THE CORPUS LUTEUM 363 



between corpora albicantia of ovulation and pregnancy. The total size range of corpora lutea of 

 ovulation and pregnancy is 16-0 cm. and the overlap is 7-3 cm., so size alone cannot be diagnostic. 

 It is suggested below that size correlated with a quantitative measurement of histological regression 

 could perhaps be used to distinguish these two types of corpora in individual females. 



Van Lennep also suggests that two types of corpora albicantia can be distinguished, those with 

 straight connective tissue trabeculae and those with branched trabeculae. He suggested that ' Most, 

 if not all, corpora albicantia of the first type are probably derived from corpora lutea of ovulation as 

 only young corpora lutea of pregnancy have been found to possess the same structure and may there- 

 fore be supposed to become corpora albicantia of the second (branched) type' (p. 597). It is shown 

 later that these types of corpora albicantia correspond to vesicular and non-vesicular corpora lutea 

 respectively. In fact van Lennep's distinction is the reverse of that suggested by Robins. Finally, 

 mention must be made of the comprehensive paper of Dubreuil and Riviere (1947), who conclude 

 that there is still no certain means of distinguishing the human corpora lutea of pregnancy and ovula- 

 tion. Much attention has been given to this subject because of the legal implications. The work of 

 Peters bearing on this problem will be discussed in the next section (p. 384). 



CORPORA ALBICANTIA, CORPORA ABERRANTIA AND 



CORPORA ATRETICA 



The corpus albicans 

 The corpus luteum of ovulation after 2-3 weeks and the corpus luteum of pregnancy after about 

 1 1 months undergo degenerative changes and rapidly shrink in size. The luteal cells disappear, the 

 colour of the former lobes of luteal tissue changes to a tawny brown and the white connective tissue 

 septa become increasingly more conspicuous (PI. V, fig. 1). 



There is some confusion about the nomenclature of the body so formed. The regressed corpus 

 luteum of the whale is not properly a corpus albicans, a term which is correctly applied to the 

 unpigmented old corpora of certain other animals. Usually some pigment remains even in the very 

 old corpus of the fin whale and the more recent regressing bodies are well pigmented like the corpus 

 rubrum of the cow, although they are a yellow-brown in colour. The term corpus fibrosum might be 

 applied to the old corpus which has lost most of its pigment. 



Mackintosh and Wheeler (1929) refer to the active corpora lutea and the regressed corpora lutea 

 as corpora lutea a and b respectively. The latter is technically a more correct terminology than corpus 

 albicans, but it leads to confusion. The term corpus albicans is now generally used to describe old 

 corpora lutea whether pigmented or not, and to avoid introducing yet another terminology it is 

 proposed to refer to all old corpora lutea as corpora albicantia. 



The corpus albicans material is much more extensive than that available for study of the corpus 

 luteum, because one pair of ovaries may contain over fifty corpora albicantia, but usually only one corpus 

 luteum. In 1953/54 a detailed study of 1381 fresh unfixed corpora albicantia was undertaken by the 

 author in F/F ' Balaena ', and various morphological types were distinguished. These ovaries were 

 sliced by hand. Unfortunately no large collection of fin-whale ovaries was undertaken in 1954/55, 

 and it was not until after the 1955/56 season that a collection of ovaries became available for routine 

 examination. Using a slicing machine cutting at 5 mm., all the corpora above about 7 mm. were 

 examined and some of those smaller than this. In all 4065 corpora albicantia were systematically 

 examined, classified and measured. It is necessary to make clear one important point about the 

 measurements. In calculating the mean diameter of the corpus luteum, measurements were made 

 on three axes. Since most corpora albicantia are embedded in the ovary and do not project like the 



