NO. 6 EAR EXOSTOSES— HRDLICKA 8l 



are more infantile, less differentiated, organically more conservative; 

 the males more advanced morphologically, less set, more variable. 

 For these reasons the effects of any evolutionary belatedness in ac- 

 commodation of parts could confidently be expected to show more 

 in the males. This seems likely to be the explanation of the sex differ- 

 ence in the incidence of the abnormal conditions under consideration. 

 There may be assumed, in general, a somewhat greater control of 

 the normal conditions of the tympanic bone and the external meatus 

 as a whole in the females. 



An interesting fact in this connection is that according to pro- 

 longed observations by otologists, ear troubles and diseases in general 

 are more common in the males than in the females. There is however 

 one notable exception and that is atresia or congenital defect of the 

 external meatus; this serious agenetic defect is considerably more 

 common in the females, particularly in certain human races." 



SOCIAL STATUS 



A number of authors, it has been seen, have voiced the opinion 

 that, among the Whites at least, ear exostoses occur predominantly 

 in the well-to-do classes. If this is so — and there is no voice to the 

 contrary — the question would arise, what is there in the wealthier 

 class that favors the abnormalities ? 



Here is a promising line of inquiry, but the foundations for it need 

 to be strengthened. All that may be said now is that being " well- 

 to-do " means, on one hand, usually more leisure and what this carries 

 with it, on the other hand, a greater preservation of the weaker — which, 

 together, may conceivably lead in time to some weakenings or derange- 

 ments of the basic neuro-vascular controls of different parts of the 

 organism. 



SIDE 



In materially over one-half of the cases of ear exostoses, on the 

 average, the affliction is bilateral and frequently more or less sym- 

 metrical. This points strongly to the conclusion that the basic cause 

 of the growths lies centrally in the nervous system. That not all cases 

 are bilateral is due probably to developmental differences of the bones 

 of the meatus in the two ears. It is well known that no two bones are 

 exactly equal, macroscopically and microscopically, on the two sides. 



In the unilateral cases, there is perceptible a general tendency for 

 the exostoses to be more frequent in the left ear. In clinical experience 



"See the writer's report on the condition, Amer. Journ. Phys. Anthrop., 

 vol. 17, no. 3, 1933. 



