350 Prof. A. M. Mayer’s Haperiments on the supposed 
with the theorem of Fourier, reasoned that there must be a 
cause for it in the very dynamic constitution of the ear; and 
the previous discovery by the Marquis of Corti of several 
thousand* rods of graded sizes in the ductus cochlearis, indi- 
cated to Helmholtz that these were suitable bodies to effect the 
decomposition of a composite sonorous wave by their covibrating 
with its simple harmonic elements. This supposed function of 
the Corti organ gave a rational explanation of the theorem of 
Ohm, and furnished “a leading-thread ” which conducted Helm- 
holtz to the discoveries contained in his renowned work Die 
Lehre von den Tonempfindungen+. In this book he first gave 
the true explanation of timbre, and revealed the hidden cause 
of musical harmony, which, since the days of Pythagoras, 
had remained a mystery to musicians and a problem to philo- 
sophers. 
It may perhaps never be possible to bring Helmbholtz’s hypo- 
thesis of the mode of audition in the higher vertebrates to the 
test of direct observation, from the apparent hopelessness of 
ever being able to experiment on the functions of the parts of 
the inner ear of mammalia. The cochlea, tunnelled in the hard 
temporal bone, is necessarily difficult to dissect ; and even when 
a view is obtained of the organ of Corti, its parts are rarely 
in situ, and often they have already had their natural structure 
altered by the acid with which the bone has been saturated to 
render it soft enough for dissection and for the cutting of sec- 
tions for the microscope. 
As we descend in the scale of development from the higher 
vertebrates, we observe the parts of the outer and middle ear 
disappearing, while at the same time we see the inner ear 
gradually advancing toward the surface of the head. The 
external ear, the auditory canal, the tympanic membrane, and 
with the latter the now useless ossicles, have disappeared in 
the lower vertebrates, and there remains but a rudimentary 
labyrinth. 
* According to Waideyer, there are 6500 inner and 4500 outer pillars in 
the organ of Corti. 
+ “ But all of the propositions on which we have based the theory of 
consonance and dissonance rest solely on a mmute analysis of the sensa- 
tions of the ear. This analysis could have been made by any cultivated 
ear without the aid of theory; but the leading-thread of theory and the 
employment of appropriate means of observation have facilitated it im an 
extraordinary degree. 
“Above ail things I beg the reader to remark that the hypothesis on the 
covibration of the organs of Corti has no immediate relation with the ex- 
planation of consonance and dissonance, which rests solely on the facts of 
observation, on the beats of harmonics and of resultant sounds.”’—Helm- 
holtz, Tonempfindungen, p. 342. 
