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An experimental study of the accessory optic system and of other optic fibers in the opossum, Didelphis Virginiana
Author(s) -
Giolli Roland A.
Publication year - 1965
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.901240208
Subject(s) - opossum , biology , optic tract , optic chiasma , anatomy , lateral geniculate nucleus , didelphis , marsupial , neuroscience , zoology , optic nerve , visual cortex
A study of experimental degeneration of the accessory optic system in a primitive mammal, the opossum, was undertaken in order the clarify several points regarding fiber organization and to allow comparisons to be made with this system in more advanced mammals and non‐mammalian vertebrates. The other portions of the optic system were also studied but not in great detail, since the findings were in basic agreement with those of Bodian ('37) in opossum. An eye was enucleated in each of five opossums which was sacrificed 7–12 days later. The Nauta‐Gygax technique was used to show that in opossum the accessory optic system consists essentially of one pair of tracts and terminal nuclei. Fibers of this system cross in the optic chiasma and leave the optic tract midway between the chiasma and the lateral geniculate nucleus to course caudally on the surface of the medial third of the cerebral peduncle. They intermingle with the fibers of the superficial division of the tractus geniculatus descendens and then enter the nucleus of the transpeduncular tract to terminate. The findings on the structure of the accessory optic system in opossum are in basic agreement with those in reptiles and birds. Comparison with studies in more advanced mammals indicates that this system has undergone striking changes in the topographical organization of its fibers.