THE INHERITANCE OF FAMILY TRAITS 151 



xinderwent a slow atrophy starting as early even as the 

 tweKth year. The method of inheritance in this family is 

 striking. Only males are affected and they, as well as the 

 unaffected females, may transmit the defect; but unaffected 

 males have no affected children. Femaleness in this family 

 is incompatible with atrophy. (Fig. 125). 



^ 



Op 4[^ (!)p D^ 



■o 



N N N N 



Fig. 126. — Pedigree of a family of tremblers. Affected persons (black 

 symbols) are derived from at least 1 affected parent, and 2 normal parents 

 have only normal offspring. Trembling is thus due to the presence of a spe- 

 cial character. From Deboke and Rbnaitlt, 1891. 



c. A family of tremblers has been recorded by Debore 

 and Renault. In this family all normals produce only normal 

 offspring while two affected parents may have a normal 

 child. The pedigree deserves no great stress since details 

 are lacking (Fig. 126). 



d. Hernia. — Man's erect position is accompanied by 

 physical dangers from which his quadruped ancestors were 

 free, for in man the weight of the viscera has largely to be 

 borne by the pelvis and lower abdominal wall. The erect 

 position has subjected the muscles of the inguinal region to 

 a peculiarly rigorous test. They often fail and an inguinal 

 hernia is the result. Such hernias usually are consequent to 



