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The projection from the chick optic tectum to the nucleus rotundus was investigated by iontophoresis of the anterograde tracer Phaseolus vulgaris lectin (PHA-L) into the optic tectum and by Golgi impregnation. PHA-L labelled fibres were observed within the ipsilateral nucleus rotundus and to course through the supraoptic decussation to the contralateral nucleus rotundus. They appeared similar to fibres evident in Golgi impregnated material. Before reaching the nucleus rotundus, PHA-L labelled fibres gave off short terminal branches in the caudoventral thalamic nucleus. Within the ipsilateral nucleus rotundus, the labelled fibres formed an extensive fibre net with a dense core and a less dense periphery. PHA-L labelled fibres in the contralateral nucleus rotundus exhibited a qualitatively similar but sparser distribution. There appeared to be a topographic representation of the optic tectum within the nucleus rotundus. Electron microscopy revealed that PHA-L labelled tectal fibres established asymmetric synapses with principal neurons in the nucleus rotundus.

The neuronal structure of the amygdaloid complex was studied in cat with Golgi-Kopsch perfusion technique. Four types of neurons were distinguished: the projective neurons (longaxonal), with the structure being different in the area anterior, corticomedial and basolateral parts of amygdala; the Golgi IIa neurons (shortaxonal), observed in all nuclei of the amygdala; the Golgi IIb neurons (mediumaxonal), mostly observed in the dorsal part of the lateral nucleus; the Golgi IIc, neuroglioform type of neurons with short but very profusely arborized axons, present exclusively in the ventrolateral area of the basolateral part of amygdala. In addition, some afferent fibers have been visualized in the basolateral part of amygdaloid complex.