ANIMAL MECHANISM. 297 



Small as the ossicula auditus are, the first and last 

 of the series have muscles, called tensors, laxators, &c, 

 which are susceptible of demonstration. Rough points 

 and projections on the inside of the tympanum, give at- 

 tachij|ent both to the muscles and the bones themselves. 

 Even these minute points, the old anatomists have 

 belabored with what they supposed significant names. 

 One end of the malleus, the handle, is connected with 

 the inside of the membrana tympani ; the other is fitted 

 into a socket of the inchus and that articulated with the 

 orbiculare or round bone, which stands as a medium 

 of connexion between the stapes or stirrup. 



Now such is the mechanical adaptation of one of these 

 bones to the other, that if the extreme point of the handle 

 of the malleus which, as befor* remarked, is joined to 

 the membrane, be moved the millionth or ten millionth 

 part of an inch, 7 by the vibrations of the drum head, it 

 will so operate on the inchus and then on the stapes, 

 through the intervention of the orbiculare, that the last 

 bone, will move through treble the space, by a single 

 sonorous pulsation of the malleus, in the same period of 

 time. In fact, the stirrup, in plain language, is exactly 

 fitted into the oval window, like the box of a pump, so 

 that a motion given to the handle of the malleus, operates 

 on the chain, to effect the stapes, that it may work back- 

 ward and forward, with the same motion and on the same 

 principle of the working of the piston of a syringe. To 

 hear, it is necessary that the stapes, attached to the 

 parchment window, should move to and fro, for a reason 

 hereafter to be explained, or no sensation can be convey 

 ed by the acoustic nerve to the brain. 



Gentlemen curious in these inquiries, can readily pick 

 out the ossicula auditis from the dry skulls of horses, 

 sheep, dogs and cats. There is a slight variation however 

 in form, and ultimately, in burrowing animals, a wide 

 departure in configuration from those in man. 



VESTIBULE. 



This word, implies a porch or entry, being an in- 

 termediate apartment between the tympanum and coch- 

 lea ; in the sense in which it is now received, it is a 



VOL. i. NO. xn. 26* 



