548 



ORGAN OF HEARING. 



The long process of the malleus is directed 

 forwards, and lies in a groove within the anterior 

 part of that for the reception of the membrana 

 tympani, and close to the fissure of Glasser. 



To the top of the head of the malleus, a 

 ligament extends downwards from the upper 

 wall of the cavity of the tympanum. Another 

 ligament, known also under the name of the 

 great external muscle of the malleus, proceeds 

 from the spinous process of the sphenoid bone 

 backwards and inwards, through the fissure of 

 Glasser, and is inserted into the long process of 

 the malleus. A third ligament has been de- 

 scribed, as arising from within the upper and 

 posterior margin of the inner orifice of the 

 auditory passage above the margin of the mem- 

 brana tympani, and proceeding downwards and 

 inwards to be inserted into the handle of the 

 malleus below the short process, close to the 

 place where the connexion between the handle 

 of the malleus and the membrana tympani 

 ceases. Of this ligament, which has also been 

 described as a muscle, small external muscle of 

 the malleus, there is not much trace, except in 

 the reddish cellular tissue already mentioned. 



The body of the incus lies in the upper and 

 posterior part of the tympanic cavity. Its 

 articular surface, corresponding to that of the 

 malleus, is directed forwards, and a little up- 

 wards and outwards. The articulating surfaces 

 of the two bones are incrusted with cartilage, 

 and the joint is provided with a synovial mem- 

 brane, which is strengthened by ligamentous 

 fibres. The short branch is directed horizon- 

 tally backwards towards the entrance into the 

 mastoid cells, and is there fixed by means of a 

 short and broad ligament, which arises from a 

 small pit in the outer wall, and embracing its 

 extremity, is inserted on it. The long branch 

 extends perpendicularly downwards, almost pa- 

 rallel with the handle of the malleus, but nearer 

 the inner wall of the tympanum, towards which 

 its extremity, bearing the lenticular process, is 

 curved. 



The stapes, situated lower down in the cavity 

 of the tympanum than the other bones, lies 

 with its base applied to the vestibular fenestra, 

 to the circumference of which it is closely fixed 

 by a circular ligament, ligamentum annulare 

 baseos stapidis. This ligament springs from the 

 margin of the vestibular fenestra, and is inserted 

 into the jutting margin of the base of the stapes 

 all round. Besides this ligament, there are re- 

 flections of the membrane lining the tympanum, 

 and of that lining the vestibule. The con- 

 nexions of the base of the stapes with the ves- 

 tibular fenestra are such as to admit of some 

 degree of movement, but not to any very great 

 extent, so little, that it would seem one object 

 of the mechanism of the fenestra ovalis, and its 

 closure by the base of the stapes, was merely 

 to interrupt the continuity of the osseous walls 

 of the vestibule. 



The short branch .of the stapes is in front ; 

 the long branch behind, and its head outwards, 

 where it meets and articulates with the lenticu- 

 lar process of the long branch of the incus. 

 This articulation presents also cartilages of in- 



crustation, and a minute synovial capsule, to- 

 gether with strengthening ligamentous fibres. 



Fig. 251. 



The small bones connected together, and their relation 

 to the osseous labyrinth. Left side. Magnified. 

 (From Soemmerring . ) 



Muscles of the small bones. Some anatomists 

 admit four muscles : three attached to the mal- 

 leus and one to the stapes. Of the three at- 

 tached to the malleus,two are described as having 

 for their action the relaxation of the membrana 

 tympani; but these so called laxatores tym- 

 pani are merely ligaments, and have been de- 

 scribed above as such. I agree with Hagen- 

 bach,* Breschet,t and Lincke,} that two muscles 

 only can be distinctly demonstrated, and these 

 two are both tensors of the tympanum. A 

 relaxation, or state of rest of the membrana 

 tympani, takes place of itself, as Treviranus 

 remarks, when the tensors cease to act; hence 

 a relaxator muscle of the membrana tympani 

 was not required 



Muscle of the malleus, musculus internus 

 mallei s. tensor tympani. This muscle occupies 

 the canal, or half canal, which was described as 

 lying above the osseous part of the Eustachian 

 tube. It arises from the posterior and under 

 part of the sphenoid bone, from the superior 

 part of the cartilaginous portion of the Eusta- 

 chian tube, and also from an aponeurotic sheath 

 which lines the canal, or completes the groove 

 in which it is lodged. Its fibres proceed from 

 before backwards, and terminate in a slender 

 tendon, which bending at a right angle, as a 

 rope over a pulley, enters the cavity of the 

 tympanum, through the tubular projection al- 

 ready described as a continuation of the canal 

 in which it lies. Having entered the tympanum, 

 it proceeds outwards, and is inserted into a 

 slight elevation, sometimes remarked on the 

 inner and anterior surface of the handle of the 

 malleus below the long process, and also a 

 little below and opposite the root of the short 



* Disquisitiones anatomicae circa rausculos auris 

 uiternae hominis et Mammalium, &c. Basileae, 1833, 

 p. 20. 



t Op. cit. s. xxxiii. 



\ Das Gehbrorgan, &c. Leipzig, 1837, p. 140, 

 s. 114. 



Biologic, Band. vi. p. 376. 



