238 ALBERT KUNTZ 



The sixth sympathetic ganglion arises in contact with the 

 mesial aspect of the first spinal nerve and the jugular ganglion 

 of the vagus nerve. In transverse sections of embryos of Opsanus 

 6 mm. in length, the anlage of this ganglion may be observed 

 stretching ventro-mesially from the first spinal nerve just periph- 

 eral to. the spinal ganghon (fig. 2, sy6). This ganglionic anlage 

 appears, in tran verse section, as an elliptical aggregate of cells 

 removed by a short interval from the spinal nerve, but connected 

 with the latter by a broad cellular tract. Medullary cells may be 

 traced, at this stage, from the mantle layer in the neural tube 

 across the marginal veil and the external limiting membrane 

 into the ventral root of the first spinal nerve (fig. 2, vr spl) . As 

 these cells advance peripherally along the fibers of the ventral 

 nerve-root some of them mingle with the cells in the distal por- 

 tion of the spinal ganglion; most of them, however, may be traced 

 along the ventro-mesial aspect of the spinal ganglion into the path 

 of the spinal nerve. The spinal ganglion is not sharply limited 

 peripherally, but cells become separated from it and advance 

 farther peripherally along the fibers of the dorsal root of the spinal 

 nerve. Some of these cells, doubtless, deviate from the path of 

 the spinal nerve and enter the anlage of the sympathetic ganglion. 

 It is probable that cells which wajider out from the neural tube 

 along the fibers of the ventral nerve-root also enter the anlage 

 of this ganglion. This sympathetic ganglion, therefore, probably 

 receives cells from both the neural tube and the first spinal 

 ganglion. 



The anlage of the sixth sympathetic ganglion may be traced 

 cephalad from the level of the first spinal nerve as a somewhat 

 flattened aggregate of cells to a level somewhat anterior to the 

 posterior margin of the ganglionic complex of the vagus nerve. 

 In transverse sections at this level, a broad band of cells may be 

 traced from the jugular ganglion into the sixth sympathetic 

 ganglion (fig. 3, sy 6). Cells, doubtless, advance from the jugular 

 ganglion along this tract into the sympathetic anlage. The sixth 

 sympathetic ganglion is, therefore, genetically related to both the 

 first spinal and the X cranial nerves. 



