48 



A NEW TYPE OF BRACHYPHALANGY IN MAN. 



taken in its old uncritical sense. But the author has trusted in second- 

 hand information and also characterized as "not brachyphalangous" 

 several members of the family, in which the character manifests itself 

 under another somatic type, ''doigt crochu" (cf. p. 12). 



A case so extreme as that of 1151.2 9 S. G., discussed above, might 

 be comparatively rare. But the frequent occurrence of very slight 

 shortening of the affected phalanx in the heterozygous individuals in 

 our material makes it clear how absolutely insufficient and misleading 

 second-hand information is in heredity work in man. 



We are here dealing with a malformation, in many individuals better 

 defined, simpler, and therefore more easily controlled than most of the 

 hereditary characters hitherto studied in human material. Here, if 

 anywhere, it might a priori seem probable that inquiries directed to 

 the family members would furnish a trustworthy basis for the study 

 of the heredity of the malformation. Yet such a method of investiga- 

 tion would have led to entirely false results. In fact, almost none of 

 the B-type individuals would have been recorded, though they are as 

 numerous as the B !-type ones. A pedigree of the descendants of 

 11.5 cf C. A. B. H. as it would have looked if based on the information 

 obtained from family members and examination only of the reported 

 brachj^halangous ones, is given in text-figure 2 as an illustration. 



9(^f d^^d^^^d'^ 



f-f cf d* d" 



Cfp REPORTED TO BC NORMAL 



## REPORTED TO PE BRACHYPHALAN60US 



Text-figure 2. — Pedigree of the descendants of 11.5 c? constructed on basis 

 of information obtained by the members of the family. 



The quite unsatisfactory nature of the material upon which Rabaud 

 principally founds his criticism is obvious in the light of such a pedi- 

 gree. 



When a personal examination of all family members has shown the 

 complete inadequacy of the "second-hand" method of collecting data, 



