[The ultrastructure of the nucleus of the solitary tract of the sheep and goat].

The sensory nucleus of the IXth and Xth cranial nerve in sheep and goat takes a position in the middle of the elongated medulla forming a bilateral symmetric cell column. Neighbouring the canalis centralis dorsolaterally the caudal segments of both nuclei are connected in the raphe region by a subnucleus commissuralis. The solitary tract defines the nucleus in its lateral extension. The area postrema limits the rostral pole from the surface. Two distinct types of neurones are observed in the light and electron microscope. The small neurones show a paucity of organelles and an invaginated nucleus. According to their synaptic density three variations of small neurones could be distinguished. The large neurones are more compact in their cytoplasmic organisation. According to their size and morphology of vesicles five types of synaptic boutons could be differentiated. Most of the profile of the perikarya is surrounded by astrocytes and their extensions.