Bauhaus-Universität Weimar

756 
TENSION OP THE MEMBRANA TYMPANI. 
The long process of the malleus, receives the undulations of the 
membrana tympani and of the air in a direction nearly perpendicular 
to itself. The undulations maintain this direction through the whole 
chain of ossicula quite independently of its direction, and of that of the 
individual bones forming it. From the long process of the malleus the 
undulations are propagated to its head, which projects from it at an 
angle; thence into the incus the long process of'which has a direction 
parallel with the long process of the malleus. From the long process 
of the incus the undulations are communicated to the stapes, which is 
united to it at right angles. All these changes in the direction of the 
chain of bones have no influence on that of the impulse, which remains 
the same as it was in the meatus externus and long process of the 
malleus, so that the undulations are communicated by the stapes to the 
fenestra ovalis in a perpendicular direction. 
Tension of the membrana tympani. 
IV. J1 membrane of small extent propagates sound better in the lax con¬ 
dition than when made very tense. 
The inquiry respecting the capability of the membrana tympani ta 
conduct sound better in its lax or in its tense condition, may be made 
to embrace membranes generally. We must, however, distinguish here 
between reciprocation of sonorous vibrations, resonance, and conducting 
power. The reciprocation of sounds is a phenomenon which bodies 
rendered elastic by tension are not capable of manifesting in their lax 
condition. 
The result was in all my experiments the same. The sound was 
transmitted with much greater intensity through the lax membrane than 
through the membrane made tense by raising the outer extremity of the 
rod. A watch may be used as the source of the sound in these experi¬ 
ments. But every noise is heard louder when the membrane is lax; 
and its intensity diminishes in proportion as the tension of the membrane 
is increased. 
The membrana tympani in one’s own person may, however, be ren¬ 
dered tense so as to produce this influence on the insensity of sounds 
at will. In the dead subject, the membrana tympani may be rendered 
more tense in two ways besides by the retraction of the malleus; namely, 
by exhausting the air in the tympanum by sucking through the Eusta¬ 
chian tube, and by forcing more air into the tympanum through the 
same canal. In the first case, the membrana tympani is pressed in¬ 
wards. In the second case, it is forced outwards; the long process of 
the malleus, however, not being 'displaced by the pressure of the air 
within the tympanum, the centre of the membrane is prevented from 
changing its position, while the rest of it is protruded. 
But the$e modes of tension of the membrana tympani may be prac¬ 
tised in the living body also, and in the experiment on our own persons, 
namely, by a strong and continued effort of expiration while the mouth 
and nostrils are closed, or by a strong and long-continued effort of in¬ 
spiration under the same circumstances. In the first case, the com¬ 
pressed air is forced with a whizzing sound in the tympanum, and 
immediately hearing becomes indistinct. The same temporary imper-
        

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