300 G. E. COGHILL 



the afferent system, but it is important to observe here that this 

 paper describes specific instances of migration of cells masses in 

 the form of several of the cranial ganglia. The clearest cases of 

 this are the Gasserian and profundus ganglia, particularly the 

 latter. This movement of the ganglia along the root towards 

 the brain deserves more exhaustive and specific study, but some 

 factors in the problem may be definitely stated. The ganglion 

 of the ophthalmicus profundus V, for instance, in the earlier 

 period is anchored to the skin far out over the eye. While this 

 anchorage is intact root fibers make their connection with the 

 brain. In embryos of the early flexure stage these fibers have 

 established a firm anchorage to the brain by the bifurcation of 

 the root beneath the external limiting membrane, and now their 

 hold upon the skin is lost. Immediately a movement of the 

 ganglion begins which finally carries it snugly up against the 

 brain immediately around the entrance of the root (figs. 51 to 

 54).. During this migration there are no apparent extrinsic 

 mechanical factors introduced. A comparison of figures 1 and 

 2 shows that the migration has begun before the ganglion comes 

 into contact with the eye, and comparison of figures 76 and 78 

 shows that after the ganglion comes in contact with the most 

 dorsal portion of the eye it moves caudad over the surface of the 

 eye — a median section through the eye in figure 78 showing 

 only the tip of the ganglion while a similar section in figure 76 

 shows the massive portion of the ganglion. The ganglion moves 

 caudad, therefore, with reference to the eye as well as with 

 reference to the brain and auditory vesicle. There must be, 

 then, some intrinsic factor involved in this movement. 



As such a factor the root fibers with their firm achorage 

 within the brain immediately suggest themselves (fig. 22). As 

 has been described above, these fibers are growing very rapidly 

 caudad towards the chief motor centers in the lower portion of 

 the medulla oblongata and the upper portion of the spinal cord. 

 This growth may be regarded not simply as an increase in mass 

 but as an active stretching out of the whole fiber in an amoeboid 

 fashion after the manner of the movements of nerve cells grow- 

 ing in vitro as Harrison ('10, '11) has described them. In other 



