OSSICLES OF THE EAK. 211 



and its oval base is applied to the fenestra ovalis. Surround- 

 ing the base of the stapes, is a ring of elastic fibre-cartilage, 

 which is closely united to the bony wall of the labyrinth, by 

 an extension of the periosteum over the base of the stapes. 



" The relation of the stirrup to the anvil is such that, if 

 the handle of the hammer be drawn inward, the long process 

 of the anvil presses firmly against the knob of the stirrup ; 

 the same takes place if the capsular ligament between both 

 be cut through." 1 



The articulations between the malleus and the incus and 

 between the incus and the stapes are so arranged that when 

 the membrana tympani is forced outward, as it may be by in- 

 flation of the tympanic cavity, there is no danger of tearing 

 the stapes from its attachment to the fenestra ovalis ; for, 

 when the handle of the malleus is drawn outward, the cog- 

 joint between the malleus and the incus is loosened and no 

 great traction can be exerted upon the stapes. 



The fact that the stapes may be pressed against the liquid 

 of the labyrinth was demonstrated by a very satisfactory ex- 

 periment described by Helmholtz, in which an opening, made 

 into the superior semicircular canal, was fitted with a slender 

 glass tube, and the vestibule and a portion of the tube filled 

 with water. " The movements oi the bones of the ear pro- 

 duced by forcing air into the external meatus caused the fluid 

 in the tube to rise O9 mm." From this experiment, it was 

 calculated that the excursions of the stapes amounted to from 



:rhr to -sfa of an mcn - a 



Although the experiments which we have cited illustrate 



pretty conclusively the mechanism of the ossicles and the ac- 

 tion of the tensor-tympani muscle, both as regards the chain 

 of bones and the membrana tympani, direct observations 



v l HELMHOLTZ, op. cit. t p. 43. 



2 Op. cit., p. 43. 



The movements of the stapes have been described by Dr. A. H. Buck, in an 

 elaborate paper. The details of his experiments, however, are very minute, and 

 the facts stated above are sufficient for our purpose. (BUCK, On the Mechanism 

 of the Ossicles of the Ear, New York, 1870.) 



