The medial surface (Fig. 37) is smooth and has near its caudal end a foramen, the =mandibular foramen= (_f_), which communicates with the mandibular canal leading lengthwise through the bone to the mental foramen. The cranial end is roughened for attachment to the bone of the opposite side. The ventral border is smooth and rounded; it ends caudally in a blunt point, the =angular process= (_g_). The dorsal (alveolar) border is slightly curved and bears the sockets (=alveoli=) for the teeth. It is continuous with the cranial margin of the coronoid process. The ramus is divided into two portions, the =coronoid= process (_h_) and the =condyloid= process (_i_). The coronoid process (_h_) extends dorsocaudad as a thin plate of bone with smooth surfaces and borders. Its outer surface is partly occupied by the =coronoid fossa= (_e_). The condyloid process (_i_) has the form of a semicylindrical transverse piece of bone attached to the caudal margin of the coronoid process. It articulates with the mandibular fossa of the temporal bone. =Hyoid Bone.= =Os hyoideum= (Fig. 38 and Fig. 104).--The hyoid bone forms the support for the tongue and gives origin to muscles passing to the tongue and larynx. It also supports the thyroid cartilage (Fig. 104, 1). [Illustration: FIG. 38.--HYOID BONE, DORSAL VIEW. _a_, body; _b_, _c_, _d_, _e_, cranial cornu; _f_, caudal cornu; _b_, ceratohyal; _c_, epihyal; _d_, stylohyal; _e_, tympanohyal; _f_, thyrohyal.] It consists of a transverse bony bar, the =body= (Fig. 38, _a_) and of two =cornua= or horns attached to each end of the body. The cranial cornu (lesser cornu of human anatomy) is the longer (Fig. 38, _b_-_e_). Each arises from the cranial face of the body at its lateral end, curves laterad, and then caudodorsad. It consists of four bony pieces movably united by cartilage. The terminal piece is the =tympanohyal= (_e_); it is imbedded in the tympanic bulla just ventrad of the stylomastoid foramen. It is not therefore seen attached to the cornu after the latter has been separated from the skull. The other pieces become successively shorter toward the body, and are called =stylohyal= (_d_), =epihyal= (_c_), and =ceratohyal= (_b_). The caudal cornua (_f_) (greater cornua of human anatomy) arise from the ends of the body. Each consists of a single piece of bone, the =thyrohyal= (_f_), which passes caudolaterad; its free end is united to a process of the thyroid cartilage (Fig. 104, 1). =The Skull as a Whole.=--In the following description of the skull as a whole the mandible, hyoid, and ear-bones are not included. The skull forms a bony box which contains the brain and is produced craniad into the =facial= portion which encloses the nasal cavity and forms the framework of the face.