76 ALBERT KUNTZ 



from the middle part of the peripheral surface of the semilunar 

 ganglion by a broad base and converges gradually toward its 

 peripheral extremity. The mandibular, like the maxillary divi- 

 sion, is composed of loosely aggregated fiber-bundles. This divi- 

 sion may be traced from the ventral angle of the semilunar 

 ganglion anterio-ventrally into the mandibular region (fig. 2, 

 Mem). 



The semilunar ganglion, during the early stages of develop- 

 ment, is not sharply limited peripherally. Cells push out into 

 the proximal parts of the nerves arising from its periphery so 

 that in these regions it is quite impossible to determine the exact 

 limits of the ganglionic mass. Similar cells may be observed 

 associated with the fiber-bundles throughout the entire length 

 of the nerve-trunks. It is obvious, therefore, that cells of nerv- 

 ous origin advance peripherally from the semilunar ganglion 

 along the fibers of all three divisions of the trigeminal nerve. 



The motor root of the trigeminal nerve does not penetrate the 

 semilunar ganglion but advances diagonally ventrad and unites 

 with the sensory root of the mandibular division of the trigeminal 

 nerve. In embryos of the pig 10 to 11 mm. in length, the motor 

 root of the trigeminal nerve may be traced from the wall of the 

 rhombencephalon as a bundle of closely aggregated fibers (fig. 

 3, MR). The cells of the mantle layer at this point push out 

 across the marginal veil into the proximal part of the nerve-root 

 and many of them obviously migrate peripherally along its 

 growing fibers. In many sections through this region continuous 

 rows of medullary cells may be traced from the mantle layer 

 in the rhombencephalon into the proximal part of this motor 

 nerve-root (fig. 3, MC). Similar cells may be observed all along 

 the fibers of this motor root as well as along the mandibular 

 nerve peripheral to the point of union of the sensory and the 

 motor roots. Bej^ond this point the cells of medullary and of 

 ganglionic origin can not be distinguished from each other. It is 

 probable, however, that cells from both these sources advance 

 peripherally along the fibers of the mandibular nerve. 



