154 BIOLOGY OF DEATH 



this rather highly fertile group of people, belonging in 

 the main to a period when restrictions upon size of family 

 were less common and less extensive than now. In the 

 second place, the female l x curve is actually convex to 

 the base throughout a considerable portion of middle 

 life whereas, normally, this portion of the curve presents 

 a concave face to the base. 



Apart from these deviations, which are of no partic- 

 ular significance for the use which Bell makes of the 

 data, the Hyde material is essentially normal and simi- 

 lar to what one would expect to find in a random sample 

 of the general population. In this material there were 

 2.287 cases in which the ages at death of the persons and 

 the ages at death of their fathers were known. It occurred 

 to Bell to arrange this material in such a way as to 

 show what, if any, relation existed between age at death 

 of the parent and that of the offspring. He arranged 

 the parents into four groups, according to theiage at which 

 they died, and the offspring into five groups upon the 

 same basis. In the case of the parents the groups were : 

 First, those dying under 40 ; second, between 40 and 60 ; 

 third, between 60 and 80 ; and fourth, at age 80 and over. 

 The groups for the offspring were the same, except that 

 the first was divided into two parts, namely, those dying 

 under 20 and those dying between 20 and 40. The result- 

 ing figures are exhibited in Table 14. 



The results for father and offspring are shown in 

 Figure 42, based upon the data of Table 14. In each 

 of the 5 polygons, one for each offspring group, the first 

 dot shows the percentage of fathers dying under 40; 

 the second dot the percentage of fathers dying between 

 40 and 60 ; and so on, the last dot in each curve showing 

 the percentage of fathers dying at age 80 and over. It 



