320 H. W. NORMS AND SALLY P. HUGHES 



THE TRIGEMINAL NERVE 



1. The roots and ganglia of the trigeminal complex 



According to Landacre ('16), the roots of the trigeminal nerve 

 in 22-mm. embryos of Squalus acanthias are in two groups: (I) 

 an anterior portio minor of three roots: 1) sensory fibers by which 

 the profundus ganglion connects with the tractus spinalis tri- 

 gemini; 2) motor fibers; 3) sensory fibers, presumably belonging 

 to the maxillomandibular division of the fifth nerve; (II) a pos- 

 terior portio major, consisting of sensory fibers entering the 

 spinal V tract. At the stage examined by the writers there are 

 found in the portio minor four or five rootlets: 1) an anterior 

 dorsal rootlet of motor fibers, with which are possibly associated 

 sensory elements; 2) motor fibers; 3) fibers ending in the spinal 



V tract, and presumably sensory; 4 and 5) motor fibers (figs. 12 

 to 14, 21, 22, and 25 to 30, pmn.V, 1-5). The portio major con- 

 sists of a large number of sensory rootlets entering the spinal V 

 tract, with which are mingled a small number of motor fibers 

 (figs. 12 to 14, 21, 22, 29, 30, and 32, pmj.V). 



That the first rootlet of the portio minor is largely motor is 

 beyond question, but its exact composition the writers have found 

 well nigh impossible to determine. That fibers from the pro- 

 fundus ganglion enter the brain through this first rootlet seems 

 possible; they appear to do so. In fact, the relations in the gas- 

 serian ganglion would justify the supposition that all the rootlets 

 of the portio minor contain sensory elements, but their course 

 in the brain does not warrant such a conclusion. The first 

 rootlet passes directly into the anterior continuation of the spinal 



V tract, where it divides into two parts, one continuing on di- 

 rectly into the lateral motor column, the other turning abruptly 

 anteriorly and becoming the radix mesencephalica V. Appear- 

 ances permit the assumption that some fibers of this first rootlet 

 may end in the spinal V tract. The second rootlet seems to be 

 exclusively motor. It passes through the spinal V tract, but 

 shows no indications of giving fibers to it. The third rootlet is 

 very small. It arises immediately posterior to the second root- 

 let, and in some specimens cannot be recognized, probably being 



