274 
PROFESSORS T. W. BRIDGE AND A. 0. HAD DON 
organ are too thick to admit of their vibrating synchronously witl) rapidl}'- recurring- 
sound waves. This objection may- certainly be emphasized in those instances in which 
the walls of the air-bladder ai-e specially thickened where alone their vibi-ation can be 
conceived as likely' to produce corresponding movements in the Weberian ossicles, viz., 
the lateral walls of the anterior chamber. And, moreover, in the case of all the 
remaining families of Ostariophyseae, where the anterior chamber is not specially 
damped in particular regions through contiguity with suitably modified portions of the 
skeleton, its walls would probably vibrate to an equal extent in all directions, but, as 
only those vibrations which affect the lateral walls, or take place transversely, are 
competent to impart their motion to the Weberian ossicles, there must, in such cases? 
be a considerable loss in the intensity of the final effect produced on the internal ear ; 
and, hence, in dealing with the question of the fitness of the walls of the bladder to be 
affected by, or to transmit to the Weberian ossicles, delicate wave impulses in the 
contained gases, we cannot but regard this objection as a serious one. 
(c.) It may be further objected that the Weberian ossicles do not satisfy the neces- 
sary conditions required in a series of movably articulated ossicles adapted for the 
transmission of sound vibrations by vibrating as a rigid whole. In the, in some 
respects, analogous mechanism of the Mammalian tynnpanura the auditory ossicles 
directly articulate with one another without being in any way separated by a fibrous 
ligament of any description, and hence the ossicles are capable of vibrating as a rigid 
whole, synchronously with the sound vibrations that impinge on the tympanic 
membrane, and also of communicating such vibrations to the fluids of the inner ear. 
The Weberian ossicles, on the contrary, are but ill adapted for any such function. 
As we have previously pointed out, the inertia of the ossicles themselves, the mode 
of articulation of the tripodes with the centrum of the complex vertebra, which in 
some cases is affected by the actual continuity of their articular processes with the 
centrum in question, and more especially the interposition of a lax, or at all events 
compressible, ligament in the series of ossicles, are insuperable objections to any 
theory that requires that these structures should vibrate as a rigid whole, by rapidly 
recurring movements of slight amplitude, synchronously with the sound waves which, 
ex hypothesi, are produced in the gases of the air-bladder.* 
There are also other features in which the Weberian and true auditory ossicles may 
be compared and contrasted. With auditory ossicles there are almost always certain 
anatomical adaptations by means of which the effect produced at one end of the 
series by the direct impact of sound waves is considerably intensified at the other, 
where the ossicles are in direct relation with the fluids of the internal ear. This 
effect is usually brought about by the existence of marked disparity in the superficial 
areas of the tympanic membrane and the membrane of the fenestra ovalls, and, in 
addition in Mammalia, by the leverage of the ossicles themselves. In one respect 
the Weberian mechanism may be said to resemble auditory ossicles. The superficial 
* See also pp. 2G4, 2Go 
