150 P. L. Krohn 



mechanisms of ccstrous behaviour which ensure mating only 

 near the optimum time in animals do not operate in human 

 beings. 



Transplantation Techniques Applied to the Study 

 of the Ageing of the Ovum and Ovary 



The method of tissue transplantation has been used for the 

 study of a wide range of biological problems. The next part of 

 this paper will discuss how the technique has been applied 

 to the particular problems presented by the ageing ovum and 

 ovary. Finally, some of the general hazards that beset the 

 tissue transplanter, the ways of overcoming them, and some 

 experimental results will be described. 



The transfer of ova 



The technique for the collection of fertilized ova from the 

 Fallopian tubes and their transfer to either the tubes or the 

 uterus of another animal is now well established and has been 

 used especially in the study of reproductive physiology in 

 rabbits and cows; such experiments have not usually, however, 

 been directed towards the study of age changes in the repro- 

 ductive tract itself. The method has also been used by Fekete 

 (1947) to investigate the effect of transferring ova from one 

 strain of mice into an environment provided by another strain 

 of mice. Her work shows, for example, that the eggs of the 

 two strains, dba and C57, have about equal powers of survival 

 but that the environment provided by one strain is more 

 conducive to survival than that provided by the other. Once 

 again, however, the work was not directed towards the study 

 of age change but it indicates the potentialities of the method. 



The grafting of whole ovaries 

 The onset of puberty 



Some of the earliest work using ovarian transplantation 

 was concerned with the factors which influence the onset of 

 puberty. It was, indeed, carried out long before an interpre- 

 tation of the results in terms of pituitary gonadotrophin 



