Age Changes in the Ovary 147 



Writrht only counted follicles over 0-3 mm. in diameter and 

 therefore omitted all the smaller follicles which make up 

 90-95 per cent of the total population. 



The Age of Ova at the Time of Ovulation and the 

 Problem of Oogenesis 



It is becoming increasingly clear that the age of the mother 

 at the time of ovulation may affect the future characteristics 

 of the offspring in all sorts of ways. Since most of the evidence 

 bearing on this point has been brought together in a sj^mpos- 

 ium organized by the New York Academy of Sciences (1954) 

 there is no need to do more than mention a few examples. 

 The increased risk of giving birth to a Mongol child when the 

 mother is more than forty years old has long been recognised. 

 The defect, whatever its cause, seems to be related to the age 

 of the mother only and not to the number of pregnancies 

 that she has had. The chances of finding a wide range of 

 embryological defects and the susceptibility of animals to 

 neoplastic disease are also related to the age of the mothers 

 (Strong, 1954; Law, 1954). 



The relative significance of, on the one hand, the ageing 

 ovum in the ovary, and the ageing uterine environment on 

 the other, cannot yet be decided. It remains important, there- 

 fore, to determine whether the ovum that is fertilised should 

 be regarded as a young or an old cell. We are thus led immedi- 

 ately to consider the problem of oogenesis, which has formed 

 one of the major points of controversy among reproductive 

 physiologists for a very long time. 



Two entirely contrary views have taken it in turn to become 

 the accepted dogma. The older view is that the ovary is 

 endowed during embryonic development with a fixed number 

 of primordial germ cells from which the oocytes subsequently 

 develop. These cells are not derived from the germinal 

 epithelium which covers the ovary, but migrate to the ovary 

 before birth. Multiplication by ordinary mitosis may occur 

 during intra-uterine life but has come to an end soon after 

 birth; from then on the ovary merely uses up the material 



