142 P. L. Kroiin 



The ovary is a composite organ, some of whose cells undergo 

 cyclic changes similar to and in fact responsible for the changes 

 in the mammary glands and uterus. The other main group of 

 cells, the oocytes, may, as will be seen later, behave rather 

 like some neurones. Their lifespan may indeed rival that of 

 neurones, although the chance that any particular oocyte will 

 survive as long is much less. It is about the age changes in 

 the ovary and the ways in which the methods of tissue trans- 

 plantation can be used to study the changes that I wish to 

 talk today. 



The Life of the Ovary 



Temporal changes in the sensitivity of the ovary to its 

 hormonal environment 



(a) During intra-uterine life and before puberty 

 A discussion of the process of ageing in the ovary cannot 

 be restricted to the adult or old organ but must also consider 

 the changes that take place during the prepubertal period. 

 The ovary can, indeed, be permanently affected by its hor- 

 monal environment very early in intra-uterine life. It is 

 generally believed, for instance, that the ovary of the free- 

 martin female cattle twin develops abnormally because it is 

 affected by the transplacental passage of hormones from its 

 brother. The gonads of a foetal foal may, at one stage, be 

 twice the size of the ovaries of the parent (Amoroso and 

 Rowlands, 1951). This enlargement, due mainly to an increase 

 in the amount of interstitial tissue, is attributed to the effects 

 of oestrogen rather than gonadotrophin because it occurs 

 during the latter part of pregnancy, when the serum gonad- 

 otrophin levels characteristic of the earlier stages have fallen, 

 and because serum gonadotrophin does not cross the placental 

 membrane. Bacsich (1949, 1950) has demonstrated regressive 

 changes in the human ovary just after birth which he relates 

 to tlie withdrawal, at the time of delivery, of a hormonal 

 stimuhis. Like the adrenal cortex, therefore, to which it is so 



