1 16 Journal of Comparative Neurology. 



pathetic in any region, can be produced by stimulating the 

 spinal nerves in the vertebral canal, or by stimulating the cord 

 itself." I infer from from Langley's (78) account (from whom 

 this statement was taken) that Budge and Waller were the first 

 to discover this fact ; it has however since been repeatedly shown 

 by other investigators. 



Attention has already been drawn to the fact that the sym- 

 pathetic ganglia of the chain and the pre-vertebral ganglia are 

 connected with the spinal nerves by nerves known as the white 

 and grey rami communicantes. The efferent impulse excited, 

 on stimulating the cord or a spinal nerve within the vertebral 

 canal, must therefore reach the sympathetic, through one of 

 these communicating branches. On making sections of the 

 white and grey rami it may be seen that the white rami consist 

 almost entirely of medullated fibers, while the grey rami con- 

 tain a great many non.-medullated fibers. Gaskell (79) has 

 shown that the majority of the medullated nerves of the white 

 rami are unusually small, varying in size from 1.8 /j. to 2,7 fj , 

 He has further shown that in some of the anterior spinal roots 

 nerves of the same size and structure are to be found. To state 

 this in another form and to quote again from Gaskell, sections 

 of the several anterior spinal roots reveal these facts : — In sec- 

 tions of the anterior roots of the cervical nerves, hardened in 

 osmic acid, the great majority of the nerve fibers are large 

 medullated fibers, varying in size from 14.4 ^^ to 19 /< , a few 

 smaller fibers, not less than 3.6 ;/ in diameter, are also foynd. 

 The first thoracic anterior root has essentially the same struc- 

 ture. Beginning with the second thoracic nerve, all the anter- 

 ior roots to the third lumbar contain the small medullated fibers 

 above referred to, fibers of 1.8 // to 2.7 ^t in thickness, and 

 these can be traced into the white rami. It follows, then, that 

 only these spinal nerves have white rami. Langley (78) who 

 has examined the dog, cat and rabbit with reference to this 

 point, states that the uppermost white ramus is given off from 

 the first thoracic nerve, the lowermost probably from the 

 fourth lumbar. 



