in the Whale-bone Whale. 87 
no other opening into it by which it can communicate exter- 
nally. 
Within the cavity of the tympanum, close to the bony rim 
to which the membrana tympani is attached, there is a mem- 
branous fold fixed at one end to the centre of a slight protu- 
berance on the concave surface of the large hollow bone, and 
stretched across the cavity, its loose upper edge forming a 
line across the centre of the hollow of the membrana tympani, 
the other end passing beyond the cavity to be attached to the 
short handle of the malleus, which is situated immediately 
behind the membranous lining of the tympanum. The long 
handle of the malleus is left loose. The incus and stapes have 
the same relative situation to one another as in the human ear,, 
differing in nothing but being contained in a cavity distinct 
from that of the tympanum. The appearance of an os orbicu- 
lare is wanting. 
The other parts of the organ, the vestibulum, semi-circular 
canals and cochlea, and the meatus internus through which 
the nerves from the brain pass to be distributed to these parts, 
do not differ materially from what is mot with in the human 
ear. As the parts which have been described are delineated 
in the annexed drawings, I have been less minute in my descrip- 
tion than I should have otherwise thought it necessary to be. 
From the mechanism which has been described, it is evi- 
dent that the impulses made on the membrana tympani are 
not immediately communicated to the ossicula auditus as in 
other animals ; they are only communicated to the tympanum 
and thence to the chord stretched across its cavity. 
The membrana tympani by its muscular structure has the 
means within itself of adjustment to different sounds, while. 
