NO. 6 EAR EXOSTOSES HRDLICKA 33 



The single tumefaction-exostosis is, as a rule, the initial stage, but 

 a second enlargement, generally from the opposite side of the tympanic 

 portion, will soon follow, the third and perhaps additional growths 

 developing later. 



In no less than 6 of the 12 Indian series the percentage of single 

 tumors is practically identical. 



In three of the remaining groups, Peru, Virginia, and Kentucky, 

 and in both Polynesian groups, the proportion of cases with two or 

 more growths is exceptionally high. 



The Peru and the Kentucky material especially shows many ears 

 with three exostoses. 



Two notes of caution are here necessary: i, In some specimens 

 with one ear exostosis, had the subject survived to older age there 

 might have taken place a development of additional growths ; and 2. 

 where the canal is nearly filled by one. two, or three exostoses, other 

 growths, smaller and more posterior, cannot be seen and thus escape 

 enumeration. This means that the proportions of cases with more than 

 one exostosis would be somewhat higher were we dealing with those 

 who lived their full span of life ; and that the proportions of two and 

 especially those of three or more growths are in reality in some 

 measure higher than those given in the records ; but the excesses in 

 either case could hardly be very material. 



The chief meaning the above results convey is once more that the 

 ear atifection under consideration appears in the form of an entity or 

 " diathesis ", which manifests itself practically identically in a large 

 proportion of dififerent geographic or tribal -groups of the same race, 

 but which may also, through some i)eculiar causes, dift'er substantially 

 in other groups of the same people. 



LOCATION 



As in other respects, so in this also there are in the history of 

 ear exostoses some variants of experience and hence of opinion. 

 According to Toynbee (i860), ear exostoses 



may develop in any part of the length of the tube; but the part from which 



they most commonly originate is about the middle third of the passage 



Occasionally the posterior wall affords the point of origin to the tumour, and 

 then it not unfrequently resembles a simple bulging of the wall. In other cases, 

 a similar tumour is also developed from the anterior part, and the two protuber- 

 ances meet and lie in contact in the middle, leaving an inferior and superior 



triangular space at the place of the original opening of the tube The 



tumour may grow from the upper surface of the tube Two or more 



tumours, again, extend sometimes from various parts of the circumference of 

 the meatus, and converging towards the center, fill up nearly the whole cavity. 



