THE INHERITANCE OF FAMILY TRAITS 167 



that the ''nervous temperament" may be largely responsi- 

 ble for disordered digestion by disturbing the ordinary secre- 

 tory functions. So, likewise, it is probable that there are 

 family characteristics which favor peculiarities of the hver 

 resulting in its abnormal functioning. Especially jaundice 

 and gout may have hereditary basis. An example of family 

 pedigrees with high incidence of dyspepsia and more specific 

 alimentary troubles is given in Fig. 146. 



T dysentery 



tho 



rhronirl ^-' + '^3, cancer 

 i«in Of liver 



digestion storoacli LJ W ■ Lj LI ^ 



Fig. 146 Fig. 147 



Fig. 146. — Pedigree of digestive weakness. F. R.; She. 1. 



Fig. 147. — Pedigree of diabetes mellitus (black symbols). In this case 

 the parents of affected offspring are not themselves affected; the trait is due 

 to the absence of something that is present in normal persons. Bramwell, 

 1908, p. 265. 



a. Diabetes Insipidus.^ — This term has been applied to 

 the symptoms of passing large amounts of greatly diluted 

 urine. The affected persons have to drink much water to 

 meet the rapid drainage through the kidneys. Numerous 

 families are known that show this peculiarity in several close 

 blood relatives. The typical condition is that two unaffected 

 parents, even of diabetic strains, will have only normal chil- 

 dren; diabetic offspring have at least one diabetic parent. 

 This would indicate that diabetes is due to a positive factor 

 (Fig, 148). Nettleship (1910) points out that age of incidence 

 tends to diminish in successive generations. 



^ The hereditary behavior of diabetes mellitus or "sugar in urine" has 

 been less studied. (Fig. 147). 



