NO. 6 EAR EXOSTOSES HRDLICKA 4I 



entirely symmetric, both as to form and location." Noquet (1899) in 

 one case saw perfect symmetry on the two sides — the same aspect, 

 volume, point of origin ; Urbantschitsch had one case with two ex- 

 ostoses in each meatus, exactly alike. Sabroux alone (1901, p. 35) 

 considers them as " very rarely implanted symmetrically in the two 

 auditory canals." For Korner (1904, p. 107) they "develop mostly 

 symmetrically"; and also for Moller-Holst (1932, p. 96), "they in 

 part develop very symmetrically." 



NcTV observations. — No statistical data have been attempted in this 

 connection, for it was learned that a tendency toward symmetry, where 

 both external auditory canals are affected by exostoses, is the general 

 rule. The likeness extends most to the location of the growths, less to 

 their number and size, and least to the details of their shape. Even 

 where the growths must be recorded as unilateral, there is frequently 

 a trace of a commencing tumefaction in the corresponding locality of 

 the other meatus. 



This general tendency of the growths toward symmetry on the two 

 sides connects them clearly, in the view of the writer, with the central 

 neuro-vascular system and is another element of importance in the 

 etiology of these formations. 



RATE OF GROWTH 



An inquiry into this subject is possible only to the clinician. There 

 are a number of notes on the subject in otological literature. 



Toynbee (i860) learned that the development of these tumors may 

 frequently be very gradual and " unattended by any symptoms calcu- 

 lated to attract the attention of the patient." Dalby (1876) found 

 that ear exostoses " may remain without perceptible change for many 

 years." 



In the observation of Von Troeltsch (1881), their growth was gen- 

 erally very slow; Braunberger (1896) stated that it was "slow and 

 painless." Kessel (1889, p. 288) noted that, although usually slow, 

 their growth at times was rather rapid. " It was most accelerated 

 toward the time of puberty; older age retards growth. The growth 

 is sometimes uneven ; it can cease for a time and then recommence." 

 In Stewart's (1901) experience, although such an occurrence was 

 " extremely rare ", yet on occasion these exostoses could take on a 

 rapid growth suddenly. 



A summary of all the clinical observations on the rate of growth 

 of ear exostoses is that their early stages are slow, symptomless, and 

 usually ignored even by the subject ; that many a]>parently stop all 

 growth after reaching a smaller or larger size ; but that under exciting 



