DISTRIBUTION OF OPTIC TERMINALS IN DIFFERENT OPTIC CENTRES OF FROG

The sites of termination of optic fibres were investigated with the Fink-Heimer method in the frog. Terminal degeneration was found in the following places. 1. (1) The contralateral nucleus Bellonci was totally invaded by optic terminals with a conspicuous accumulation of degeneration in the ventrolateral part of the nucleus. On the ipsilateral side degeneration occupied the dorsolateral part of the nucleus Bellonci. 2. (2) In the contralateral lateral geniculate body degenerated terminals distinctly outlined an ovoid area within degeneration was most dense in its dorsolateral part. On the ipsilateral side degeneration was confined to the dorsomedial part of this ovoid area. 3. (3) In the contralateral pretactal region degeneration was found in a cylindrical area which extended between the lateral and medial divisions of the optic tract, including a small medioventral extension of the dorsal end of the area. On the ipsilateral side only the medial third of this area contained degeneration. 4. (4) In the optic tectum degeneration was exclusively found on the contralateral side. Degenerated terminals were arranged in four indistinct sheets in layers 9 and 8. 5. (5) A small bundle of optic fibres could be followed to the nucleus ectomammillaris in the contralateral tegmentum. The existence of retino-hypothalamic connections assumed by previous authors could not be verified. © 1969.