A CLINICAL STUDY OF THE SKULL. 17 



the tips of the sphenoidal tongues can be substituted for it. The 

 production of this line across the norma will traverse on either side 

 the alisphenoid, at the region of the oval foramen, the articular 

 eminence, and the root of the zygoma. 



The transvei'se line can be intersected at its centre by a hypo- 

 thetical longitudinal line, which, passing through the mid-poin*^ of 

 the basion, can be produced so as to divide the norma into a right 

 and a left part. 



The points of the greatest interest in the region are the asymmetry 

 of the sides of the superior dental arch, the relative positions of the 

 oval foramina of the sphenoid bones, the position of the anterior 

 border of the articular eminence in connection with the trans- 

 verse line, the depth of the zygomatic fossa, the thickness of the 

 malar bone, the size of the bulbo petrosus — /. e., the rounded swell- 

 ing of the free part of the petrosa — and the angles formed by the 

 axes of the tympanic bones and the petrosa with the longitudinal 

 line. 



The left side of the dental arch has been found more frequently 

 expanded (it embracing a larger curve at the position of the first 

 and second molars) than is the right. With this expansion is 

 associated a diminished depth of the zygomatic fossa, a weaker ar- 

 ticular eminence, and a thinning of the zygomatic arch, as com- 

 pared with the same parts on the right side. The temporal ridge is 

 also the weaker on the expanded side. The significance of the 

 above facts appears to be as follows : The side of least expansion of 

 the dental arch is the stronger side ; hence a dental armature which 

 IS straight, or nearly so, is stronger than one which is curved. 



The base of the alisphenoid on the stronger side inclines to be 

 carried back farther than is the case on the weaker ; but this is 

 variable. 



The angles formed by the axis of the tympanic and the petrosal 

 elements vary on the two sides, but appear to be independent of the 

 changes in the anterior segment and the squamoso-malar series. 

 The asymmetry in the sides of the foramen magnum, and in the 



