82 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93 



with ear troubles as a whole, according to extensive statistics, " the 

 left ear becomes diseased more often than the right ", in the proportion 

 of about 5 to 4 (Biirkner, 1883, p. 103). The significance of this 

 eludes us for the present." In this connection it must not be forgotten 

 that not a few one-side cases tend with time to become bilateral. 



CONSTITUTIONAL DISEASES, LOCAL PATHOLOGICAL CONDITIONS, 

 TRAUMATISMS, IRRITATIONS 



None of these conditions is associated with ear exostoses, except 

 on more or less infrequent occasions. Examinations of osseous ma- 

 terials show that in cases where gout, arthritis, or syphilis have run 

 unchecked to their limits, there are generally no ear exostoses. These 

 diseases, as well as most of the local irritative conditions affecting the 

 external meatus, can occupy no more than a secondary place in the 

 etiology of the abnormal growths. They can probably all be accepted 

 as occasional exciting, but not as the original, causes, except perhaps 

 in the case of certain traumatisms of the bones composing the meatus. 

 The real, the predisposing, cause is different : it is deeper and is gen- 

 eralized over most if not all human groups. 



THE GENERAL CAUSE 



On the basis of the extensive materials reported in this work and 

 after all preceding considerations of the etiology of ear exostoses, 

 both by other authors and the writer, it seems possible now to approach 

 certain generalizations that hitherto were impossible. 



Let us fix our minds once more on the essential facts of the subject 

 under consideration. These are : an apparently complete absence of 

 the process in animals, including the primates ; a generalized predis- 

 position to it in recent and present man ; the absence or rarity of 

 developmental defects; the predominance of the manifestations from 

 the post-pubertal to presenile time of life ; the excess of involvement in 

 the males ; the marked tendency of the growths to bilaterality and even 

 symmetry ; and their ascertained occasional direct inheritability. 



All this, as seen in previous discussion, points to the conclusions 

 that ear exostoses constitute a special complex or entity belonging 

 not in the field of diseases but in that of abnormalities, and that they 

 must be directly connected with neuro-vascular derangements, which 



"Here again, curiously, the serious defect of ear atresia forms an exception, 

 being considerably more common, especially in the American Indian, on the 

 right side. 



