128 SPECIAL ANATOMY OF THE SKELETON 



is the internal auditory meatus, for the facial and auditory nerves and auditory 

 artery; behind and external to this is the slit-like opening leading into the aquae- 

 ductus vestibuli, which lodges the ductus endolymphaticus; while between the two 

 latter, and near the superior border of the petrous portion, is a small, triangular 

 depression, the remains of the floccular fossa, which lodges a process of the dura 

 and occasionally transmits a small vein from the substance of the bone. Behind 

 the foramen magnum are the quadrilateral inferior occipital fossae, which lodge 

 the hemispheres of the cerebellum, separated from each other by the internal 

 occipital crest, which serves for the attachment of the falx cerebelli and lodges the 

 occipital sinus. The posterior fossae are limited above by the deep transverse 

 grooves for the lodgement of the lateral sinuses, which diverge forward on each 

 side from a depression in the mesal plane, the torcular. These channels, in their 

 passage outward, groove the occipital bone, the posterior inferior angles of the 

 parietals, the mastoid portions of the temporals, and the jugular processes ol 

 the occipital, and terminate at the back part of the jugular foramen. Where the 

 lateral sinus grooves the mastoid portion of the temporal bone the orifice oi 

 the mastoid foramen may be seen. Just previous to the termination of the groove 

 the posterior condylar foramen opens into it. Neither foramen is constant. 



The basilar surface (norma basalis) (Fig. 97) of the skull is extremely irregular. 

 It is bounded in front by the incisor teeth in the maxillae; behind by the superior 

 curved lines of the occipital bone; and laterally by the alveolar arch, the lower 

 border of the malar bones, the zygoma, and an imaginary line extending from 

 the zygoma to the mastoid process and extremity of the superior curved line 

 of the; occiput. It is formed by the palatal processes of the maxillae and palate 

 bones, the vomer, the pterygoid processes, under surface of the greater wings, 

 spinous processes and part of the body of the sphenoid, the under surface of the 

 squamous, mastoid, and petrous portions of the temporals, and the under surface oi 

 the occipital bone. The anterior part of the base of the skuU is raised above the 

 level of the rest of this surface (when the skull is turned over for the purpose oi 

 examination), is surrounded by the alveolar process, w r hich is thicker behind than 

 in front, and excavated by sixteen depressions for the lodgement of the teeth oi 

 the maxillae, the cavities varying in depth and size according to the teeth they con- 

 tain. Immediately behind the incisor teeth is the anterior palatine fossa. At the 

 bottom of this fossa may usually be seen four apertures, two placed laterally, the 

 foramina of Stenson, which open above, one in the floor of each nostril, and trans- 

 mit the anterior branch of the posterior palatine vessels, and two in the median 

 line in the intermaxillary suture, the foramina of Scarpa, one in front of the other, 

 the anterior transmitting the left, and the posterior (the larger) the right, naso- 

 palatine nerve. These two lateral canals are sometimes wanting, or they may 

 join to form a single one, or one of them may open into one of the lateral canals 

 above referred to. The palatine vault is concave, uneven, perforated by numerous 

 foramina, marked by depressions for the palatine glands, and crossed by a crucial 

 suture, formed by the junction of the four bones of which it is composed. At the 

 front part of this surface a delicate linear suture may frequently be seen, passing 

 outward and forward from the anterior palatine fossa to the interval between the 

 lateral incisor and canine teeth, and marking off the premaxillary portion of the 

 bone. At each posterior angle of the hard palate is the posterior palatine foramen, 

 for the transmission of the posterior palatine vessels and great descending palatine 

 nerve; and running forward and inward from it a groove, for the same vessels and 

 nerve. Behind the posterior palatine foramen is the tuberosity of the palate bone, 

 perforated by one or more accessory posterior palatine canals, and marked by the 

 commencement of a ridge which runs transversely inward, and serves for the 

 attachment of the tendinous expansion of the Tensor palati muscle. Projecting 

 backward from the centre of the posterior border of the hard palate is the posterior 



