A. M. Mayer— Researches in Acoustics. 105 
a fine duct. The arch of Corti rests upon the membrana 
basilaris, which extends beyond the base of the arch to the 
membranous outer wall of the cochlea, and over the arch 
<a the membrana tectoria, covering the rods of Corti and 
the hair-cell cords as with a roof, but leaving the outer portion 
of the elastic membrana basilaris exposed. e will now show 
that the significance of these anatomical relations is to bring the 
sound vibrations to act with the greatest advantage on the 
co-vibrating parts of the ear, and to cause these parts to make 
one-half as many vibrations in a given time as the tympanic or 
basilar membranes. 
The relations which the form of the scale bears to the sono- 
rous waves traversing them, will be modified according to the 
existence or non-existence of a communication between the 
scale. On this point there seems to be some difference of 
opinion, and, therefore, I will attempt to explain the functions 
of the scale, first, on the supposition that they are continuous, 
and then on the assumption that they are not continuous, but 
closed at the place where the helicotrema is supposed by most 
. 
anatomists to exist. 
canal but little difference in phase, and therefore but little 
I action. Now the united lengths of the scalw is but a 
small fraction of the mean length of the sonorous waves which 
traverse it; for if we take, as above, 4} meters as the mean 
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