PHYSICAL CHARACTERS IN MAN 123 



various organs to the toxin. Davenport considers 

 that pellagra is probably communicable, but the 

 history of the disease will depend entirely upon the 

 constitutional conditions of resistance which it meets 

 in the organs of the body. When both parents are 

 susceptible to the disease, nearly half the children are 

 susceptible, while the disease affects less than i per 

 cent, of the whole population (statistics from Spartan- 

 burg Co., South Carolina). The high incidence in 

 certain strains will, then, be due partly to infection, 

 but also depends upon susceptibility, for susceptible 

 and non-susceptible children often occur in the same 

 family. Pellagra thus bears certain resemblances, 

 from an inheritance point of view, both to tuber- 

 culosis and cancer, and perhaps also to leprosy. 



It was formerly widely held (Sedgwick, 1863) that 

 leprosy was hereditary, but that it descends by 

 collateral lines, and frequently skips a generation. 

 There is probably some basis for this view, which 

 deserves careful attention from modern students of 

 this disease. The lepra bacillus is known, just as 

 is the tubercle bacillus, but there may be constitu- 

 tional differences in the resistance to its attacks. 



vSeveral other pedigrees showing sex-limited in- 

 heritance may be cited from a large mass of data 

 furnished by Sedgwick (1863). Pityriasis versicolor, 

 a skin disease, is confined to the males, but transmitted 

 by the females to their children in a family where the 

 grandfather, his three sons, and nine males of the next 

 generation all have it. In another family numerous 

 warts on the hands characterise the female line for 

 two generations, the mother and her three daughters 

 having them, the two sons normal. 



In another family numerous sebaceous tumours 

 on the scalp occurred in a mother, her daughter, 

 and granddaughter, while the sons were free. The 

 brother's daughters, however, have them, '* as well 



