SEX DIFFERENCES IN HUMAN DENTITION 



449 



confirm the other evidence that the gap is less common in women than in 

 men. 



If there were no sex difference in the expression of this character, the num- 

 bers and percentages in these four classes should be approximately equal in 

 the two sexes. That they are not so in the 95 students who replied to the 

 questionnaire can hardly be considered more indicative of a sex difference 

 than of a tendency for college boys to answer their professors' questionnaires 

 more faithfully than do college girls. However, the fact that among 50 



TABLE 3 



Sex distribution of spaced incisors 



(A) Sex distribution in affected persons: 



1. In 50 affected parents 



2. In 95 affected students of known sex 



(B) Percentages of each sex affected: 



3. In 70 sibships with family history:* 



(a) in 86 males 



(b) in 83 females 



4. In 45 sibships from affected parents* 



* Excluding the propositus in every sibship. 



TABLE 4 



Width of gap between spaced incisors 



affected parents nearly twice as many fathers had the condition as did 

 mothers corroborates the other evidence that the character is sometimes sup- 

 pressed in females. 



Since the sex ratio of replying students is so abnormal (63 : 32) these stu- 

 dents cannot be used in any determination of the incidence of spaced incisors 

 in their sibships. Accordingly in class B 3 of table 3 there have been included 

 only the brothers and sisters of those students who reported the condition in 

 either parent or in some near relative. This is an adaptation of the "brother 

 and sister" method introduced by Weinberg (cited from Baur, Fischer and 



