THE SONG OF FISHES. 
345 
fig. 4) of the air-bladder.* M. Dufosse has established the 
curious fact that, in the majority of cases, it is not the totality of 
the fleshy bundles of the intracostals which contract to produce 
sound, but only that portion of the muscular surface which is in 
immediate contact with the air-bladder ; and that, under these 
circumstances, whatever organs, whether bony or otherwise, are 
acted upon by these muscles, come only into play as accessories 
to the production and propagation of sound. 
Let us now briefly consider the second of the two methods of 
the production of “ commensurable ” sounds. Here the air- 
bladder is itself “a generator of sounds, as completely inde- 
pendent of the rest of the organism of the fish as any other 
apparatus of 4 psophosis,’ f or even of phonation with which the 
animal may he endowed.” After placing a gurnard on its 
hack, making a long incision in the abdominal walls, and care- 
fully drawing aside any viscera which may obstruct the view, if 
the tip of a finger be held in contact with the air-bladder, 
vibration will be felt exactly synchronous with, and having the 
same intensity as the sounds produced by the fish. This can be 
further proved by means of a stethoscope applied to this organ. 
Further than this the air-bladder will be seen, during the 
emission of such sounds, to be affected by movements which 
may either throw the organ into folds or subject it to a greater 
tension in various parts; and this even to such a degree as 
somewhat to alter its general shape. Having isolated the organ 
as much as possible by delicate yet rapid manipulation from the 
rest of the body, with the exception of the vessels and nerves 
which pass to it, let a stethoscope, provided at its mouth with a 
diaphragm of gold-beater’s skin, be applied to the anterior part 
of the organ ; then let the nerves which pass to the latter be 
severed, first on one side and then on the other, when it will be 
found that the sound first decreases in intensity, and finally 
ceases altogether. From this and other experiments M. Dufosse 
concludes that the air-bladder, in the majority of the gurnard 
family — 
a. Is a physiological organ, which, whatever may be its 
other functions, is a generator of sounds. 
/?. That its 44 intrinsic ” muscles, by their vibration, aided 
and intensified by the rest of the organs, are the agents of such 
sounds. 
* The anatomist Stannius mentions, among other branches of the pneu- 
mogastric nerve, certain which run “ inter membranas vesicse natatorise. Inde 
ab cesophago in ductu ad vesicam decurrentes hanc ipsam adsequuntur. 
Fibrce hce nerxece omnes colore niveo ceteris excellunt. ( Symbolic ad Anatomiam 
piscium. Rostochii : 1839.) 
t This is a word coined by Duges. It appears to be derived from -<\>6^oq 
(Lat. strepitus ), any articulate sound, as opposed to <pwvi). 
