96 



Development of Occipital Nerves in Human Embryos 



continues the cell masses become broken up and separated into ganglionic 

 clumps. Instead of the uniform cellular crest seen in the occipital 

 region in Fig. 4 we find in Fig. 9 a chain of ganglia lying among the 

 rootlets of the ninth, tenth, and eleventh nerves. Just cephalad to the 

 first cervical ganglion, in Fig. 7, is a cell mass which may be regarded, 

 either as a fragment which has become separated off from the first cer- 

 vical ganglion, or what is more likely a persistent occipital ganglion 

 (precervical ganglion), such as is found by Froriep, 82, in the sheep. 



J^ccessory root gang. 



X root gang. 



Fig. 10. Reconstruction of peripheral nerves in five weeks human embryo, 13.8 mm. long, 

 Hertwig collection No. 67. Enlarged 16.7 diams. 



Embryos of Five to Seven Weeks. 



Hertwig Collection, No. 67 13.8 mm. 



Mall Collection, No. 14-L 14.0 mm. 



His Collection, Embryo FM 17.5 mm. 



(See Figs. 10, 11, 13 and Plate If.) 



At the end of the fifth week the ganglion crest is completely resolved 

 into a series of more or less segmental cell masses. The dorsal ridge, 

 which formed an intersegmental bridge across the tops of the spinal 

 ganglia, has disappeared. Simultaneously with the disappearance of this 



