508 ANATOMICAL TECRNOLOGY. 



commonly described as a single nerve, it really consists of two, the larger being sensory 

 (Radix sensoria) and the smaller motor (Radix motoria). It thus conforms to a myelonal 

 nerve, excepting that the ectal origins of the two roots are closely associated. 



The sensory root is a large, slightly flattened band which lies across the pons just 

 where it is contracted to form the medipedunculus. When lifted from the pons, it is 

 found to have its ectal origin either just caudad of it or from its surface close to the caudal 

 border. 



In the senior author's paper {14;, 548), the nerve is simply said to arise caudad of the 

 pons. This statement was questioned in the Am. Jour, of Neurology, etc. (I, 103) ; a 

 reexamination of several preparations shows the existence of the variation above indi- 

 cated, and a qualification has been published (Wilder, 24:). 



In man the ectal origin is through the pons nearer the cephalic than the caudal mar- 

 gin. In part, at least, the difference is due to the greater caudal extension of the human 

 pons (§ 1161). 



At the cephalic border of the pons the root presents a large flattened ganglion (Qng. 

 Gasseri) and then separates into three divisions — the ophthalmic, maxillary and mandibu- 

 lar. Of these, the first is the most mesal in position and the smallest, but with it are asso- 

 ciated the oculomotorius, trochlearis and abducens, all emerging together from the Fm. 

 lacerum anterius. 



The maxillary division is intermediate and escapes by the Fm. rotundum. The man- 

 dibular division is lateral, is joined by the Radix motoria and emerges by the Fm. ovale. 



The distribution is stated upon the Table (§ 1392), and corresponds in the main with 

 the three regions of the face; some filaments also supply the dura. 



The motor root (Radix motoria) is much smaller than the sensory and not easily recog- 

 nized. Upon a fresh brain it may be seen as a narrow, light band crossing the sensory 

 root and the ganglion from the mesal side of the former, to attach itself to the mandibular 

 division. Upon an alcoholic brain, a dull tracer may be used to isolate it in the middle of 

 its course and follow it to its origin mesad and slightly cephalad of that of the sensory 

 root. We have not ascertained whether, as in man, it is separated therefrom by a few 

 fibers of the pons or of the trapezium. 



In man the motor root is distributed to the muscles concerned in mastication (Dalton, 

 A, 464). 



§ 1385. Nervus abducens, S. abd., the abducens nerve.— Fig. 116 ; PI. II, Fig. 3. 

 Gray, A, 641 ; Quain, A, I, 519, 



A ribbon-shaped nerve, arising by three or four funiculi from the trapezium just laterad 

 of the pyramis. The attachment is very feeble and the nerve is apt to be torn aS with 

 the pia. It associates itself with the ophthalmic division of the trigeminus and emerges 

 therewith by the Fm. lacerum anterius to be distributed to the MM. choanoidei and the 

 rectus lateralis (" externus "). 



§ 1386. (VII) Nervus facialis, N. /., the facial nerve or " portio dura." — Fig. 116 : 

 PI. II, Fig. 3. Gray, A, 642 ; Quain, A, I, 548. 



In some respects this is the motor counterpart of the trigeminus, being distributed to 

 most of the muscles of the face and head, excepting the muscles of mastication. It is 

 small as compared with the trigeminus, just caudad of which it arises from the latero- 

 cephalic angle of the trapezium. It traverses the ental auditory foramen, the Aquseductus 

 Fallopii and the stylo-mastoid foramen (§ 506). 



§ 1387. (VIII) Nervus auditorius, N. an., the auditory or acoustic nerve or portio 

 mollis.— Fig. 110, 116 ; PI. II, Fig. 3. Gray. A, 639 ; Quain, A, I, 548. 



This is commonly grouped with the olfactory and optic nerves as a nerve of special 



