58 bulletin: museum of comparative zoology. 



extension of the sympathetic ramus is cephalad in the infraorbital 

 nerve. This is shown by the character of the cross section of the 

 nerve and by the direction of the fibers in the gangUon. The further 

 anastomoses of nerves V and VII to form the infraorbital plexus offers 

 opportunity for the wide distribution of this system throughout the 

 head region. Practically every point of juncture in this complex is 

 the seat of a larger or smaller group of sNTupathetic ganglion cells 

 (Plate 2, fig. 4, cl. gn.sy.). Except in the case of the infraorbital 

 ganglion, none of those on the maxillary nerve is large enough to have 

 been discovered by gross dissection without the aid of mounted pre- 

 parations of dissected parts, a method which apparently has not been 

 used by my predecessors. It is noticeable that, after the nerve is 

 free from visceral connection, as in the ramus alveolaris superior, no 

 more ganglia are found. 



III. Ramus mandibularis (nid.). This is the largest of the tri- 

 geminal branches, but, unlike the other two, it is not wholly afferent 

 in its composition. It includes a certain number of motor components, 

 which are given off to the mylo-hyoideus muscle. The mandibular 

 ramus leaves the portio major of the Gasserian ganglion from its 

 ventro-lateral side (Plate 3, figs. 6, 7), being covered dorsally by the 

 ramus maxillaris. Its course to the lower jaw lies between the mm. 

 pterygoideus and pterygo-sphenoidalis posterior. It crosses dorsal 

 (lateral) to the pterygoquadrate process just behind the insertion of 

 the m. pterygo-parietalis, passing through the deeper part of the 

 pterygoideus to reach the median side of the mandible (Plates 5, 6, 

 figs. 15-17). x\s it approaches the mandible two rami are given off 

 together to be distributed to skin and muscle of this region. The 

 continuation of the main nerve is known as the ramus alveolaris 

 inferior {ah. if.). It still contains a few motor fibers for the inner- 

 vation of the anterior part of the m. mylo-hyoideus. 



Ill, 1. The two branches above mentioned are given off from the 

 main ramus at the point where the latter makes a turn cephalad to 

 enter the mandible. They might be considered one branch which 

 immediately divides into a posterior and an anterior ramus. The 

 posterior ramus (md.^) turns back (Plates 2, 3, figs. 5, 6) and crosses 

 Meckel's cartilage dorsally, reaching the lateral side of the mandible 

 (Plate 6, fig. 16) through a foramen between the dentary and angu- 

 lare bones. It passes through the superficial throat muscles to the 

 mylo-hyoideus muscle, a very small sensory twig passing on to the 

 skin. Most of the fibers are motor, innervating a part of the mylo- 

 hyoideus muscle (Fig. J). 



