Comparative study of the dorsal motor nucleus of the vagus nerve.

Quantitative studies were made of cells in the dorsal motor nucleus of the vagus nerve in the horse, dog, cat, pig, sheep, goat, and calf. This nucleus was larger in ruminants than in nonruminants. Some cells in all parts of the nucleus supplied visceral structures in the head, cervical, thoracic, and abdominal regions; however, a definite topographic localization did exist within the nucleus. Eighty percent of the cells which supplied the abdominal viscera were in the rostral and rostral-middle regions. The cells which supplied the thoracic viscera were distributed almost equally within the rostral three-quarters of the nucleus. Seventy-three percent of the cells which supplied viscera in the head and neck regions were in the caudal-half of the nucleus. The rostral region of the nucleus was much larger in ruminants than in nonruminants. It is proposed that cells in the rostral region of the nucleus supply the highly developed rumen and reticulum.