ACCESSORY ORGANS OF HEARING 67 



would pass out througli tlic slit-like aperture and be received by 

 the otolith Ij'ing on the hair-colls close to this orifice and so to the 

 auditory ganglion. The membrane tends to take a somewhat 

 spiral course in the anterior capsule, so that the relative size of the 

 two compartments vary ; the inner division being large at the base 

 and the outer division being large at the apex. If this view be 

 correct the anterior vesicle Mould appear to be constructed some- 

 what on the plan of a rudimentary cochlea. 



We regard the connection with the swim-bladder as simply a 

 means of regulating the pressure of gases in the system of air- 

 vesicles. The theory of an auditory function attributed to this 

 mechanism is nothing new. This was the view expressed by most 

 of the older writers. Weber considered that the septum in the 

 anterior osseous capsule functioned as a tympanic membrane. 

 Another theory held that the mechanism is part of a reflex system 

 which through efferent \nsceral nerves transmits impulses to the 

 swim-bladder, in order to adjust it to changes in hydrostatic pressure. 

 Another modern and very careful anatomist does not consider the 

 posterior air vesicle of any importance ; he dismisses it with the 

 statement, " Since the posterior vesicle has no apparent relation to 

 the labyrinth or other structure outside the bony capsule it will not 

 be discussed further in this paper." 



Other objections have been raised to the theory which has been 

 expounded above, namely, the slight variations in the posterior 

 vesicle found in the pilchard and sprat. But we consider these 

 variations do not invalidate our view and hold that the herring 

 presents the most perfect adaptation of the accessory auditory 

 system to the function of hearing to be found in the family of 

 Clupeoids. 



