, 

 and since accessory corpora lutea comprise about 37% of all corpora lutea this amounts to about 

 i-6% of all' old' corpora albicantia. The accessory corpora lutea which are expected to be observed 

 when fully regressed, that is to say those which are initially 3 cm. in diameter or larger, amount to 

 2-1% of all corpora lutea. 



