

THE BONES. 47 



46. I. THE HEAD, caput. 



The twenty-two bones of the head may be divided into two 

 classes ; the bones of the cranium, of the skull, ossa cranii, 7, 

 and the bones of the face, ossafaciei, 15. 



A. Bones of the skull, ossa cranii. 

 a. The Azygos bones, in the central line. 

 Os basilare, the foundation bone, consists of: 



47. 1. Os occipitalis, i\\e occipital bone. 



Position : at the posterior, inferior part of the head, immediately 

 above the vertebral column. 



Figure : a shallow shell placed vertically, with a horizontal 

 portion, united by a ring. 



Portions: pars occipitalis ; 2 partt. condyloidese; p. basilaris. 



Between which, for. occ. magnum. 



Junctions : with six bones : two parietal, above ; two temporal, 

 laterally and below ; one sphenoid, before ; and Atlas, beneath. 



a. Pars occipitalis, the upright shell ; below, passing into the condyloid por- 

 tions, is itself limited by the foramen magnum, and united above to the parietal 

 bones, sut. lambdoidalis, below, to the mastoid portions of the temporal bones, 

 additamentum sut. lamb. 



1. The external or posterior surface; convex, presents, extending from the 

 foramen magnum upwards, the crista and spina occipitalis externa (for the lig. 

 NuchcK); laterally, from the crest, the linea semicircularis inferior (for the muse, 

 rectus capitis post, maj., obliquus sup.'), and superior (for the m. occipital, et tra- 

 pezius). 



2. The internal, anterior surface; concave; divided into four fossae, two 

 superior, fossce cerebri; two inferior, fosste cerebelli. In the centre, the protube- 

 rantia (spina), interna seu cruciata (for torcula Herophili) ; perpendicular; crista 

 interna (for falx cerebelli) to the foramen magnum; horizontal: linea transversce 

 (for tentorium cerebelli), with the sulcus transversus (for the sinus transversus^. 

 Above the protuberance ascends the sulcus longitudinalis superior, generally on 

 the right side. 



b. Partes condyloidece, articular portions ; on either side of the for. magnum 

 anteriorly. 



1. Inferior surface; convex, elliptical, smooth; rests upon the processus obliq. 

 super, of the Jltlas. Behind, the condylus. fossa condyloidea post., frequently 

 perforated by the for. poster, for an emissar. Santorini; laterally ; fossa cond. ant. 

 with the foram. cond. ant., (for the lingual or hypoglossal nerve) ; externally ; 

 the processus, (for the rect. capt. later alls muse.), and indsura jugularis, which 

 forms with the petrous bone the for. jugulare, the opening for the commence- 

 ment of the jugular vein. 



2. Superior, cerebral surface; concave; exhibits the processus anonymus; 

 foram. condyl. ant. et post., their internal openings; and a part of the sulcus 

 transversus. 



c. Pars basilaris, base or cuneiform process; azygos, in the centre before the 

 for. magnum, behind the sphenoid bone and united with these. 



