EXTERNAL AUDITORY CANAL. 



79 



glands ; and in the thick subdermic tissue are small oval convoluted tubular glands 

 of a brownish-yellow colour, agreeing in form and structure with the sweat glands, 

 but larger in part or entirely, and in sufficient number at some parts, especially 

 where cartilage is deficient, to form an almost complete layer in the subcutaneous 

 tissue. The cerumen or ear-wax is secreted by these glands (glandulm ceruminosce), 

 and their fine ducts may be seen to perforate the skin of the meatus close to or 

 into the mouths of the hair follicles. According to Schwalbe the fatty part of the 

 ear-wax is formed by the sebaceous glands. This may be partly the case, but the 

 secretion of the ceruminous glands is certainly also of a fatty nature (fig. 88). 



Vessels and nerves. The external auditory meatus is supplied with arteries 

 from the posterior auricular, internal maxillary, and temporal arteries. The principal 



Fig. 88. SECTION OP SKIN OP 



AUDITORY MEATUS, INCLUDING 

 TWO CERUMINOUS GLANDS. 



(Griiber.) 



root of hair -i 



'V 

 I ; 



hair 



sebaceous 

 yland 



& Wide 



branches of the arteries 

 course along the upper and 

 back wall of the canal. The 

 veins and lymphatics take 

 the same course on leaving 

 the meatus as do the corre- 

 sponding vessels of the 

 pinna. The nerves are 

 derived from the auriculo- root-sheath -ffi 

 temporal branch of the fifth 

 and the auricular branch of , /* 3$ 

 the vagus. The latter sup- 

 plies the skin of the osseous 

 part of the canal and that 

 which covers the lower part 

 of the tympanic membrane. 

 State in the infant. 

 The auditory passage is 

 only in part formed of bone 

 and cartilage in the infant. 

 The osseous part is formed 

 at birth by a small ring 

 of bone (tympanic bone) 

 which is deficient antero- 

 superiorly, where it is completed by uniting with the squamous portion of the 

 temporal bone, and this part of the temporal overhangs the meatus and con- 

 stitutes the chief part of its superior boundary. The floor is mainly formed by 

 fibrous tissue which unites the tympanic ring of bone with the fibro-cartilage 

 of the pinna and external part of the meatus. This is the fibrous tympanic 

 plate of Symington, and into it the tympanic bone gradually grows after birth. 

 This growth takes place chiefly from two points (Zuckerkandl) outwards into 

 the fibrous plate in question and usually in such a manner that a gap is left for 

 some time in the antero-inferior part of the bony meatus which sometimes persists 

 throughout life. The membrane of the drum is more inclined away from the 

 vertical in the foetus and new-born infant than in the adult, being in fact in the 

 same plane as the roof and overlying the fibrous floor of the inner part of the 



cerumiiunts 

 glands 



