The myelinated fibers in the aortic nerve of the swine

The aortic nerves of 24 Chester White swine were identified electrophysiologically by the synchronization of the recorded action potentials with the cardiac cycle; and the occurrence of the maximum firing rates observed on the oscilloscope during systole. The aortic nerve, thus identified, was traced to the aortic arch in two preparations. The left aortic nerve was a separate bundle in 15 of 24 (62.5%) swine investigated. In the remaining 37.5% of the swine the nerve was dissected from within the vagus after identification at the level of the nodose ganglion. At this level the aortic nerve leaves the ganglion with the superior laryngeal nerve, runs caudomedially with it a short distance, then loops back laterally into the vagus to run caudally to the arch of the aorta. An aortic nerve was not observed in the right vagus nor in the sympathetic trunk of either side. The myelinated fibers counted from six aortic nerves were less than 10 μ in diameter with the majority in the 2–6 μ range, and averaged 542 in number.