Further Studies on the Hypoglossal Nucleus in the Fowl

The delineation of the fowl's hypoglossal nucleus was determined by severing the hypoglossal nerve or its branches and observing retrograde degeneration. Birds were killed 7 or 10 days after surgery, the brains embedded in paraffin and cut at 10 μm. Transection of the hypoglossal nerve stem resulted in chromatolysis near the obex and no chromatolysis was found in the Nuclei cervicales. Severing of the laryngolingual branch led to degeneration phenomena near the obex nearly similar to the degeneration observed after severing of the hypoglossal nervestem. Cutting of the superior laryngeal branch caused a degeneration of cells caudal to the obex, and cutting of the syringeal branch resulted in chromatolysis in about the same area. The origin of the anastomosing branch between the first cervical and hypoglossal nerve was not found because no chromatolytic cells could be detected. Similarly the cutting of several upper cervical nerves did not lead to chromatolysis in the areas we investigated.