EOOTS, TRUNK, BRANCHES OF VAGUS NERVE 35 



the vagus in the rabbit, was able to demonstrate the presence 

 of bundles of non-medullated nerve fibers, which correspond to 

 clear areas in preparations stained by osmic. He believes that 

 these fibers have their origin in the sympathetic system. 



Ranvier ('89) found non-medullated fibers in the vagus; but 

 he figured them as branching and forming plexuses. He prob- 

 ably teased out groups of non-medullated fibers. 



STRUCTURE OF THE ROOTS OF THE VAGUS AND ACCESSORY NERVES 



Osmic acid preparations. As was stated above, the rootlets of 

 the glossopharyngeal, vagus and bulbar portion of the accessory 

 nerve arise in a continuous series from the dorso-lateral sulcus 

 of the medulla. The spinal portion of the accessory arises from 

 the cervical segments of the spinal cord and is joined by the bul- 

 bar rootlets. A study of serial sections of the roots of the vagus 

 and accessory nerves, which were removed and fixed with a 

 small piece of the medulla attached, shows the rootlets grouped 

 as in figures 1, 2 and 3. Two complete series of sections were 

 studied. One of these was stained with osmic acid and the other 

 by the pyi'idine-silver technique. In this way the structure of 

 each set of rootlets was determined. 



We will examine first the series stained with osmic acid. At 

 the lower part of figure 2 is seen the large spinal root of the ac- 

 cessory nerve. This has been joined by some of the bulbar root- 

 lets (6). The spinal root is composed almost entirely of large 

 medullated fibers with a very few small ones. The fibers are 

 evenly spaced, leaving no clear areas like those seen in some of 

 the rootlets of the vagus. The bulbar portion of the accessory 

 is composed of large and small fibers, the latter predominating. 

 These rootlets are also free from the clear areas seen in some of 

 the radicals of the vagus. Figure 4 is a high-power drawing 

 from one of these bulbar rootlets of the accessory. 



The roots of the vagus nerve (fig. 2, a) come off from the me- 

 dulla as a compact group. There may be many fine radicals or 

 one large root and a number of small ones. There are two very 

 different kinds of vagus rootlets. One group. Type I, represented 



