THE HEAD AND NECK. 



109 



and direct them towards the internal, delicate, and 

 beautifully-constructed apparatus in which, by their 



oc. 



pm* 



FIG. 16. Side view of the skull of horse, with the 

 bone removed so as to show the whole of the 

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

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

 nal auditory opening ; g, glenoid fossa for articula- 

 tion of the lower jaw; ', P, * 3 , 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 9 , 

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

 teeth ; m 1 , 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 (2), which arches forwards to join the skull 



