70 Proceedings of the Royal Irish Academy. 



period, too, the theca externa may thin out and even disappear at certain 

 places around tlie corpus luteuin. In such cases all sharp delimitation between 

 the corpus luteum and the ovarian stroma, vfith its rich interstitial glands, is 

 effaced, (c) Then follow the stages of involution or atrophy. These changes 

 set in some time before the birth of the embryo, and are characterized by a 

 hypertrophy of the connective tissues of the corpus luteum, spreading from 

 the centre of the organ towards its periphery. Step by step the corpus 

 luteum shrinks till all that is left of it is an almost solid connective tissue 

 nodule, which among human anatomists is called a corpus albicans. 



From the work of various observers it does seem probable tliat there are 

 two periods to be distinguished in the secretory history of the corpus luteum. 

 Most of the authors on this subject seem to agree that the deposition of fat 

 in the luteal cells in its later stages is not a sign of degeneration, but 

 represents a normal function of an endocrine nature. Van der iStricht is very 

 emphatic in disagreeing with Mile. Niskoubina Nadiejda and Pottet, who claim 

 that the appearance of fat in the human corpus marks the beginning of fatty 

 degeneration. 



Van der Stricht says: " Dans le corps jaune de la Chauve-souris, on ne 

 constate point de processus de destruction cellulaire semblable [a glanues 

 sebacees], les elements giandulaires se montrent merocrines." 



This observer, speaking of the physiology of the corpus luteum, makes the 

 following statement : - " Apr^s avoir demontre que ie corps jaune de la Chauve- 

 souris fournit au sang de la mfere uue substance sereuse, pregraisseuse, surtout 

 abondante durant la p^riode de la migration de I'ovule, et un produit lipoide 

 qui remplace graduellement la premiere, a partir de I'arret de I'ovule et de sa 

 fixation dans la corne uterine, il nous semble rationnel de conclure, en 

 admettaut I'exactitude des experiences phy.siologiques des auteurs precddentes, 

 que la secretion sereuse exerce son influence sur les transformations uterines 

 de la premiere phase de la gestation, pendant le deplacement de I'oeuf, et que 

 la secretion lipoide intervient principalement pour provoquer I'arret et la 

 fixation du blastocyste et la formation du placenta." 



While I recognize that the physiological function of the corpus luteum may 

 not solely be that of preparing the uterine walls for the implacement of the 

 ovum, it is diflicult to understand what cytological evidence this distinguished 

 continental observer has brought forward to support his views as to a primary 

 serous and then a secondary lipoid type of secretion. As will be mentioned 

 below, the work of Allen and Duisy throws quite a bright light on this 

 subject, and I believe that Van der Stricht may have to modify his views. 



J. P. Hill and the present writer have given an account, now in press, of 

 the formation of the corpus luteum of Ornithorhyuchus, the duck-billed 



