196 



ANATOMY OF THE RABBIT 



chiefly for the accommodation of the lips, which in this region en- 

 croach medially on the oral cavity. The medial surface of the 

 horizontal portion forms an acute angle with that of the bone of 

 the opposite side, except anteriorly, where it bears a roughened 

 area for articulation with the latter. Running backward from the 

 symphysis there is a broad horizontal ridge, representing the 

 mylohyoid line (linea mylohyoidea), the line of attachment of the 

 mylohyoid muscle. The mandibular foramen, through which, in 

 the natural condition, the inferior alveolar nerve and artery gain 

 access to the interior of the bone, and through which the inferior 

 alveolar vein emerges, lies on this surface at the junction of the 

 horizontal portion with the ramus. The corresponding mental 

 foramen (foramen mentale), through which branches of these 

 structures leave the mandible, is situated on the lateral surface in 

 front of the first premolar. The mandibular foramen is closely 

 connected with a second aperture lying at the ventral end of the 

 sulcus ascendens, directly behind the last molar, and serving for 

 the transmission of an anastomotic vein connecting the inferior 



alveolar and the deep facial veins 

 (p. 298). 



The mandibular ramus forms, 

 in general, an obtuse angle with 

 the horizontal portion. As in other 

 herbivores, the ventral part, dis- 

 tinguished as the angle, is greatly 

 increased in size at the expense of 

 the condyloid process and to a still 

 greater extent of the coronoid pro- 

 cess, the latter being vestigial. In 

 addition to a low pterygoid tuber- 

 osity (tuberositas pterygoidea), 

 situated at the posterior projecting 

 point of the angle, the posterior 

 and ventral margins of the angle 

 are excavated on the medial side of 

 the bone, so that they form the 

 boundary of a pronounced, though 

 shallow, inferior pterygoid depres- 



s-m 



m ct 



Fig. 91. Lateral surface of the hyoid 

 and larynx: c.a., arytenoid cartilage; 

 c.c, cricoid cartilage; c.i., inferior cornu 

 of thyreoid cartilage; cm., lesser cornu 

 of hyoid; c.mj., greater cornu of hyoid; 

 C.S., superior cornu of thyreoid 'cartilage; 

 ct., left plate of the thyreoid cartilage; 

 e, epiglottic cartilage; f.t.s., thyreoid 

 foramen; l.h., lateral hyothyreoid liga- 

 ment; l.h.m., median hyothyreoid liga- 

 ment; m.ct., cricothyreoideus muscle; 

 o.h., hyoid bone; s.m., stylohyoideus 

 minor muscle; s.mj., stylohyoideus major 

 muscle; tr., cartilaginous tracheal rings. 



