X \- 1 1 



MAN 



201 



The inheritance of this pccuharit\- has been carefully 

 i n vest iL;a ted !)>• Dr. iJrinkwater, who collected all the 

 data he was able t(j find anioni; the members of a 

 larLTo famih- in which it occurred. The result is the 

 pedi<4i-ee shown on p. 202. it is assumed that all 

 who are recorded as havini^ offspring were married 

 to normals. Examination of the pedii^ree brinies 

 out the facts ( l) that all affected individuals have an 

 affected parent ; (2) that none of the unaffected in- 



^mmm 



Rairiof^r.ipl) of a lnai liyilactyluu^ li.iinl. 



di\iduals, thoui;h sprunj^^ from the affected, ever 

 have descendants who are affected ; and (3) that in 

 families where both affected and unaffected occur, 

 the numbers of the two classes are, on the averai^c, 

 equal. (The sum of such families in the complete 

 l)ediL;rec is tiurty-ninc affected and thirt\'-si.\ normals.) 

 it is obvious that these are the conditions which are 

 fulfilled in a simple Mendelian case, and there is 

 nothini;: in this pediLiree to contradict the assertion 

 that brach\'dactyl\', whatever it may be due to, 



