0. LOWENSTEIN
218
tracted asymmetry in the tonus of the horizontal eye muscles. This asymmetry could be augmented by ipsilateral and diminished by contralateral
horizontal rotation, a fact furnishing further evidence for the basic bidirectionality of the semicircular canal mechanism ( Lowenstein, 1937).
2. THE OTOLITH ORGANS
The prototype for the otolith organ is fully elaborated in the invertebrate statocyst, and gravity perception is one of the fundamental factors
in animal orientation. It is interesting, however, that an auditory function
was originally attributed to all so-called otocysts. Eimer (1878) and
Romanes (1885) were the first to apply the newly discovered equilibrium
function of the vertebrate ear to the lithocysts of medusae, attributing
to them, in addition to their assumed auditory function, the regulation
of locomotory movements.
In the vertebrates the detailed study of the mode and function of the
otolith organs has all along been handicapped by their inaccessibility to
separate elimination or stimulation. The operative interruption of the
nerve supply of individual otolith organs is generally almost impossible
because of the shortness of the nerve branches, and the removal of the
otoliths usually involves wide openings in the vestibular space with considerable endolymph loss and spread of the damage to all other parts of
the labyrinth. It is therefore not surprising that for a long time the functional analysis of the otolith organs was mainly based on the interpretation
of the spatial arrangement and the anatomic relationships of the otoliths
and their sensory epithelia, supplemented by rather contradictory results
of experiments with artificial mechanical and other stimulations carried
out in elasmobranchs by Kubo (1906) and Maxwell (1923) and in the
pike by Ulrich (1935).
When it became clear, however, that fish react to sound over a considerable range of frequencies (see below), and that their power of sound
perception and pitch discrimination is chiefly localized in the labyrinth,
the conclusion became inescapable that otolith organs must be capable of
gravity and sound perception alike. Apart from the fact that both sensory
functions imply sensitivity to linear acceleration, they are so different in
their biological significance that it was hard to believe that any single
one of the three otolith organs, namely, utriculus, sacculus, and lagena,
could combine both functions. The results of the search for a fundamental
division of labor among the three otolith organs in fishes can be summarized as follows. In the elasmobranch Mustelus canis (Parker, 1909; Maxwell, 1923), in the bony fish, Pseudopleuronectes americanus ( Lyon,
1899), and in Carassius auratus ( Manning, 1924), Cynoscion regalis
218
tracted asymmetry in the tonus of the horizontal eye muscles. This asymmetry could be augmented by ipsilateral and diminished by contralateral
horizontal rotation, a fact furnishing further evidence for the basic bidirectionality of the semicircular canal mechanism ( Lowenstein, 1937).
2. THE OTOLITH ORGANS
The prototype for the otolith organ is fully elaborated in the invertebrate statocyst, and gravity perception is one of the fundamental factors
in animal orientation. It is interesting, however, that an auditory function
was originally attributed to all so-called otocysts. Eimer (1878) and
Romanes (1885) were the first to apply the newly discovered equilibrium
function of the vertebrate ear to the lithocysts of medusae, attributing
to them, in addition to their assumed auditory function, the regulation
of locomotory movements.
In the vertebrates the detailed study of the mode and function of the
otolith organs has all along been handicapped by their inaccessibility to
separate elimination or stimulation. The operative interruption of the
nerve supply of individual otolith organs is generally almost impossible
because of the shortness of the nerve branches, and the removal of the
otoliths usually involves wide openings in the vestibular space with considerable endolymph loss and spread of the damage to all other parts of
the labyrinth. It is therefore not surprising that for a long time the functional analysis of the otolith organs was mainly based on the interpretation
of the spatial arrangement and the anatomic relationships of the otoliths
and their sensory epithelia, supplemented by rather contradictory results
of experiments with artificial mechanical and other stimulations carried
out in elasmobranchs by Kubo (1906) and Maxwell (1923) and in the
pike by Ulrich (1935).
When it became clear, however, that fish react to sound over a considerable range of frequencies (see below), and that their power of sound
perception and pitch discrimination is chiefly localized in the labyrinth,
the conclusion became inescapable that otolith organs must be capable of
gravity and sound perception alike. Apart from the fact that both sensory
functions imply sensitivity to linear acceleration, they are so different in
their biological significance that it was hard to believe that any single
one of the three otolith organs, namely, utriculus, sacculus, and lagena,
could combine both functions. The results of the search for a fundamental
division of labor among the three otolith organs in fishes can be summarized as follows. In the elasmobranch Mustelus canis (Parker, 1909; Maxwell, 1923), in the bony fish, Pseudopleuronectes americanus ( Lyon,
1899), and in Carassius auratus ( Manning, 1924), Cynoscion regalis