Discussion 81 



parent. Amyloidosis in mice is a disease with maximum incidence in 

 middle age. Incidence falls to zero in later life. Thus it resembles 

 some diseases in man, particularly some liver diseases. If a single 

 X-ray dose is given to the young animal, this whole sequence is 

 moved to the left on the time axis so that a given incidence of 

 amyloidosis is seen at an earlier age, and about the same total 

 incidence is seen. 



Perks: I was also struck by the symmetry of the curves of distri- 

 bution of onset of the different lesions in your rats, Dr. Berg. We 

 should bear in mind that when you combine symmetrical curves of 

 this kind and get a curve of onset of lesions of all kinds, you do not 

 necessarily reproduce symmetry. Further, as the mean delay 

 between onset and death is significantly different for the different 

 lesions, the final death curve could well be highly skew as compared 

 with the component symmetrical curves of onset. 



The other point I was particularly interested in was the delay in 

 onset for females. My mind always goes to the question of the useful- 

 ness of statistics, and in the life assurance world we are seriously 

 concerned with the differential mortality between males and females, 

 particularly in view of the growing volume of pension business. In 

 this country there is a difference of about five years in effective age 

 between males and females at the older ages. In some of the Scandi- 

 navian countries there is a considerably narrower difference and the 

 mortahty for males is much lower than in this country. We actuaries 

 do not really know why male and female mortalities differ, nor do we 

 know why the Scandinavian male mortality is much more favourable 

 than in this country, although some of us have thought in terms of 

 environmental factors. It does seem to me that there may be some 

 clue in the figures given here today. If, in fact, there is delay in the 

 onset of some of these degenerative diseases in females as compared 

 with males, maybe the answer is essentially constitutional. 



Jalavisto: In Finland the excess of male over female mortality 

 is about the highest in the world, especially in the 50-year-old group. 

 This seems to be because coronary death is so common in Finland. 

 I have the impression from Finnish data that at that age or in that 

 sex which has a greater disposition for a certain disease, it is very 

 difficult to lower the mortality in that disease by improving external 

 conditions. For example, in cholecystic diseases in which females 

 have a higher mortality than males, the reduction which has taken 

 place in recent years is greater in the male — although in most 

 diseases the reduction is much greater in females. 



Perks: When I mentioned the Scandinavian countries I was not 

 thinking so much of Finland as of the Netherlands, Denmark, 



