NO. 6 EAR EXOSTOSES— HRDLICKA 49 



Alexander (1930) regards both hyperostoses and exostoses — sep- 

 arable only by their form — when slight as variations, when large as 

 tumors, 



Refimrks. — It must be clear from the above that the pathognomy 

 of ear exostoses is a subject that is as yet by no means as elucidated 

 as might be desired. The relative rarity of the condition in the living, 

 its clinical disadvantages, the want in many cases of the assistance of 

 an expert histo-pathologist, all constitute serious difficulties in this 

 field. Perhaps the extensive observations that form the basis of this 

 report may help to throw some light on the matter ; this will be dealt 

 with in the terminal discussion. 



ETIOLOGY 



The causation of ear exostoses, being of especial importance to 

 otology, has received considerable attention ; nevertheless, here also 

 much still remains obscure. The subject has naturally a direct con-, 

 nection with that of pathognomy of the growths. 



A general review of the observations and opinions recorded in this 

 part of the field shows that attention has been concentrated mainly 

 on the local or exciting agencies and on the possible connection of 

 the exostoses with certain systemic conditions or diseases. Never- 

 theless, there are also a number of valuable observations on the heredity 

 of the growths. It will be well to take up separately the various etio- 

 logical factors involved. 



TRUE CAUSES " UNKNOWN " 



A large majority of the authors who deal more adequately with 

 the etiology of ear exostoses acknowledge more or less openly that 

 the true or basic causes of this class of disorders are unknown or 

 uncertain. 



Statements such as " nothing positive ", " still dark as to the causes ", 

 " true causes unknown ", and others of similar import may be found 

 in Turner, Blake, Garrigou-Desarenes, Ferreri, Lake, and many 

 others. Hedinger (1881), "pathogenesis entirely unknown"; Whit- 

 ney (1886, p. 41), "various explanations have been offered for the 

 occurrence of the growth in this situation, but none of these is entirely 

 satisfactory " ; Kessel (1889), " causes still but little known " ; Gold- 

 stein ( 1898), " etiology often shrouded in mystery "; Politzer (1902, 

 p. 210), " the causes of these exostoses are, in the majority of cases, 

 not ascertainable." Le Double and Lebourg ( 1903 ) , " causation uncer- 

 tain " ; Bachauer (1909), "cause not yet found"; Burton (1927). 



