THE STRUCTURE OF THE HUMAN SKILL, 125 



the posterolateral apertures of the cranium may be said to 

 be stopped by the osseous chambers of the auditory organ, 

 in the same way as the anterior apertures are closed by the 

 osseous chambers of the olfactory organs. As the eye is con- 

 tained only in a mobile fibrous capsule, the sclerotic, the 

 apertures which lead to the orbit — the spheno-orbital fissures 

 and the optic foramina — are not closed by any special bones 

 pertaining to the sensory organ lodged therein. 



Thus the brain-case may be said to be composed of three 

 superior arches connected respectively with the three divisions 

 of the basi-cranial axis, and of two pair — an anterior and a 

 posterior — of bony sense capsules interposed between these 

 arches. A middle, third pair of sense capsules is not repre- 

 sented by bone in the cranial walls. 



In like manner, the face may be resolved into a series of 

 bones, occurring in pairs from before backwards, and forming 

 more or less well-defined lower arches, some of which embrace 

 the nasal cavity, being placed in front of, or above, the oral 

 aperture, while others enclose the buccal chamber, and are 

 situated behind and below the oral aperture. Of the former, 

 fre-oral bones, there are four pairs — the Premaxillte (Pmx.), 

 the MaxiUm (Mx.), the Palatines (PI), and the Pterygoids (Pt.). 



The Premaxillw, which lodge the upper incisor teeth, so 

 early lose their distinctness in man, by becoming anchylosed 

 with the maxillary bones (at any rate externally and anteriorly) 

 that they are rarely recognised as separate bones. Neverthe- 

 less, a suture extending upon the bony palate from the pos- 

 terior margin of the alveolus of the outer incisors to the 

 incisive foramen, very commonly persists, as an indication of 

 the primitive separation of these bones. The most important 

 character of the premaxilla?, regarded morphologically, is, that 

 they are connected, superiorily, with the anterior termination of 

 the cranio-facial axis, and that this connection is a primary one. 

 Each premaxilla passes from its inner end, which is united with 

 the axis, outwards and backwards, and two of the other three 

 pair of pre-oral bones have similar relations to the cranio-facial 

 axis. The anterior of these are the Palatine bones ; the inner, 

 or sphenoidal, processes of which are connected with the basi- 



