300 



AN INTRODUCTION TO ZOOLOGY 



the mandible is inserted. On the inner side of the ramus just below 

 and in front of the condyle lies the inferior dental foramen, which 

 allows the inferior dental nerve, a branch of the trigeminal, and the 

 similarly named artery that accompanies it to enter the substance 

 of the bone. A terminal branch of the same nerve leaves the outer 

 surface of the jaw by the mental foramen, just behind and below 



B 



FIG. 101. -Hyoid bone of 

 Canis. 



B., body of hyoid, basi-hyal ; C., cera- 

 to -hyal ; E., epi-hyal ; S., stylo-hyal ; 

 C + E + S= anterior ; T M thyro-hyal, pos- 

 terior cornu. 



FIG. 102. Longitudinal section of a 

 molar tooth. From Owen. 



k., crown ; n., neck ; /., fangs ; e., enamel ; 

 d., dentine ; c., cement ; p., pulp cavity. 



the canine tooth, and is distributed to the lip and surrounding 

 tissues. 



The hyoidean apparatus is composed of a median portion, 

 the basi-hyal, and a pair of anterior and a pair of posterior cornua. 

 The basi-hyal, or body of the hyoid, is a small transverse flattened 

 bar of cartilage bone somewhat thickened and turned up at its 

 ends. The posterior cornua are short rods of bone articulating with 

 the outer extremities of the basi-hyal. They pass upwards and 

 are attached to the thyroid cartilage of the larynx and hence are 

 termed the thyro-hyals. The anterior cornua are longer rods 

 passing in a curved manner upwards and outwards and forming 

 a connection with the cranium in the region of the tympanic bone. 

 This ossifies in four parts ; the most dorsal is the tympano-hyal, a 



