NO. 6 EAR EXOSTOSES HRDLICKA 9 



seacoast of Germany he encountered iii cases in 2,876 aural patients, 

 or 3.86 percent. 



One of the later treatises of anthropological interest on the auditory 

 canal and its exostoses is a dissertation by Bachauer (1909). He made 

 glue casts and measurements of the canal. Among the 33 Peruvian 

 skulls of the Munich anthropological collection (including doubtless 

 those reported upon by Ranke), he found 4 (12.1 percent) with 

 exostoses. Bachauer takes up various questions in connection with 

 the meatus. He finds that the only relation between the skull and 

 the auditory canal is that in general large skulls have large canals, 

 and small skulls smaller ones. He does not find that the dolicho- 

 cephalic have a round, and the brachycephalic an oval, meatus, as was 

 claimed by Ostmann. He also reaches the conclusion that race makes 

 no difference in the shape of the lumen of the canal. But there is a 

 decrease of the lumen in some deformed skulls. His wax casts com- 

 prised a series of deformed American and undeformed European 

 skulls. He measured the longitudinal and transverse diameters at the 

 orifice and found decreased lumen in 5 among 32 skulls from Pachac- 

 amac (15.6 percent). In three deformed skulls from that locality 

 there were slitlike canals. Bachauer's main deduction is that the cause 

 of the tympanic exostoses has not yet been found, but that their 

 formation is no special characteristic of the old Peruvians. 



In 1913, in my report on the results of my observations on the 

 skeletal remains in Peru, I gave the following brief note on ear exos- 

 toses (Hrdlicka, 1914) : 



A relatively large proportion of the pre-Columbian people of the more central 

 parts of the Peruvian coast suffered, as shown by the skulls, from a greater or 

 lesser occlusion of the external auditory canals by bony tumors. These are gen- 

 erally hard osteomata, from one to three in number, ranging in size from those 

 like a minute drop to those of several millimeters in diameter, mostly rounded 

 or pearl-shape, but occasionally irregular, frequently with enamel-like surface, 

 and situated just within, or perhaps protruding slightly from the orifice of the 

 osseous meatus. These little tumors, which are associated with no signs of 

 any inflammatory nature, develop invariably from the tympanic ring and particu- 

 larly from its extremities. They were in no case seen to coalesce, and though 

 they may almost close the meatus they were never seen to do this entirely. 

 Similar osteomata occur, though far less frequently, among the Whites ; and 

 they are found occasionally in the skull of a North American Indian. 



Further attention to aural exostoses, in part from the anthropo- 

 logical standpoint, is given by Burton (1927), who has studied 

 those parts of my Peruvian collections which are housed in the Mu- 

 seum of San Diego. Burton's examination of 26 deformed skulls 

 from Peru showed 5 cases of exostosis in the canal and i in the middle 



