86 



APPLIED ANATOMY. 



of it is cartilaginous and a little over one-half bony. Viewed anteroposteriorly the 

 canal has a slight curve with its convexity upward (Fig. 100). Viewed from above 

 (Fig. 101 ), it is seen first to pass backward and then forward, forming an angle before 

 the bony wall is reached. In order to look into the ear and see the membrane it is 

 necessary to straighten the canal, either by inserting a speculum or by pulling the 

 auricle outward, upward, and backward. In children, upward traction is not so 

 necessary as in the adult. The length of the canal is approximately the same in child- 

 hood as in adults, but the bony part is still in a cartilaginous condition. The external 

 opening is oval, while farther in the canal is more circular; hence the Gruber speculum, 

 which is oval in shape, or the round speculum of Wilde can be used with almost 

 equal satisfaction. The point of junction of the bony and cartilaginous parts is 

 narrower than either end, and it is difficult to remove a foreign body which has 

 passed this point. This is particularly true in children, the lumen of the external 

 meatus being quite small and narrow while the tympanic membrane is nearly as 

 large as in adults. 



The floor is longer than the roof, owing to the drum membrane inclining at an 

 angle of 140 degrees. Cartilage forms the lower part of the canal, while the upper 



Carotid canal Eustachian tube 



Glenoid cavity 



Internal auditory meatu 



Membrana tyi 

 F 



Ceruminous glands 



FIG. ioi. Right ear; horizontal transverse section. 



part is completed by a fibrous membrane. Below and in front is the temporomaxillary 

 joint, and just posterior is the glcnoid lobe of the parotid gland. When the gland is 

 inflamed and swollen it presses on the -cartilaginous canal and produces pain; and 

 in cases of suppuration pus may discharge through the external meatus, gaining 

 access to the canal through fissures in the cartilage called the fissures of Santorini. 

 The cartilaginous portion of the meatus contains sweat-glands, sebaceous glands, and 

 hair-follicles. There are only a few glands in the upper posterior portion of the bony 

 meatus. On account of the location of the glands in the external portion of the canal, 

 accumulations of wax, and abscesses, which result from infection of the glands, occur 

 nearer to the surface than to the drum membrane. It is only when the canal begins to 

 fill up that the wax pushes its way to the membrane. When furuncles occur, the lining 

 membrane swells and by closing the canal prevents a view of the drum being ob- 

 tained. Incising of furuncles of the auditory meatus is sometimes required. The 

 site of the inflamed spot having been located, an incision can be made where 

 indicated. If care is exercised, one is not likely to injure the drum membrane, 

 because the abscess starts in one of the sebaceous glands, which are located in the 

 external half of the meatus. The membrane lies 2. 5 cm. from the surface, and the 

 point of the knife sho%ld not be carried so deeply as that for fear of wounding it; 

 there is no necessity of going so far inward. 



