556 



ORGAN OF HEARING. 



auditory passage to the membrana tympani, 

 between the layers of which it glides and sepa- 

 rates into very delicate filaments, by one or two 

 of which it anastomoses with the chorda tym- 

 pani. The last branch of the superficial tem- 

 poral nerve sends filaments to the auricle and 

 its anterior and superior muscles. 



The third and most considerable branch of 

 the auricular nerve of the pneumogastric, 

 ramus auricu/aris nervi vagi, gets into the canu- 

 liculus mastoideus of Arnold, through an open- 

 ing near the lower aperture of the cunalis c/iordts 

 tympani. It heie divides into two branches, 

 one of which joins, as has been said, the pos- 

 terior auricular branch of the facial nerve; the 

 other, which is stronger, arrives at the posterior 

 wall of the external auditory passage, gives 

 filaments to the ceruminoiis glands, and in 

 company with a branch of the posterior auricu- 

 lar artery penetrates the cartilage of the ear to 

 ramify on the skin covering its convex surface. 

 Arteries of the external ear and tympanum. 

 The posterior auricular artery. This sup- 

 plies branches which ramify on the convex 

 surface of the auricle, and also turn over the 

 helix to spread out on the other surface. Twigs 

 are also given off to the auditory passage. 



A remarkable branch of the posterior auri- 

 cular is the slylo-miistoid artery. This enters 

 the stylo-mastoid hole and runs along the 

 aqueduct of Fallopius, and ends by anasto- 

 mosing with a branch of the middle meningeal, 

 called the Vidian artery, which enters by the 

 hiatus of Fallopius. In its course the stylo- 

 mastoid artery transmits twigs to the mastoid 

 cells, the external auditory passage, the mem- 

 brana tympani, the stapedius muscle, and the 

 external semicircular canal. 



The twig to the membrana tympani is called 

 arteria tympanica superior. This artery, toge- 

 ther with the arteria tympanica inferior from 

 the internal maxillary, supplies the membrana 

 tympani. The arteries run round the circum- 

 ference of the membrane and down along the 

 handle of the malleus, and branching out form 

 by their inosculations a fine net-work. 



The temporal artery sends branches to the 

 anterior part of the auricle, the external auditory 

 passage, and to the ceruminous glands. It also 

 gives off a branch which enters the tympanum 

 by the fissure of Glasser, and ramifies in the 

 mucous membrane of the outer wall of that 

 cavity. 



The occipital artery gives twigs to the auricle. 

 The internal maxillary artery. This artery 

 gives off a branch to the joint of the lower jaw, 

 a twig of whifh, the arteria tympanica inferior, 

 just mentioned, passes through the fissure of 

 Glasser into the tympanum and inosculates on 

 the membrana tympani with the twigs of the su- 

 perior tympanic artery of the stylo-mastoid. The 

 internal maxillary also sends a branch, the deep 

 auricular artery, arteria auricularis profunda, 

 to the cartilaginous portion of the auditory 

 passage, where it supplies the lining integu- 

 ment and glands. It moreover sometimes gives 

 small branches to the Eustachian tube. 



The middle meningeal artery in the first part 

 of its course gives branches to the Eustachian 



tube. In the cranium it sends a branch, arteria 

 Vidiana, into the Fallopian canal, which has 

 been already described as anastomosing with 

 the stylo-mastoid. It also sends branches to 

 the tympanum, which ramify in the mucous 

 membrane of that cavity and in the muscles of 

 the small bones. 



The accessory middle meningeal artery, when 

 present, gives branches to the Eustachian tube. 

 The inferior pharyngeal artery also gives 

 branches to the Eustachian tube, to the pyramid 

 and cavity of the tympanum. The Eustachian 

 tube also receives twigs from the inferior pala- 

 tine branch of the facial artery. 



The internal carotid, before entering the 

 cranium, sometimes gives a small twig to the 

 Eustachian tube and sends another, through a 

 small passage leading from the carotid canal 

 into the tympanum, to the promontory. 



In some animals, such as the mole, the 

 squirrel, the guinea-pig, the marmot, Sec. there 

 is an osseous canal like a bar of bone extending 

 over the vestibularfenestra and running through 

 between the crura of the stapes. This was 

 first observed by Sir Anthony Carlisle in the 

 marmot and guinea-pig, who describes it as 

 " an osseous bolt to rivet it (the stapes) to its 

 situation."* The canal is for the passage of an 

 artery and nerve which in some other animals 

 are unprovided with an osseous canal in their 

 course through the stapes. The artery running 

 through the stapes was observed about ten 

 years ago by Professor Ottof in hybernating 

 animals; but Professor Hyrtl of Prague} has 

 shewn that the artery is by no means peculiar 

 to those animals, as it does not occur in all, 

 and as it occurs in animals which do not hyber- 

 nate. 



Mr. Shrapnel 1 describes in the human ear 

 an artery accompanied by a nerve, passing 

 through the membrane which fills up the space 

 between the arms of the stapes. Mr. Shrapnell 

 was led to this observation from what he had 

 seen in the rat, viz. a nerve and artery passing 

 through the stapes and supported by a minute 

 channel of bone. Professor Hyrtl || has more 

 recently described three modes of distribution 

 of the arteries in man, which he has met with, 

 analogous to the artery running through the 

 stapes in the animals above mentioned. 



The arteries of the external and middle ear 

 are accompanied by corresponding veins. As 

 to lymphatics, there are some small glands 

 behind the auricle and in front of the mastoid 

 process. The lymphatic vessels of the external 

 ear accompany the arteries and veins, but prin- 

 cipally the latter. Little or nothing is known 

 of the lymphatics of the tympanum. 



* On the Physiology of the Stapes in Philosoph. 

 Trans. 1805, p. '204. 



t Nova Acta Acad. Caes. Leop., torn. xiii. 

 p. 662. 



, . . 

 p. 457, Wien 1836. 



On the Nerves of the Ear, in London Medical 

 Ga'zctte, vol. x. p. 507, 1832. 



|| I,,,.-, cit. 



