THE SYMPATHETIC NERVOUS SYSTEM. 217 



with the methods here employed. The topographical re- 

 lations of the ganglia and the larger sympathetic nerves 

 are indicated upon Fig. 4, and will be here briefly re- 

 viewed, though they deviate but little from Belone and 

 other well-known examples, for which, compare the de- 

 scriptions of Stannius. 



My examination began on the left side at the level of 

 the fourth vertebra, where the sympathetic trunk of each 

 side lies close to the centrum, and the description will 

 proceed cephalad from this point. The fibres are small 

 but quite heavily myelinated. They are considerably 

 larger than the sympathetic fibres which go out with the 

 cranial nerves. Immediately caudad of the fourth spinal 

 ganglion, cells appear in the sympathetic cord. This 

 sympathetic ganglion is very small and ceases before the 

 spinal ganglion is reached. Now, instead of sending a r. 

 communicans to the ventral ramus of the spinal nerve in 

 the usual manner, the whole sympathetic trunk rises up 

 and becomes embedded in the ventral side of the spinal 

 ganglion and here additional sympathetic ganglion cells 

 are found. They can be distinguished from the cells of the 

 spinal ganglion by their smaller size. Sympathetic fibres 

 and a portion of the sympathetic ganglion run out into 

 the ventral ramus. A bundle of fibres passes also from 

 the sympathetic ganglion across the root of the ventral 

 ramus and back into the spinal ganglion. 



The sympathetic ganglion runs somewhat farther ceph- 

 alad than the spinal ganglion and from its tip the sympa- 

 thetic trunk again descends to its former position, laterally 

 of the centrum of the vertebra, in this case, however, 

 separated from the latter by the fleshy origin of the m. 

 retractor arcus branchii dorsalis, so that it lies between 

 this muscle and the head kidney close to the dorso-mesal 

 angle of the latter. 



