INTERNAL SECRETION OF CORPUS LUTEUM 197 



for the opossum by Hartman (272), for the spermophile by 

 Drips (170), and for the mouse and the rabbit by Harris (270) 

 and by Corner (127). 



Since the opossum is aplacental, Hartman's (272) results are 

 of particular interest in showing that the effect of the corpus 

 luteum is not solely concerned with facilitating implantation. 

 In addition to the above, cases have been recorded by Hammond 

 (264) and Hartman (277) in which abnormal degeneration of 

 the corpora lutea during pregnancy has led to foetal death. 



By means of the unilateral sterilization technique (described 

 on p. 176), it has been possible to get very definite results on 

 mice (499). Unilaterally sterilized mice become pregnant quite 

 readily from the untreated ovary, which undergoes considerable 

 compensatory hypertrophy. In such pregnant mice the removal 

 of the untreated ovary containing the corpora lutea invariably 

 results in the termination of pregnancy. The abortion following 

 the operation takes place 24-48 hours later, so that when the 

 operation is performed at the seventeenth day of pregnancy, 

 i.e. two days before parturition would normally take place, the 

 operative abortion and normal birth coincide. Removal of the 

 sterilized ovary containing no corpora lutea has no effect on the 

 gestation. From these experiments it may be concluded that in 

 the mouse the corpora lutea are necessary throughout pregnancy 

 until undergoing regression at about the seventeenth day, 

 forty-eight hours before parturition. There is thus considerable 

 discrepancy between the results of different workers in this 

 field, which may to some extent be due to the variation in the 

 methods used to. remove the corpora lutea and also to the 

 variety of animals employed. As regards the latter point, it is 

 improbable that closely related species, such as the rat and 

 mouse, would show any great difference in the necessity for the 

 presence of the corpus luteum, and moreover contradictory 

 results have been obtained by different workers on the same 

 species of animal. The w^eight of the evidence, however, favours 

 the view that the corpora lutea are essential during the whole 

 of pregnancy. 



