24 INTERNAL SECRETIONS OF THE OVARY 



ovarian changes are in progress cyclic events are proceeding 

 in the accessory organs of reproduction — uterus, vagina, and 

 mammary glands. These events are collectively known as the 

 ' oestrous cycle,' from oestrus, the central point of the cycle, 

 when ovulation and copulation take place. 



After the anoestrous or pre-pubertal period of comparative 

 quiescence the cycle starts with the preliminary phase of 

 prooestrus, during which the follicles ripen and growth changes 

 take place in the accessory organs. This is followed by the 

 period of oestrus proper, during which ovulation takes place (in 

 some species only after copulation), accompanied by further 

 changes, usually of a retrogressive nature, in the accessory 

 organs. It is at this period only, in the lower mammals, that the 

 female will receive the male (but see p. 55). (Estrus is usually 

 followed by a short recuperative period — the metoestrus; sub- 

 sequent events depend primarily on the fate of the ova produced 

 at oestrus and on the species of animal. 



In the absence of pregnancy, the monoestrous animal with 

 only one oestrus per breeding season, returns to anoestrus, 

 usually with an intervening period of development in the ovary 

 and accessory organs. The polyoestrous animal, on the other 

 hand, with a series of cycles in a breeding season, enters upon a 

 very transitory period of development, the dioestrous interval. 

 At the end of this short phase prooestrus supervenes and the 

 cycle starts again. The occurrence of successive oestrous 

 periods with no real interval of rest constitutes a dioestrous 

 cycle, of which the essential feature is that growing follicles or 

 corpora lutea are present the whole time in the ovary. 



After ovulation, conditions in the non-pregnant female are 

 determined by the behaviour of the corpus luteum. This may 

 show only the most transitory development, as in the rat and 

 mouse, or, as in Marsupials and the ferret, it ma}^ undergo 

 development equal or nearly equal to that found during preg- 

 nancy, with very striking growth effects upon the accessory 

 organs. In the latter case the term ' pseudo-pregnancy ' ^ is 



1 This term, coined by Matthews Duncan (172) to indicate a 

 psychological condition in the human female, was applied to the post- 

 ovulation phase in Dasynrus by Hill and O'Donoghue (300), and later 

 to the same phase in the bitch by IVIarshall and Hainan (449). 



