RECAPITULATION OF THE NERVES. 271 



6. — The Abducens. 



The sixth nerve arises by two roots, each coming in 

 part from the abducens nucleus and in part from the fas- 

 ciculus longitudinals dorsalis. It is a pure somatic motor 

 nerve and has no connections with any other nerve. 



7. — The Trigeirmitis. 



In this nerve I have found but two components (Fig. 12). 

 The motor root is like that of the VII nerve. The 

 configuration of the oblongata is such at this point that it 

 emerges really dorsally of the sensory root. It enters the 

 r. mandibularis of the infra- orbital trunk and supplies the 

 mm. depressor operculi, levator arcus palatini, adductor 

 mandibulse, genio-hyoideus and intermandibularis. 



The general cutaneous root, after its entrance into the 

 brain, sends some fibres to the chief sensory trigeminal 

 nucleus and also makes up the whole of the pre-vagal 

 spinal V tract. From its ganglion (the Gasserian g.) 

 fibres enter the supra-orbital trunk (r. ophthalmicus 

 superficialis V), the infra- orbital trunk (r. maxillaris and 

 r. mandibularis V) and two twigs (only the more cephalic 

 one shown on Fig. 12, t. f. i) run back to enter the 

 truncus hyomandibularis for the skin of the lower part of 

 the operculum. In addition to these, a few fibres go out 

 with the radix longa of the ciliary ganglion which are 

 apparently general cutaneous, rather than sympathetic 

 and which I homologize with the r. ophthalmicus pro- 

 fundus trigemini. 



8. — The Trochlearis. 



This is, so far as known, a pure somatic motor nerve, 

 arising from its nucleus in the floor of the mesocoele and 

 doubtless also partly from the fasciculus longitudinalis 



