I06 VERTEBRATE REPRODUCTIVE CYCLES 



I.C.S.H. The interstitial-cell-stimulating-hormone secreted 

 by the anterior lobe of the pituitary gland. 



L.H. The luteinizing-hormone which is apparently the same 

 substance as I.C.S.H. 



Luteinization. The process of differentiation by which the cells 

 of the ovarian follicle are transformed into those of the 

 corpus luteum. 



Menstrual cycle. The oestrous cycle of the higher monkeys and 

 apes. It is characterized by a period of bleeding from the 

 uterus at the end of each cycle, and in one species (man) it 

 has an average periodicity of about a month. 



Menstrual period {menstruation). That period at the end of a 

 menstrual cycle when the uterus is reduced in size and 

 when bleeding occurs. 



Migration. The annual movement of animals to another locality 

 in order to breed there, and the annual return when the 

 breeding season is over. 



Mitogen. A hormone which acts as a general mitosis stimulator, 

 and which, according to its influence on vaginal growth or 

 on comb growth in capons, can be further classified as an 

 oestrogen or an androgen. 



Monoestrous. Having only one oestrous period each year. 



Oestradiol. The main hormone secreted by the ovary. 



Oestrogen. A hormone (e.g. oestradiol) secreted primarily by 

 the ovary, or a substance with similar physiological 

 properties prepared artificially. 



Oestrous cycle. The sequence of changes in the reproductive 

 system of a female mammal, namely pro-oestrus (period 

 of increasing activity), oestrus (when the female is ready 

 to mate and when the eggs are shed from the ovary), 

 metoestrus (period of declining activity), and dioestrus 

 (period of quiescence). 



Oestrus. The period when a female mammal is sexually aroused, 



when copulation occurs, and when the eggs are shed from 



the ovary. 

 Oviductin. A hormone which, it is suggested, may be secreted 



by the pre-ovulation corpora lutea of the bitterling, and 



perhaps also of other lower vertebrates. 



Ovulation. The release of the eggs from the ovary. 



Poly oestrous. Having more than one oestrous period each year. 



Progesterone. The hormone secreted by the corpus luteum of 



the marsupial and eutherian mammals. 

 Puberty. The time when an animal is first able to reproduce. 



