750 



THE EAR. 



end of the Eustacliian tube and the adjoining surface of the sphenoid bone, 

 and from the sides of the upper compartment of the Eustachian orifice. In 



Fig. 504. 



Fig. 504. VIEW OF THE CAVITY 

 OF THE EIGHT TYMPANUM FROM 

 ABOVE. 



The cavity of the tympanum 

 and some parts of the labyrinth 

 have been exposed by a horizontal 

 section removing the upper part of 

 the temporal bone. 1, posterior 

 semicircular canal opened ; 2, the 

 cavity of the cochlea opened ; 3, 

 osseous part of the Eustachian 

 tube ; 4, head of the malleus ; 5, 

 incus ; 6, stapes, with its base set 

 in the fenestra ovalis ; 7, tensor 

 tympani muscle ; 8, stapedius. 



this canal the muscle is con- 

 ducted nearly horizontally 

 backwards to the cavity of 

 the tympanum. Immediately 

 in front of the fenestra ovalis 

 the tendon of the muscle 

 bends at nearly a right angle 

 over the end of the processus 

 cochleariformis as through a 

 pulley, and, contained in a 

 fibrous sheath, passes out- 

 wards to be inserted into the 

 inner part of the handle of 

 the malleus, near its root. 



The laxator tympani (laxator tympani major of Sommerring) is generally 

 believed to be distinctly muscular, but being partly concealed by a band of 

 fibrous tissue, doubts are still entertained by some observers as to whether 

 the structure known under this name is of a muscular or ligamentous nature. 

 Arising from the spinous process of the sphenoid bone, and slightly from 

 the cartilaginous part of the Eustachiau tube, it is directed backwards, 

 passes through the Glaserian fissure, and is inserted into the neck of the 

 malleus, just above the root of the processus gracilis. 



The laxator tympani minor of Sommerring (posterior ligament of the malleus, Lincke) 

 is made up of reddish fibres, which are fixed at one end to the upper and back part of 

 the external auditory meatus, pass forwards and inwards between the middle and 

 inner layers of the membrana tympani, and are inserted into the outer border of the 

 handle of the malleus, and the short process near it. Sommerring. Icones Organi 

 Auditus Humani, 1801. 



The stapedius is a very distinct muscle, but is hid within the bone, being 

 lodged in the descending part of the aqueductus Fallopii and in the hollow 

 of the pyramid. The tendon issues from the aperture at the apex of that 

 little elevation, and passing forwards, surrounded by a fibrous sheath, is 

 inserted into the neck of the stapes posteriorly, close to the articulation of 

 that bone with the lenticular process of the incus. 



A very slender spine of bone has been found occasionally in the tendon of the 

 stapedius in man : and a similar piece of bone, though of a rounder shape, exists con- 



