72 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93 



of deformed skulls ( fronto-occipital, circular, and simple occi]:)ital ) . 

 and their aural exostoses. The results came out thus : 



Frequency of Ear Exostoses in Undeformed and Deformed Skidls of the Same People, 

 and in the Three Varieties of Deformed 



" Most, if not all, of these Peruvian skulls are really cases of artificial "flat-head" deformation, 

 but the pressure on the forehead was not sufficient to cause a permanent well-marked flattening of 

 the frontal bone. 



In this table, it will be noted, it is possible to compare directly the 

 percentages of specimens with exostoses in each category of the unde- 

 formed and deformed skulls, within the same ethnic series. The re- 

 sults are convincing. In every instance where both undeformed and 

 " flat-head " skulls existed in some quantities, the proportion of ear 

 exostoses is distinctly higher in the flat-heads. The fronto-occipital 

 deformation, therefore, it may now for the first time be said posi- 

 tively, favors somewhat the development of the growths. 



The simple occipital or cradleboard flattening has evidently but 

 small if any influence on the exostoses ; and the circular or Aymara 

 artificial deformation seemingly shows more of a checking than a 

 stimulating efl^ect on the growths. 



Just how the flat-head deformation may favor or excite the develop- 

 ment of ear exostoses is not clear. Many of these cases of deforma- 

 tion are not of extreme grades, and the skulls that are most deformed 

 do not by any means always show the abnormal ear growths ; the 

 occiu'rence of the latter, in other words, is not directly proportionate 

 to the grade of the distortion. 



Where the occiput has been much flattened in these cases — pressed 

 forward — a considerable stress has undoubtedly been transmitted to 

 the parts composing the external bony ear. But much the same com- 



