Research of the central beginnings and endings of the accessory nerve (N. accessorius Willisii)

Starting at the end of the 16th century (Volcherus Goiter - 1573) and up to our time, about sixty authors studied the accessory nerve, partly dedicating special work to it, partly giving their views on the course and ending of this nerve in the textbooks of anatomy and histology published by them. Such persistence in the study of the accessory nerve is explained by the duality of its central beginnings and endings, that is, its origin both from the oblong and from the spinal cord. Already with a rough anatomical examination, it is clear that part of the roots emerging from the lower part of the medulla oblongata, not reaching the foramen jugulare of the skull, joins the nerve trunk, which runs along the lateral surface of the spinal cord and is formed by the connection of the roots emerging from the lateral brain. This common nerve trunk, emerging from the cranial cavity through the foram. jugulare and consisting of N. accessorius vagi and N. accessorius spinalis, received the name N. accessorius Willissi, named after Thomas’a Willis’a (1682) who described it. After exiting the foramen jugulare, the nerve gives a thin v-point (ramus internus — according to Heihendain’y) to the plexus ganglioformis n. vagi, and another, thick branch, is sent to the muscles (m. sternocleido-mastoideus). Thus, without the help of a microscope, a close connection between the XI and X pairs of cranial nerves is visible. To this, it must be added that the roots of the XI nerve, emerging from the lower sections of the medulla oblongata, produce the impression of the lower roots of the X nerve, and only their entry into the common trunk of the accessory nerve forces them to be referred to it. Heidenhain, using a physiological method, proved the connection between the accessory nerve and the vagus: he pulled out the accessory nerve in rabbits on the neck and after a few days after the operation did not receive the usual slowing of heartbeats with irritation of the vagus nerve; From this, the author concludes that the retarding heartbeat fibers of the vagus nerve receive an additional one through the ramus internus. Further, the author comes to the conclusion that the fibers of the accessory nerve, which delay the heartbeat, originate from the medulla oblongata. To confirm this view, Heidenhain cites experiments in which he, during artificial respiration of an animal, provided a cut of the medulla oblongata at the apex of the pen (calamus scriptorius) and below; with a slowdown of artificial respiration in the first case, a slowdown of the heartbeat was obtained, and in the second it did not work. Finally, in rabbits, after the accessory nerve was torn out, the laryngeal paralysis was as clearly expressed as after the X nerve was cut; food got into the respiratory tract, and the animals died from pneumonia, which usually began with the upper lobes).