No. I.] SYMPATHETIC GANGLIA OF VERTEBRATES. 79 



nerve within the vertebral canal. This, as is now well known, and 

 first clearly shown by Gaskell (50), is explained by the fact that 

 certain small medullated fibers, which leave the cord through 

 the anterior roots of certain spinal nerves — first dorsal to the 

 third or fourth lumbar inclusive — reach the sympathetic ganglia 

 through the white rami communicantes. These fibers end, not 

 only in the ganglia of the chain, but also may be traced into 

 the pre-vertebral and even the peripheral ganglia, as the follow- 

 ing statement taken from Gaskell's account may show : 



" The white rami communicantes are formed by an outflow 

 of medullated fibers from both the anterior and posterior roots 

 of the spinal nerves between the second thoracic and second 

 lumbar inclusive, which medullated fibers pass not alone into 

 their metameric sympathetic lateral ganglia, but also form three 

 main streams, upwards into the cervical ganglia, downwards into 

 the lumbar and sacral ganglia, and outwards into the collateral 

 (pre-vertebral) ganglia. The white rami communicantes alone 

 constitute the rami viscerales of the morphologist. The outflow 

 of visceral nerves from the central nervous system into the so- 

 called sympathetic system takes place by their means alone." 



That these small medullated fibers are the fibers which, in 

 all vertebrates studied, end in the sympathetic ganglia in peri- 

 cellular plexuses, may now be assumed with much certainty; and 

 this for two main reasons : 



a) Medullated fibers have been traced from the white rami 

 into the sympathetic ganglia, or from some nerve root into the 

 peripheral ganglia, and have been seen to end in pericellular 

 plexuses, as repeatedly stated. 



b) The researches of Langley (51), Anderson, and Dickinson 

 have taught us that in nicotin we have a drug which shows 

 most clearly that the action of such fibers is interrupted in the 

 sympathetic ganglia ; that the sympathetic effects which may 

 be obtained on stimulating a cerebro-spinal nerve, containing 

 the small medullated fibers first described by Gaskell, or a 

 white ramus made up of such fibers, cannot be obtained if a 

 solution of nicotin of proper strength be injected into the circu- 

 lation of the animal or be applied to the sympathetic ganglia 

 with which such fibers are connected. 



