I.— PHYSIOLOGY. 181 



The ovary does not function till puberty and there is considerable 

 evidence to show that this is brought about by some internal stimulus. 

 A young ovary grafted into an adult male or female will begin its secretion 

 sooner than its age warrants, whilst an adult ovary engrafted into a young 

 animal will not function until the animal reaches maturity. This fact 

 is of practical importance, since in cases of infantilism it is not necessarily 

 the ovaries which are at fault and ovarian transplantation may not 

 improve the patient. 



The literature contains plenty of examples of the beneficial effect of 

 ovarian transplantation, both in men and animals. For example, a bitch, 

 aged 17 years, after an endoperitoneal transplantation showed rejuvena- 

 tion, sexual activity, and gave birth to five normal puppies. Bell analyses 

 118 cases of ovarian grafting, and states that menstruation was possible 

 in 107 cases of these, and occurred in 71. The ovary differs from other 

 organs of internal secretion in that it functions in a cyclic manner, and 

 it is obvious that extracts made from ovarian tissue may exert a different 

 action according to the period of the cycle when they are made. 



Numerous extracts have been prepared from the ovary which are 

 reputed to exert one or other type of action. 



' Oestrin ' is the name given to one such substance : it can be made 

 from many sources, both animal and vegetable, besides the ovary. Oestrin 

 exerts a very definite action in lower animals, but its use in man is so 

 variable and disappointing as to make it valueless in practical medicine. 

 When it is injected subcutaneously into spayed rats and mice it produces 

 typical oestrus with normal sex instincts, and when injected into immature 

 animals it induces puberty ; regular injections at fixed intervals will keep 

 animals sterile. 



Many experimental observations show that the corpus luteum is 

 concerned with the rhythm of the oestrus cycle and with the prevention 

 of ovulation. A persistent corpus luteum, both in the case of animals 

 and women, produces sterility, a condition which is cured by its removal. 

 The presence of fully formed corpora lutea appears to inhibit some ovarian 

 secretion, and this condition obtains in animals for a time between the 

 heat periods, but more particularly during pregnancy. In women there 

 is plenty of pathological evidence to show that functional corpora lutea are 

 not present during menstruation. 



If the corpora lutea exert this controlling action on ovarian function, 

 then their removal should release the normal ovarian function ; such 

 operations during pregnancy are invariably followed by abortion. On 

 the other hand, injections of properly prepared corpus luteum prevent 

 ovulation ; this has been shown in the case of the hen, the rabbit, and 

 the guinea-pig. 



Interstitial Hormone. 



A third active substance distinct from oestrin and corpus luteum is 

 elaborated from the ovary and was described by Marshall and myself. 

 This substance is water-soluble and thermo-stabile, and can be prepared 

 from the ovary at one stage of its cycle only, by maceration with warm 

 saline followed by boiling and filtering. The injection of this substance 

 into animals causes a secretion of pituitrin, and this in turn renders the 



