THE STRUCTURE OF THE ROOTS, TRUNK AND 

 BRANCHES OF THE VAGUS NERVE 



M. R. CHASE AND S. W. RANSON 



The Anatomical Laboratory of the Northwestern University Medical School 



TWENTY FIGURES 



The work upon which this paper is based was begun by one of 

 us (Chase) on his own initiative. After the preparations were 

 all made, the observations collected in elaborate notes, and the 

 drawings completed, the wi'iting up of the paper fell to the lot 

 of the second author, who has, however, again gone over all the 

 material and writes from first-hand knowledge of the histological 

 details. 



It was formerly supposed that the cerebro-spinal nerves (ex- 

 clusive of the first cerebral) were composed ahnost entirely of 

 medullated fibers. But it has been demonstrated recently (Ran- 

 son '11, '12) that the spinal nerves contain even more non-med- 

 ullated than medullated fibers. Among the cerebral nerves two 

 have been studied in some detail in recent years. Weigner ('05) 

 found considerable numbers of non-medullated fibers in the 

 nervus intermedins. Molhant ('10) found groups of non-medul- 

 lated fibers in the vagus, which he thought were derived from the 

 sympathetic system. The Cajal silver technique was employed 

 by him to stain the axons, and his preparations were evidently 

 unsatisfactory. As a result, his account of the non-medullated 

 fibers in the vagus leaves much to be desired. He has, however, 

 given a good account of the medullated fibers in that nerve. 



It is not our purpose to present a review of the literature on 

 the vagus nerve, since this has been summarized recently by Mol- 

 hant. Such observations on the structure of the vagus as have 

 a direct bearing on those presented in this paper will be sum- 

 marized in another paragraph. 



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