HEREDITARY SHORTNESS OF THUMBS 



J. K. Breitenbeciier 

 Univcrsifv of Oklahoma, Norman, Oklahoma^ 



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THE SHORT THUMBED HANDS 



Figure 7. The tip of the normal thumb comes nearly to the first joint of the index 

 finger, but this thumb extends scarcely beyond the knuckle. The thumb-nail is also very 

 short and broad. The inheritance of this trait has been traced for five generations and at 

 least one child of every short thumbed individual had thumbs of this kind. The hands 

 shown above are those of the man designated Abnormal 7 in the article. His hands were 

 taken as a standard in comparing the differences between short thumbed and normal hands. 

 An x-ray photograph of the same pair of hands is shown in Figure 8. 



IT has been about ten years since 

 the writer made the first obser- 

 ' vations upon the abnormahty 

 which is described in this naper, 

 namely a human hand in which the 

 thumb is disproportionately short. 

 During these years information has 

 been collected, whenever the oppor- 

 tunity presented itself, by personal 

 observation. Since the abnormal 

 character has been traced through five 

 generations, it is thought feasible to 

 publish all data at present, rather 

 than to withhold it for further in- 

 formation. 



One sees, upon external examina- 

 tion, a hand that is long and narrow 

 when compared with the normal ; but 



the most clearly distinguishable char- 

 acteristic about this hand is that every 

 individual affected manifests a thick, 

 short thumb with a nail that is very 

 broad and short (about three-quarters 

 of an inch in width and five-sixteenths 

 to three-eighths of an inch in length). 

 To determine the amount of varia- 

 tion in the normal thumb, the writer 

 made outline drawings of palmar 

 views of several hands, consisting of 

 random samples taken from college 

 students and from the normal mem- 

 bers of the short-thumbed family. Each 

 sketch was made by placing the hand 

 on a sheet of paper, and with the aid 

 of a pencil outlining the hand by 

 marking" the outside of each finger. 



^ Contribution from the Zoological Laboratory of the University of Oklahoma, Second 

 Series, No. 28. 



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