378 NERVOUS SYSTEM. 



above, but below they assemble into larger and more distinct 

 fasciculi, which are afterwards arranged into three principal 

 trunks, departing from the cranium through different foramina ; 

 to wit: through the sphenoidal foramen, the foramen rotundum, 

 and the foramen ovale. 



J. F. Meckel asserts that the filaments of the plexus above the 

 ganglion, for the most part terminate in a gutter formed in the 

 superior margin of the ganglion, and that there are but very 

 few of them which can be traced into the trunks below. The 

 trunks below, consequently, arise from the circumference of the 

 ganglion. 



The two smaller roots of the nervus trigeminus proceed out 

 of the tuber annulare at different points, from that of the large 

 root, and each one has its appropriate fissure for that purpose. 

 One, from its situation, is, as stated, called Anterior, and the 

 other Posterior. Each may be traced into the posterior chord 

 of the medulla oblongata, but not so far as the large middle 

 root, and is formed by several fasciculi of medullary fibres. 

 The anterior and posterior root, after going separately for six 

 or eight lines, unite to form a single chord.* This chord does 

 not merge itself in the semi-lunar ganglion, but continues 

 distinct from it,-f with the exception of sending off to it a few 

 fasciculi ; and it sometimes has its own distinct canal, and aper- 

 ture in the dura mater for passing through it; it afterwards gets 

 from the cranium through the foramen ovale, and is distributed 

 to some of the muscles of mastication, as the temporal and buc- 

 cinator. 



The general distribution of the fifth pair of nerves, or the 

 trigeminus, is to the orbit, to the face, and to the tongue. 



The Motor Externus Oculi, or Sixth Pair of Nerves (Par 

 Sextum) arises from the base or upper extremity of the corpus 

 pyramidale, under the posterior margin of the tuber annulare 

 or Pons: when the latter is broader than usual, some of the 

 fibres seem to come from it; but the appearance is deceptious, 

 as they only penetrate it. The fibres are assembled into two 



* These two constitute what is called the raotory part of the fifth nerve. Mr 

 Solly considers it to arise from the valve of the brain near its root. p. 249. 

 f- In this respect the fifth pair resembles one of the spinal nerves. 



