96
JAMES CLARICE FENWICK
Kappers, 1965) before reaching the roof of the diencephalon. Efferent
fibers originating within the central nervous system and ending on pineal
cells have rarely been described (Van de Kamer, 1955; Hafeez and
Ford, 1967). These efferent fibers are probably the same type of aberrant
commissural fibers described in mammals ( Ariens Kappers, 1965).
Aside from a well-documented nervous connection between the pineal
body and the posterior commissure (Holt, 1891; Hill, 1894; StudniEka,
1905; Ariens Kappers, 1964; Rudeberg, 196813) relatively little is known
of the central terminations of the pineal nerve (tractus epiphyseos of
Ariens Kappers, 1965 ) . Possible connections have been suggested with
the superior commissure (Holt, 1891), and with the right habenular
nucleus (Ariens Kappers, 1964) as well as other habenular structures
(Holt, 1891; N. Holmgren, 1918b). In one case only, fibers have been
described as running to the optic tectum (N. Holmgren, 1918~). Some
workers have suggested a link between the pineal body and the subcommissural organ (Dendy, 1907; U. Holmgren, 1959a), but this is
apparently not present in all fishes. Le Gros Clarke (1932) believes
that the pineal organ of cyclostomes is heavily supplied with olfactory
input channels and this possibility should be investigated. Notwithstanding the paucity of information concerning the exact site(s) of
the pineal nerve terminations, connections already described could permit a link between the pineal body and the efferent centers of the brain
through which the pineal body could influence various integrative afferent
centers ( Ariens Kappers, 1965). Further information on the innervation
of the fish pineal gland together with the phylogenetic implications and
earlier bibliographies may be consulted in the excellent papers of U.
Holmgren (1959a) and Ariens Kappers (1965).
1V. PHYSIOLOGY OF THE PINEAL BODY
Although neurophysiological studies have proved that the pineal
organ of Salmo gairdneiri irideus is responsive to illumination (Dodt,
1963; Morita, 1966) there is only scanty literature on the actual physiology of the pineal organ in fishes. Active cellular metabolism has been
indicated by at least two authors (Palayer, 1958; U. Holmgren, 1959b)
who studied the uptake of radioactive phosphorus by the fish pineal.
Recently, interest has been directed toward the possible presence of
melatonin and other tryptophan derivatives within the fish pineal (Quay,
1965; Oksche and Kirschstein, 1967; Oguri et al., 1968; Rudeberg,
1968b ) . Quay ( 1965) localized the enzyme hydroxyindole-O-methyl
JAMES CLARICE FENWICK
Kappers, 1965) before reaching the roof of the diencephalon. Efferent
fibers originating within the central nervous system and ending on pineal
cells have rarely been described (Van de Kamer, 1955; Hafeez and
Ford, 1967). These efferent fibers are probably the same type of aberrant
commissural fibers described in mammals ( Ariens Kappers, 1965).
Aside from a well-documented nervous connection between the pineal
body and the posterior commissure (Holt, 1891; Hill, 1894; StudniEka,
1905; Ariens Kappers, 1964; Rudeberg, 196813) relatively little is known
of the central terminations of the pineal nerve (tractus epiphyseos of
Ariens Kappers, 1965 ) . Possible connections have been suggested with
the superior commissure (Holt, 1891), and with the right habenular
nucleus (Ariens Kappers, 1964) as well as other habenular structures
(Holt, 1891; N. Holmgren, 1918b). In one case only, fibers have been
described as running to the optic tectum (N. Holmgren, 1918~). Some
workers have suggested a link between the pineal body and the subcommissural organ (Dendy, 1907; U. Holmgren, 1959a), but this is
apparently not present in all fishes. Le Gros Clarke (1932) believes
that the pineal organ of cyclostomes is heavily supplied with olfactory
input channels and this possibility should be investigated. Notwithstanding the paucity of information concerning the exact site(s) of
the pineal nerve terminations, connections already described could permit a link between the pineal body and the efferent centers of the brain
through which the pineal body could influence various integrative afferent
centers ( Ariens Kappers, 1965). Further information on the innervation
of the fish pineal gland together with the phylogenetic implications and
earlier bibliographies may be consulted in the excellent papers of U.
Holmgren (1959a) and Ariens Kappers (1965).
1V. PHYSIOLOGY OF THE PINEAL BODY
Although neurophysiological studies have proved that the pineal
organ of Salmo gairdneiri irideus is responsive to illumination (Dodt,
1963; Morita, 1966) there is only scanty literature on the actual physiology of the pineal organ in fishes. Active cellular metabolism has been
indicated by at least two authors (Palayer, 1958; U. Holmgren, 1959b)
who studied the uptake of radioactive phosphorus by the fish pineal.
Recently, interest has been directed toward the possible presence of
melatonin and other tryptophan derivatives within the fish pineal (Quay,
1965; Oksche and Kirschstein, 1967; Oguri et al., 1968; Rudeberg,
1968b ) . Quay ( 1965) localized the enzyme hydroxyindole-O-methyl