242 ALBERT KUNTZ 



smaller size of the cells composing it. In embryos 12 to 14 mm. 

 in length, many of the cells in the Gasserian ganglion have already 

 become differentiated into neuroblasts. The difference in the size 

 of the two types of cells has now become so marked that the sym- 

 pathetic ganglion may be readily recognized (fig. S, sy 1). It is 

 now differentiated into a median and a lateral lobe. This ganglion 

 obviously arises directly from the Gasserian ganglion and remains 

 intimately associated with the latter. 



Ciliary ganglion 



The anlage of the ciliary ganglion arises about the time of 

 hatching as an accumulation of cells in the path of the oculo- 

 motor nerve. In embryos 6 mm. in length, the oculomotor nerve 

 may be traced from its origin in the wall of the mesencephalon 

 to the anlage of the ciliary ganglion in one or two transverse sec- 

 tions. Emerging from the w^all of the mesencephalon it advances 

 laterally for a short distance and then makes a sharp curve ven- 

 trally. The anlage of the ciliary ganglion now lies lateral to the 

 growing nerve and in immediate contact with it (fig. 9, cil g). 

 At the point where the sharp curve occurs, there is a slight ac- 

 cumulation of cells obviously of nervous origin. As development 

 advances, this accumulation of cells gradually decreases in size 

 until it probably disappears. Throughout the entire length of 

 the nerve-trunk its fibers are accompanied by numerous cells 

 of nervous origin. These cells, doubtless, have their origin in 

 the wall of the mesencephalon and advance peripherally along 

 the fibers of the nerve-root. While medullary cells may rarely 

 be observed in contact with or crossing the external limiting 

 membrane, there can be no doubt that such cells wander out into 

 the root of the oculomotor nerve in considerable numbers. Cells 

 push out from the oculomotor nidulus in a cone-shaped mass 

 into the root of the nerve as it traverses the marginal veil and 

 similar cells are always present in considerable numbers in the 

 nerve-root just ouside the external limiting membrane as well as 

 in the path of the nerve-trunk. These cells are identical in appear- 

 ance with the cells in the anlage of the ciliary ganglion. 



