THE INHERITANCE OF 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 



cf wt. 275 lbs. 



not obese? 

 has goitre 



slender 



wt. 180 to 240 lbs. 



cT, large 9 , large at 16 — c?" 

 wt. 160 lbs. 



— r~ 



9 , slender 



9 , at 15 

 75 kilos 



simple meningitis obese, at 15 months, 36 lbs. 



1 

 slender 



Longevity. When Dr. 0. 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 



DrO 



n 



t9i 



t82 



r over IJ LJ I I 



tW +70 77 



bU but one lived to 70 or over 



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 ''inlieritable" and the last remains tolerably 



