Propriobulbar fibre connections to the trigeminal, facial and hypoglossal motor nuclei. I. An anterograde degeneration study in the cat.

The local bulbar connections to the V, VII and XII motor nuclei in the cat have been studied by means of the anterograde fibre degeneration technique in combination with the Fink-Heimer silver impregnation procedure. For this purpose electrolytic lesions were made mainly in the reticular formation of the medulla oblongata and the pons. For control purposes also, extrabulbar lesions were made in the cervical cord and the upper brain-stem and in addition, primary afferent fibres were interrupted by section of the upper cervical and trigeminal roots. The findings indicated the existence of a lateral and a medial propriobulbar fibre system, the former of which projects to the motor nuclei mainly ipsilaterally, while the latter tends to project bilaterally. Since the cells of origin of the propriobulbar fibre systems are difficult to determine by means of the anterograde degeneration technique these systems have also been investigated by means of the labelled amino-acid tracing technique. The findings thus obtained are reported in the adjoining paper.