268 
PROFESSORS T. W. BRIDGE AND A. C. HADDON 
sacculi, A similar function may possibly be assigned to the receptaculum dorsale 
described by us in Macrones nemurus.'^ 
No differential action of the two sacculi can possibly take place, at all events so far 
as impulses received through the Weberian mechanism are concerned, since the only 
channel through which any movement initiated in the fluids of the atrial cavities by 
the motion of the Weberian ossicles can reach them is the median and unpaired sinus 
endol}miphaticus ; hence it must follow that each sacculus will be affected by any 
such disturbances to an equal extent and at the same moment. 
It may be well to emphasize the fact that, whatever may be the force which sets 
the Weberian ossicles in motion, there are no obvious adaptations for increasing its 
intensity in the course of transmission to the sensory epithelium of the inner ear, and 
if, as we believe will prove to be the case, it is the variations in the volume of the gas 
contained in the air-bladder under the influence of different hydrostatic pressures, 
which condition the lateral expansion or contraction of the anterior chamber, it is 
obvious that the force exerted on the Weberian ossicles will be too considerable for 
there to be any use of increased leverage in order to augment the impulse imparted 
to the fluids of the internal ear. We shall again refer to this point in discussing 
Weber’s auditory theory of the function of these ossicles. 
On the whole, and apart from any predisposition in favour of any particular theory, 
the impression left upon our minds by a consideration of the extent to which the 
physiology of the Weberian mechanism is conditioned by the more obvious features 
in its structure and relations to the air-bladder is, that ii is not adapted for the 
transmission of the smaller changes of whatever nature that may take place in the 
condition of the gaseous contents of the air-bladder ; still less is the mechanism 
adapted for the transmission of any rapid vibratory impulses that may be com- 
municated to the contained gases ; on the contrary, the mechanism would seem to be 
admirably fitted to acquaint the Fish with the occurrence of the grosser volumetric 
variations that from time to time may affect the entire gaseous contents of the air- 
hladder. 
2. The second point for consideration is — to which of the several known functions of 
the air-bladder and internal ear are the Weberian ossicles to be regarded as accessory 
structures. 
As we have already pointed out, an initial difficulty in the way of any attempt to 
solve this question is the complex physiological character of the two organs which 
the Weberian ossicles bring into functional relations. At least two distinct func- 
tions must be considered in connection with the auditory organ, (l) audition, and 
(2) equilibration, or orientation ;t while the air-bladder in different Fishes is even more 
complex in function, more so possibly than any other organ. Among the various uses 
* See p. 81. 
t As a sequel to the researches of Goltz and others among Vertebrata, mention may be made of the 
fact that Delage (11) and Engelmann (12) have shown that it is highly probable that the so-called 
