THE HEAD AND NECK. 



109 



and direct them towards the internal, delicate, and 

 beautifully-constructed apparatus in which, by their 



oc. 



Fig. 16.— Side view of the skull of horse, with the 

 bone removed so as to show the ^hole of the 

 teeth, n, nasal "bone ; o, orbit ; z, zygomatic arch ; 

 t, temporal fossa ; oc, occipital condyle ; em, exter- 

 nal auditory opening ; g, glenoid fossa for articula- 

 tion of the lower jaw; »', i l , i % , the three incisor 

 teeth ; c, the canine ; pm 1 , the situation of the ru- 

 dimentary first premolar, which has been lost in 

 the lower, but is present in the upper jaw ; pm*, 

 pm z , and pm 4 , the three fully-developed premolar 

 teeth ; m\ m?, and m 3 , the three true molar teeth. 



effects upon the terminations of the auditory nerve, 

 they produce the sensation of hearing. 



In front of the ear-opening arises a curious bridge 

 of bone (z), which arches forwards to join the skull 



