Chap, v.] THE EAR. 59 



the punctum falls away from the globe, and, moreover, 

 the passage of the tears is no longer aided by the 

 suction action effected by the muscle in the process of 

 winking. The canaliculi may readily be slit up by 

 a proper knife, and a probe can without difficulty be 

 passed down the nasal duct from the lachrymal sac. 

 The duct is a little over half an inch in length, and 

 the probe that traverses it should pass downwards, 

 and a little backwards and outwards. 



As affections of the lachrymal sac are often very 

 painful, it may be noted that the nerve supply of the 

 sac is derived from the infratrochlear branch of the 

 nasal nerve. 



CHAPTER V. 



THE EAR. 



THE pinna and external auditory meatus. 



The pinna may be congenitally absent, or may be 

 supplemented by supernumerary portions of the 

 auricle, which may be situated upon the cheek or 

 side of the neck. In the latter situation they are 

 sometimes found at the hinder part of a " branchial 

 fistula." (See page 146.) The pinna may present a con- 

 genital fistula, which is due to defective closure of the 

 first visceral cleft. This cleft is represented in the 

 normal ear by the Eustachian tube, the tympanum, 

 and the external auditory meatus, the pinna being 

 developed from the integument behind the cleft. 

 In these congenital fistulse, when well marked, - 

 the pinna is cleft just in front of the tragus, or 

 through the helix, and there is more or less failure in 

 the closing of the meatus and tympanum, while the 

 membrana tympani will be more or less deficient, or 



