THE FUNXTIOX OF (ESTRIX 123 



months. Immediately ovulation takes place and the corpora 

 lutea are formed an entirely new phase of growth is initiated. 

 A large mass of work begun by Fraenkel (208-9) and extended by 

 Ancel and Bouin (30-2), Loeb (400 ), Marshall (444), and Ham- 

 mond (264), shows fairly definitely that the corpus luteum 

 itself controls the changes of the post-oestrous phase b}' some 

 specific internal secretion distinct from that associated with the 

 production of oestrus. This work is dealt with in Chapter X, but 

 one further point may be mentioned here. Functional correla- 

 tion suggests that the corpus luteum and the oestrus-producing 

 substance are to some extent antagonistic. The injection of the 

 oestrus-producing hormone during pseudo-pregnancy will over- 

 ride this stage of the cycle and result in the reappearance of 

 oestrus. In the same way its injection during pregnancy has 

 been shown to lead to abortion or reabsorption of the foetuses. 

 If the apparent antagonism between the oestrus-producing sub- 

 stance and the corpus luteum is a genuine effect, it is difficult 

 to see how the one hormone can control the whole of the 

 fertile cycle. 



The controversy about the limitations of the action of oestrin 

 therefore centres round three problems: 



ia) Is oestrin responsible for the pre-pubertal development of 

 the accessory organs before the first oestrus? 



(h) Is oestrin responsible for the post-ovulation changes in the 

 vagina, uterus, and mammary glands? 



(c) What is the significance of the abundance of oestrin in the 

 placenta and body fluids during pregnancy? 



These problems are discussed below. 



[d) ATTAINMENT OF PUBERTY 



It has been pointed out above (p. 20) that the attainment of 

 puberty consists of two phases; the gradual pre-pubertal growth 

 of the accessory organs and the sudden appearance of the first 

 oestrous period. There is clearly no reason to distinguish 

 between the causative mechanism of this first oestrous period 

 and that of any subsequent one. The underlying mechanism 

 must be the same, although it is operating for the first time at 



