NO. 6 EAR EXOSTOSES HRDLICKA 47 



that would suggest malignity, and on the other in the lack of a 

 substantial basis for any definite subdivision of the growths into dif- 

 ferent classes. 



A case of a pedunculated exostosis operated upon and studied by 

 Politzer (1902, p. 210), " showed here and there very compact lam- 

 ellae (eburnation) with spaces that contained but few vessels." 



Another pedunculated exostosis was removed and studied by Tod 

 (1909, p. 77) who reports briefly as follows: " On making a section 

 the ossification was seen to be proceeding from the centre." Other 

 exostoses " were very hard, with a very thin layer of skin over them." 



A number of detailed histological examinations of ear exostoses are 

 reported by Dahlstrom (1923, pp. 215-216). and notes on the subject 

 may be found in Kessel, Schlomka, Ferreri, Gray, Oetteking, and 

 other authors, but there is nothing to afford any definite aid in the 

 attempt at a classification of these growths. 



Marx (1926, p. 502) thus summarizes the results of the histological 

 studies of ear exostoses up to his time : 



They consist of compact bone without distinct medullary spaces, but often 

 with strikingly marked vascular canals. In substance the "exostosis eburnea " 

 and the " exostosis spongiosa " are not different, but it is to be accepted that 

 one form passes into the other (Weber, Virchow, Schwartze), and that occa- 

 sionally also mixed forms are encountered. 



Finally, Moller-Holst (1932, pp. 69, 100) states: 



Some exostoses consist only of cancellous bone and will therefore be desig- 

 nated as exostosis spongiosa, others are covered with a compact layer and are 

 called exostosis cburnca. Histological examinations by the clinicians have shown 

 that between the two extremes (the compact and -the spongy exostoses) occur 

 all transitions. 



Remarks. — The only conclusion that can be drawn from the his- 

 tological evidence regarding the bony growths in the ears is that they 

 all together constitute but one abnormal complex, which offers nu- 

 merous individual differences, grades, and variations. 



NATURE 



What, in the opinion of those who have dealt with the condition, 

 is the nature, pathologically, of ear exostoses? There are numerous 

 opinions on this subject, but in general they are based on limited in- 

 dividual observations, and that mostly clinical, which do not permit 

 of a sufficient perspective and grasp. However, it is interesting to 

 survey these opinions. 



Roosa (1866) concluded that ear exostoses " were morbid growths 

 consequent on local irritation." 



