224 JOURNAL OF THE PLYMOUTH INSTITUTION. 
THE HUMAN EAR. 
BY MRE. W. SQUARE, F.R.C.S. 
(Read November Ist, 1877.) 
TE ear is more analogous in ultimate structure to the eye than 
any other organ of the human body. It is firmly encased in the 
hardest portion of the temporal bone, to keep it away from external 
disturbing shocks. It is not like the eye, so regularly arranged ; 
but this is due to its having sound-waves instead of light to deal 
with. The membrana tympanum is the vibrating drumhead which 
receives the shocks. They are then transmitted by a chain of 
bones (the malleus, incus, and stapes) to the fenestra ovalis. The 
joint of the stapes here is elaborate, and capable of high range of 
movement. The bones and two membranes are moved by small 
muscles. The most interesting motion is the rendering tense the 
membrane of the fenestra ovalis, by fastening in the stapes. Inside 
this orifice is placed the labyrinth. It consists of a chamber, the 
utriculus, with appendages; the cochlea—semicircular canals, 
ampulle, sacculus, macula accoustica, &c. These are chiefly 
covered with epithelium, in which the various filaments of the 
auditory nerve have appropriate endings. The cochlea is a most 
intricate piece of machinery, containing the most elaborate organs. 
It has two canals, the scala tympani and vestibuli. .The latter has 
within it, and only divided from it by the membrane of Reisner, 
the ductus cochlearis. This contains the membrana tectoria and the 
organ of Corti. This latter has fibres, which being joined together 
at the capitula, form a tunnel. Over this is spread out the 
membrana reticularis, which has entangled in it the brushes of « 
auditory hairs belonging to the six cells arranged over the membrana 
basilaris. These hair cells in their action are the analogues of the 
rods and cones of the bacillary layer of the retina, multipliers of 
molecular disturbance. Roughly speaking, the functions of the 
various parts are supposed to be as follows: The tympanum for 
intensity, the cochlea for pitch, and the semicircular canals for 
direction. The whole is very complex, rendering verifying experi- 
ments exceedingly tedious and difficult. 
