Chap, v.) THE EAR. 69 



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 the so-called 

 supernumerary auricle consists in an irregular leaf of 

 fibro-cartilage developed from the margins of one of 

 the lower branchial clefts. (See page 168.) The tag- 

 like supernumerary auricles that are fcmnd on the 

 cheek just in front of the pinna or meatus, are due 

 to the irregular development or want of fusion of one 

 or more of the six tubercles from which the pinna 

 itself is developed. The pinna may present a con- 

 genital fistula. This may be due to a defective 

 closure of the first branchial 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 



