450 ORGAN OF HEARING. 



below. Obstruction from inflammation and suppuration of this duct 

 constitutes .the disease called fistula lachrymalis. 



Vessels and nerves; The lachrymal gland is supplied with blood 

 by the lachrymal branch of the ophthalmic artery, and with nerves 

 by the, lachrymal branch of the ophthalmic and orbital branch of 

 the superior maxillary. 



THE ORGAN OF HEARING. 



The Ear is composed of three parts. 1. External ear. 2. Mid- 

 dle ear, or tympanum. 3. Internal e>ar, or labyrinth. 



The EXTERNAL EAR consists of two portions, the pinna and 

 meatus; the former representing a kind of funnel which collects the 

 vibrations of the atmosphere, called sounds, and the latter a tube 

 which conveys the vibrations to the tympanum. 



The Pinna presents a number of folds and hollows upon its sur- 

 face, which have different names assigned to them. Thus the ex- 

 ternal folded margin is called the helix (s\%, a fold). The eleva- 

 tion parallel to and in front of the helix is called antihelix (av<n, op- 

 posite.) The pointed process, projecting like a valve over the open- 

 ing of the ear from the face, is called the tragus (<rp<xyo, a goat), 

 probably from being sometimes covered with bristly hair like that 

 of a goat ; and a tubercle opposite to this is the anlitragus. The 

 lower dependent and fleshy portion of the pinna is the lobulus. The 

 space between the helix and antihelix is named the fossa innominata. 

 Another depression is observed at the upper extremity of the anti- 

 helix, which bifurcates and leaves a triangular space between its 

 branches called the scaphoid fossa ; and the large central space to 

 which all the channels converge is the concha, which opens directly 

 into the meatus. 



The pinna is composed of integument, fibro-cartilage, ligaments, 

 and muscles. 



The Integument is thin, and closely connected with the fibro-car- 

 lage. 



The Fibro-cartilage gives form to the pinna, and is folded so as 

 to produce the various convexities and grooves which have been 

 described upon its surface. The helix commences in the concha, 

 and partially divides that cavity into two parts ; on its anterior bor- 

 der is a tubercle for the attachment of the attrahens aurem muscle, 

 and a little above this a small vertical fissure, the fissure of the 

 helix. The termination of the helix and antihelix forms a length- 

 ened process, the processus caudatus, which is separated from the 

 concha by an extensive fissure. Upon the anterior surface of the 

 tragus is another fissure, the fissure of the tragus, and in the lobulus 

 the fibro-cartilage is wholly deficient. The fibro-cartilage of the 

 meatus, at the upper and anterior part of the cylinder, is divided 

 from the concha by a fissure which is closed, in the entire ear by 

 ligamentous fibres; it is firmly attached at its termination to the 

 processus auditorius. 



