No. I.] SYMPATHETIC GANGLIA OF VERTEBRATES. 51 



branching, end in spiral fibers and pericellular plexuses. After 

 a longer or shorter course in the ganglion, the medullated 

 branches lose their medullary sheath, and, as non-medullated 

 fibers, also end in spiral and pericellular plexuses. 



3) The pericellular plexuses surround the cell bodies of the 

 sympathetic neurons, and are always intra-capsular. They 

 represent the ending of cerebro-spinal fibers in the ganglion. 



Sympathetic Ganglia of Reptilia. 



In the tortoise the sympathetic chain begins in the superior 

 cervical ganglion. The nerve connecting this ganglion with 

 the succeeding one runs in close relation to the pneumogastric 

 to about the middle of the neck, where it leaves the nerve, and, 

 passing outwards and backwards, reaches the middle cervical 

 ganglion ; in Chelydra serpentina, a ganglion nearly a centi- 

 meter in length. From this ganglion several branches are 

 given off, the largest of which passes toward the axilla and 

 ends in the inferior cervical ganglion. Crossing the brachial 

 plexus, the nerve which forms the continuation of the cord 

 ends in the stellate ganglion. The relative size of these three 

 ganglia differs in the several species studied ; also, to some 

 extent, in the same species. They are all, however, relatively 

 large, and for this reason were used almost exclusively. They 

 may be readily exposed by removing the plastron and pushing 

 aside the tissues of the neck. From the stellate ganglion two 

 filaments run back, one on each side of the subclavian artery, 

 to a small ganglion which lies on the first dorsal nerve. In 

 the succeeding dorsal segments are found small sympathetic 

 ganglia, resting on the spinal ganglia. The sympathetic cord 

 then runs back and becomes connected with sacral nerves. 

 The two chains may then be traced as a single nerve into the 

 tail, a number of small ganglia being found here. The account 

 of the sympathetic system of the tortoise has been taken, with 

 almost no alteration, from Martin and Moal's Handbook of 

 Vertebrate Dissection, Part I : How to Dissect a Chelonian. 

 Their description has reference more especially to the red- 

 bellied slider terrapin (Pseudemys rugosa); their description 



