THE INHERITANCE OP FAMILY TRAITS 47 



two (including the girl of 15) are very obese, one normal and 

 one under weight. This result accords with the hypothesis 

 that obesity is due to a defect. It is noted that the mother's 

 mother had a goitre; and it is probable that in this family 

 there is an hereditary deficiency in growth control. 



not obese — not obesecf 



cT 



slender 



cf wt. 275 lbs. 



wt. 180 to 240 lbs. 



not obese? 

 has goitre 



cT, large 



9 , large at 16 — d' 

 wt. 160 lbs. 



9 , slender 



9 , at 15 

 75 kilos 



simple meningitis obese, at 15 months, 36 lbs. 



slender 



Longevity. When Dr. O. W. Holmes was asked for specifi- 

 cations for a long life he advised, in effect, first to select long- 

 lived grandparents. This advice accords with a widespread 

 opinion that longevity is inheritable. But length of life is not 

 a unit character. It is a resultant of many factors; especially 



DtO 



all but one lived ioToorover 



fbf t70 77 



Fig. 18. — A short pedigree (early 19th century in United States) illustrat- 

 ing "inheritance" of longevity. F. R.; Att. 1. 



of those factors that resist causes of death. Such factors are 

 absence of defects of bodily structure, resistance to the com- 

 moner virulent germs of disease, and environmental conditions 

 that maintain at its highest point internal resistance. The first 

 two factors are "inheritable'' and the last remains tolerably 



