90 bulletin: museum of comparative zoology. 



region. The second {XII ^) goes to the small slip of muscle described 

 as the cerato-mandibularis 3 (Plate 6, figs. 16-19, kcr-md.^) sending 

 also a few fibers to the same muscle that receives the first twig. 

 Some distance cephalad a third ramus (XII ^) is given off, which in- 

 nervates this first muscle, the most of the bundle, however, passing 

 far forward to reach the portion described as cerato-mandibularis 2 

 (Plate 2, fig. 5; Plates 4, 5, figs. 9-12, ker-md.^). Just anterior to 

 this several small branches (Plate 2, fig. 5, XII ■*) supply the posterior 

 portion of the genioglossus. 



It is noticeable that all these small rami to the more superficial 

 tongue muscles draw off from XII the largest and most strongly 

 medullated of its fibers, although not exclusively fibers of this kind. 

 There is no further distribution of fibers of XII from the main trunk, 

 which now may be said to supply the tongue proper through the three 

 main divisions referred to above. For convenience in description 

 these will be described as median, intermediate and lateral rami. 



Ramus lingualis medialis XII (big. m. XII). This ramus crosses 

 the ventral side of the main longitudinal tongue muscle, genioglossus, 

 to reach the median edge of this muscle. Here, on either side of the 

 glossohyal (gls-hy.) and underlying the larynx, begins a mass of muscle 

 composed of short vertical fibers (Plate 4, fig. 11, lug. vrt.). This forms 

 a continuous vertical muscle surrounding the glossohyal as far forward 

 as its anterior end, which is well toward the tip of the tongue. The 

 median ramus of XII runs the length of this muscle supplying it on the 

 way (Plate 2, fig. 5). As the vertical fibers gradually run out, this 

 nerve also dwindles. The fibers innervating this muscle are less 

 heavily medullated than those of the small rami previously described. 



Ramus Imgiialis intermedius XII (Plate 2, fig. 5, Ing. i'm. XII). 

 This ramus is a little larger than the median one and the fibers are 

 larger and more heavily myelinated. It runs cephalad first on the sur- 

 face of the muscle genioglossus then within that muscle. This ramus 

 appears to supply the genioglossus exclusively. Its course may be 

 followed in the drawings of cross sections (Plate 4, 5, figs. 9-12). 



Ramus lingualis lateralis XII (Ing. I. XII). This is the largest 

 division of XII and the one which forms the anastomoses with the 

 lingual branch of V (Plate 2, fig. 5, lug. V) ; before this union, however, 

 it divides into two rami of about ecjual size (Ing. I. XII ^ and Ing. I. 

 XII -) giving off just proximal to the division a small ramus (XII *) 

 supplying the longitudinal tongue muscles. Of the two main divisions 

 one is distributed at once in a series of branches to the transverse 

 musculature (Plate 4, figs. 10, 11, lug. t.) on the upper surface of the 

 tongue, the nerve fibers reaching this muscle at its extreme lateral 



