566 MATURATION AND DISCHARGE OF OVA. [CHAP. XXXIX. 



colour, resembling effused blood; but soon the colour becomes 

 paler, while its consistence is firmer and more dense. At length 

 the follicle is seen to be occupied with a firm mass, which appears 

 to be formed from a secretion poured out from its walls, which, 

 from its yellow colour in man and many animals, has been called 

 corpus luteum. Hence, for every follicle in the ovary from which 

 an ovum is discharged, a corpus luteum will be found. In cases of 

 twins, two corpora lutea are always present ; sometimes one in each 

 ovary, sometimes two in one. The characters which the corpus 

 luteum exhibits, and the extent to which the changes giving rise 

 to its formation undergo, will be determined by the circumstance 

 of the ovum being impregnated or not. 



Bischoff proved decisively that the ova in mammalia were 

 detached from the ovary at the time of heat, without coition taking 

 place; and that corpora lutea were formed in the ovaries, just as 

 if coition had occurred, and impregnation had taken place. 



Raciborski, from numerous experiments upon animals, has shown 

 that whether the rupture of the follicles is or is not accompanied 

 by coitus or by fecundation, the appearance of the lesion which 

 results isj in both cases, absolutely identical. 



Nevertheless the corpus luteum of pregnancy, except in its 

 earliest stages, has been admitted by all observers, to possess cha- 

 racters by which it may be distinguished from the corpus luteum 

 formed in a follicle from which an ovum has been discharged 

 without subsequent impregnation having occurred. Hence, true 

 and false corpora lutea have been described ; the true occurring 

 only when conception has taken place, while the false are met with 

 in the virgin ovary, This distinction must undoubtedly be recog- 

 nised ; but there is every reason to believe that the development 

 of a true corpus luteum takes place in obedience to similar nutri- 

 tive changes which determine the formation of this body, proceed- 

 ing to a much greater extent than in the case of the false or virgin 

 corpus luteum, in consequence of their being promoted by the 

 increased determination of nutritive pabulum and the greater 

 vascularity of the ovaries when impregnation has occurred. 



In the cow (according to Dr. Dalton), the corpus luteum reaches 

 its maximum of development in about two weeks after the rupture of 

 the vesicle, and in three weeks more all that remains is a small 

 yellowish spot. If, on the other hand, the rupture of the follicle 

 be followed by impregnation, the corpus luteum does not attain 

 its greatest size till about the middle of the seventh month, and at 

 the termination of the eighth month it is still of large size, arid 



