Chap.v.j THE EAR. 65 



This nerve is a branch of the third division of the 

 fifth, and it is from this same division that the branches 

 come off that supply the muscles of the jaw. 



The inferior dental nerve, that goes to the lower 

 teeth, is a branch of the same division, as is. also the 

 gustatory nerve ; and the somewhat direct connection 

 of these nerves with the ear may explain the frequent 

 association of ear-ache and tooth-ache, and the fact 

 that disease in the anterior part of the tongue 

 (gustatory nerve) is often attended by pain in the 

 ear. 



It is a common practice to introduce ear-rings, 

 with the idea of relieving obstinate affections of the 

 eye. How such a treatment can act, if it acts at 

 all, is hard to understand. It is true that the main 

 nerve-supply of the eye and of the conjunctiva comes 

 from the fifth nerve, but, unfortunately for any nerve 

 theory, the lobule of the ear is only supplied by the 

 great auricular nerve. If the ear-ring, in such cases, 

 were introduced through the upper part of the ear, 

 supplied as it is in front by the fifth nerve, some 

 connection might be traced. 



Hilton reports a case of obscure pain in the ear 

 which was found to be due to an enlarged gland in the 

 neck, that pressed upon the trunk of the great auri- 

 cular nerve. 



Membrana tympani. This membrane is very 

 obliquely placed, forming with the horizon an angle 

 of 45. At birth it is much more nearly horizontal, 

 the angle being one of only 10. In cretins, and in 

 some idiots, it is said to retain this inclination through 

 life. Owing to the sloping downwards of the bony 

 wall of the meatus at its inner end, that wall forms 

 with the lower edge of the membrana a kind of sinus 

 in which small foreign bodies may readily lodge (Fig. 

 12). The ring of bone to which the membrane is 

 attached is deficient at its upper and anterior part. 

 F 



