256 G. E. COGIIILL 



siderable luunbcr of fibers of this nerve attach themselves in a 

 cluster to the supraorbital lateral line primordium, to which the 

 course of the nerve has a definite relation. These branches from 

 the ophthalmic nerve have all been identified in silver impreg- 

 nations. 



The root fibers of the ophthalmic ganglion can be traced to the 

 brain and can be seen to enter the brain a little ventrad and 

 cephalad of the entrance of the root of the Gasserian ganglion 

 (figs. 51 to 53, R.oph). The intimate relation between the proxi- 

 mal portions of these two ganglia is shown in these figures. 



The Gasserian ganghon, like the ophthalmic, has become mOre 

 consolidated about the proximal portion of its root than in any 

 of the earlier stages. The infraorbital trunk has become still 

 more deeply embedded in the groove through the primordium 

 of the jaw muscles, across the entire lateral surface of which it 

 now descends to the vicinity of the balancer. To the balancer 

 it sends a nerve (fig. 4, c), which can be traced in both stained 

 preparations and silver impregnations, practically to the tip of 

 the organ where it has cutaneous distribution. About where 

 the main nerve leaves the groove it gives off the ramus maxillaris 

 (fig. 4, Mx.V) which now passes a considerable distance forward 

 under the eye. There is some evidence that this nerve arises 

 from cells that lie in the angle between the main projections of 

 the ophthalmic and Gasserian ganglia. Soon after giving off 

 the nerve to the balancer the ramus mandibularis divides into 

 two branches which turn cephalad and mesad ventrally of the 

 muscle primordia. These can be traced into close proximity 

 with the oral plate. In silver impregnations of embryos of this 

 age neurofibrils may be seen penetrating the skin along the 

 course of this nerve. The cutaneous distribution of the nerve, 

 however, is still less obvious than is that of the ophthalmic divi- 

 sion, excepting in the balancer, which is a highly innervated 

 organ at this stage. 



The root fibers of the Gasserian ganglion are shown in figures 

 51 to 54 as they enter the brain to form the more dorsal portion 

 of the ascending and descending trigeminal tracts. The extent 

 of these tracts is shown in figure 6 {Tr. asc.V,Tr.des.V). Silver 



