108 THE VERTEBRATE OVARY AND ITS RELATIONSHIP TO REPRODUCTION 



of the gestational period, e.g., rat, rabbit, dog, etc. In other species, such as 

 the human, mare, etc., the placenta through its ability to duplicate the pro- 

 duction of the ovarian hormones, assumes a role during the latter phase of 

 pregnancy. (For further details, consult Folley and Malpress in Pincus and 

 Thimann, '48; Selye, '48, pp. 828-832; and Turner, '48, pp. 428-448.) 



In the dog or opossum during each reproductive cycle, the mammary glands 

 are stimulated to grow and may even secrete milk (dog). These changes 

 closely parallel the ovarian activities, particularly the luteal phase of the cycle. 

 In the human, functional growth changes occur in pregnancy, but, pending 

 the events of the ordinary cycle, alterations in the duct system are slight al- 

 though the breasts may be turgid due to increased blood flow and connective- 

 tissue development. 



J. Other Possible Developmental Functions Produced by the Ovary 



As the eggs of the opossum and rabbit travel through the uterine (Fal- 

 lopian) tube toward the uterus, they are coated with an albuminous, jelly-like 

 coating. Similar jelly coatings are added to the eggs of the bird, reptile, frog, 

 toad, and salamander. These coatings or membranes added to the egg as it 

 travels through the oviduct are known as tertiary egg membranes. 



In the toad, the secretion of the protective jelly by the oviduct can be 

 elicited by the lactogenic hormone present in beef pituitary glands. The se- 

 cretion of the albuminous jelly coatings around the eggs of frogs, salamanders, 

 reptiles, and birds may be related to this hormone. The formation of the 

 crop milk of pigeons has been shown by Riddle and Bates ('39) to be de- 

 pendent upon the presence of the lactogenic hormone. 



The function of the ovary in influencing the outflow of the lactogenic hor- 

 mone from the pituitary, if present in the above cases of glandular secretion, 

 must be an indirect one. Evans and Simpson in Pincus and Thimann ('50) 

 ascribe the outflow of the "lactogenic hormone (luteotrophic hormone)" of 

 the mammalian pituitary to estrin produced by the ovary. It is possible that 

 in the salamanders, frogs, toads, and the birds an indirect ovarian influence 

 may similarly induce secretion of the lactogenic hormone which in turn gov- 

 erns the elaboration of the albuminous jelly deposited around the egg in 

 transit through the oviduct. 



K. Determinative Tests for Pregnancy 



Various tests have been used to determine the probability of pregnancy 

 in the human female. These tests are discussed in Chapter 22. 



