54
JERALD J . BERNSTEIN
prolonged inability of the fish to orient itself. This was manifested by
the animal lying on one side following periods of stimulation (Clark
The stimulus-rebound phenomena is found in all classes of vertebrates. It would appear then, that the mechanisms of cerebellar function
have evolved early. The function of the cerebellum in fish has yet to be
completely defined. These preliminary results, however, do indicate that
the cerebellum is involved with the maintenance of muscle tonus in the
anirnal, postural reflexes, and integration of visual, acoustic, and perhaps
gustatory stimuli.
et az., 1960).
VII. MEDULLA OBLONGATA
A. Anatomy
The boundary between medulla oblongata and spinal cord in fish is
indistinct ( Ariens Kappers et al., 1960; Aronson, 1963; Papez, 1929),
and it is not surprising, therefore, to find that the mcdulla can be easily
divided into columns of nerve fibers based on the type of information
transmitted. Thus, there are somatic and visceral sensory columns, and
somatic and visceral motor columns. The somatic sensory column carries
information derived from general sensory, cutaneous, vestibular, lateral
line, and trigeminal (Cr.N.V) nerve fibers. These nerve complexes comprise the cutaneous sensory nerves arising from the medulla, are proprioceptive on extroceptive in function, and can be classified according
to the type of information carried by the composite nerve fibers in the
cranial nerves (Fig, 8 ) . The visceral sensory column carries nerve fibers
which are derived from the nerves of chcmoreceptors (taste) and nerves
arising in the viscera. This column is formed by the combined centers
and nerve fibers which are the sensory branches of the facial (Cr.N.VII),
glossopharyngeal ( Cr.N.IX), and vagus cranial ncrves (Cr.N.X). Nerve
fibcrs in this category function in the transmission of introccptive information. There are, in addition, two motor columns: thc visceral motor
column that carries efferent motor nerve fibers derived from the facial,
glossopharyngeal, and vagus nerves, and a somatic motor column that
carrics efferent ncrve fibers to the ocular musclcs and musclcs of the
pharyngeal complex. The visceral motor components are effcrcnt to thc
glands and musculature of the viscera. Thcsc nerve fibcw arc. motorsecretory, visceral motor, and vasomotor in function. Included in this
efferent outflow are nerve fibers in the vagus nerve that are visccral
I
JERALD J . BERNSTEIN
prolonged inability of the fish to orient itself. This was manifested by
the animal lying on one side following periods of stimulation (Clark
The stimulus-rebound phenomena is found in all classes of vertebrates. It would appear then, that the mechanisms of cerebellar function
have evolved early. The function of the cerebellum in fish has yet to be
completely defined. These preliminary results, however, do indicate that
the cerebellum is involved with the maintenance of muscle tonus in the
anirnal, postural reflexes, and integration of visual, acoustic, and perhaps
gustatory stimuli.
et az., 1960).
VII. MEDULLA OBLONGATA
A. Anatomy
The boundary between medulla oblongata and spinal cord in fish is
indistinct ( Ariens Kappers et al., 1960; Aronson, 1963; Papez, 1929),
and it is not surprising, therefore, to find that the mcdulla can be easily
divided into columns of nerve fibers based on the type of information
transmitted. Thus, there are somatic and visceral sensory columns, and
somatic and visceral motor columns. The somatic sensory column carries
information derived from general sensory, cutaneous, vestibular, lateral
line, and trigeminal (Cr.N.V) nerve fibers. These nerve complexes comprise the cutaneous sensory nerves arising from the medulla, are proprioceptive on extroceptive in function, and can be classified according
to the type of information carried by the composite nerve fibers in the
cranial nerves (Fig, 8 ) . The visceral sensory column carries nerve fibers
which are derived from the nerves of chcmoreceptors (taste) and nerves
arising in the viscera. This column is formed by the combined centers
and nerve fibers which are the sensory branches of the facial (Cr.N.VII),
glossopharyngeal ( Cr.N.IX), and vagus cranial ncrves (Cr.N.X). Nerve
fibcrs in this category function in the transmission of introccptive information. There are, in addition, two motor columns: thc visceral motor
column that carries efferent motor nerve fibers derived from the facial,
glossopharyngeal, and vagus nerves, and a somatic motor column that
carrics efferent ncrve fibers to the ocular musclcs and musclcs of the
pharyngeal complex. The visceral motor components are effcrcnt to thc
glands and musculature of the viscera. Thcsc nerve fibcw arc. motorsecretory, visceral motor, and vasomotor in function. Included in this
efferent outflow are nerve fibers in the vagus nerve that are visccral
I