448 



F. B. HTJTT 



first-year students who entered the University of Minnesota in the fall of 

 1931. Among these the frequency of spaced upper central incisors was 

 found to be: 



per cent 



In 1842 men 11.5 db 0.72 



In 1526 women 8.7 ± 0.72 



Difference 2.8 ± 1.01 



This difference is 2.78 times its (standard) error and therefore indicates 

 a significantly greater frequency of the condition in males than in females. 

 The figures given must include a number of cases in which the gap was not 



TABLE 1 



Sex distribution of spaced incisors in six pedigrees 



TABLE 2 

 Distribution of spaced incisors in relatives of affected students 



Father affected 



Mother affected 



Both parents affected 



Space in sibs or near relatives but not in either parent 

 No known family history 



NUMBER OF REPLIES 



27 

 13 

 5 

 25 

 28 



hereditary, and from other data it would seem that if these could have been 

 eliminated the difference might have been still greater. 



To those in whom the spaced incisors were noted a questionnaire was sent 

 asking for information about its occurrence in relatives. Out of 112 replies, 

 12 were discarded because of inadequate data and two because the condition 

 arose from missing lateral incisors. The remaining 98 were distributed as 

 shown in table 2. 



There was thus a family history of the condition in 71.4 per cent of the 

 affected persons. Downs (1927) has reported that of eleven cases of "spaced 

 uppers" in which the family history could be traced, only one was negative. 



The general findings from the students' replies, as presented in table 3, 



