THE EAR AND HEARING. 
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In u (full) the ground tone is heard alone ; 
,, o (oh) the next octave is audibly combined with the 
ground tone ; 
,, e (get) the ground tone is strongly mingled with the 
second octave above ; 
,, i (bit) the ground tone is weaker, and the second and 
fourth octaves above strong ; 
,, a (oh) the ground tone is modified by the marked 
presence of the fifth, sixth, and seventh octaves 
above. 
He applies a similar principle to explain differences in the 
consonant sounds; but in these the distinctions are 
generally so palpable that the different shocks they cause to 
the nerve of hearing seem generally a sufficient explanation. 
The theory of Helmholtz may be summarised thus:— 
I. —That what appears to us to be a simple sensation of 
tone is a composite mass of sensations resulting from a fusion 
of a ground tone and several feebler upper tones, each of 
these elements being transmitted by a distinct nerve fibre, 
and that each individual tone is itself the produce of hundreds 
or even thousands of vibrations, each probably causing some 
physical change in the nerve of hearing, though not suffi¬ 
ciently intense to rise into consciousness. 
II. —The harmony of tv^o tones is referred to the purely 
negative condition of non-disturbance between the prominent 
upper tones of the two notes—or that harmony arises from 
the union of two masses of tone, each of which affects a 
plurality of nerve fibres, and the elements of which are in no 
case so near to one another as to produce intermittent shocks 
of tone. That is to say, that just as a single musical clang 
is demonstrated to be an enormously complex product, so 
harmony is proved to be a more complex product of this 
product ; and finally, that the pure pleasure of melody arises 
from the presence in sequent clangs of some common tonic 
element which serves to bind them together by a simple bond 
of sensuous resemblance. 
Auditory spectra or subjective sounds such as singing, 
buzzing, ticking, snapping, humming, &c., accompanying 
overwork and disease, the noise persisting after reviews, 
railway, coach, or steamship travelling, &c., arise from 
disease of the brain or nerve, pressure of congested blood 
vessels upon the auditory nerve, over-stimulation of the 
nerve, inducing a temporary morbid condition, obstructions 
in the tympanum, Eustachian tube, &c., and seem to prove 
conclusively that sound (like other sensations) is essentially a 
state of a special nerve (here the auditory) excited externally 
