Ageing in Inbred Strains of Animals 123 



graft can be followed from day to day with the aid of vaginal 

 smears. The various aspects of the transplantation of the 

 ovary have been exhaustively discussed by Krohn (1955). In 

 our own experiments with subcutaneous transplantation of 

 ovaries into ovariectomized females, a completely normal 

 oestrus cycle was found which lasted in most cases nearly as 

 long as in the animal with the ovaries in situ (Boot, 1956). 

 Complete normal hormonal function could also be proved by 

 successful transfer of fertilized ova into the animal with the 

 subcutaneous transplant. 



The technique of organ transplantation can also be used 

 for the study of differences in ageing processes of organs in 

 different inbred strains. For instance, when we transplant 

 ovaries of two inbred strains to their F x hybrid, and thus to 

 the same environment, we can determine which ageing pro- 

 cesses are inherent in the ovary itself and which are dependent 

 on changes in other organs, e.g. in the hypophysis. 



There is one point which has, however, to be taken into 

 consideration, when we transplant tissues or organs from an 

 animal of an inbred strain to an F x hybrid: i.e. the possibility 

 that the tissues may change in the new host by adaptation or 

 mutation. This change has been found by Barrett, Deringer 

 and Hansen (1953) with transplants of malignant tumours 

 from inbred strains to F x hybrids. 



Another question which can be investigated with trans- 

 plantation experiments is that of the lifespan of the different 

 organs. Experiments with old ovaries transplanted into 

 young animals showed that a prolongation of the hormonal 

 function is not possible far beyond the ordinary lifespan of the 

 ovary. 



Similar approaches are possible for other organs, although 

 it must be borne in mind that not all transplantations are as 

 successful as those with ovaries. 



Transplantations of the testes are only successful when the 

 transplanted testes are taken from 3-day-old animals. More 

 adult testes, even when stripped from their connective tissue 

 capsule, show after transplantation no functional activity. 



