THE OVARY AND ITS IMPORTANCE 53 



8. Number of eggs produced by different vertebrate ovaries 



9. Spontaneous and dependent ovulation in the mammals and in other vertebrates 



10. Egg viability after discharge from the ovary 



11. History of the egg follicle after ovulation 



a. Follicles which do not develop a post-ovulatory body 



b. Follicles which develop a post-ovulatory body; formation of the corpus luteum 



12. Hormones of the ovary and their activities in effecting the reproductive condition 



a. Estrogenic hormone 



1) Definition and source of production 



2) The ovary as the normal source of estrogen in the non-pregnant female 



3) Pituitary control of estrogen formation 



4) Effect of estrogen upon the female mammal 



5) Effects of estrogen in other vertebrates 



b. Progesterone — the hormone of the corpus luteum 



1 ) Production of progesterone 



2) Effects of progesterone 



F. Reproductive state and its relation to the reproductive cycles in female vertebrates 



1. Sexual cycle in the female mammal 



a. Characteristics and phases of the reproductive cycle 



b. Relation of estrus and ovulation in some common mammals 



1) Spontaneously ovulating forms (Sexual receptivity of male occurs at or 

 near time of ovulation) 



2) Dependent ovulatory forms (Sexual receptivity [heat] occurs previous to 

 time of ovulation) 



c. Non-ovulatory (anovulatory) sexual cycles 



d. Control of the estrous cycle in the female mammal 



e. Reproductive cycle in lower vertebrate females 



G. Role of the ovary in gestation (pregnancy) 



1. Control of implantation and the maintenance of pregnancy in mammals 



2. Gestation periods, in days, of some common mammals 



3. Maintenance of pregnancy in reptiles and other vertebrates 

 H. Role of the ovary in parturition or birth of the young 



I. Importance of the ovary in mammary-gland development and lactation 

 J. Other possible developmental functions produced by the ovary 

 K. Determinative tests for pregnancy 



A. The Ovary and Its Importance 



One of the editions of the treatise on development, "Exercitationes de 

 Generatione Animalium," by William Harvey (1578-1657) contains a pic- 

 ture of Jupiter on a throne opening an egg from which various animals, 

 including man, are emerging (fig. 25). Upon the egg (ovum) are engraved 

 the words "ex ovo omnia." At the heading of chapter 62 of this work Harvey 

 placed a caption which explains the phrase ex ovo omnia more explicitly. 

 This heading reads: "Ovum esse primordium commune omnibus animalibus" 

 — the egg is the primordium common to all animals. Published in 1651, this 

 statement still maintains its descriptive force. 



Many individual animals arise by asexual reproduction, that is, through 

 a process of division or separation from a parent organism. In the phylum 

 Chordata asexual reproduction is found among the Urochordata, where new 



