KAMI COMMUNICANTES. 359 



branches to several (about four) ganglia. In this way the fibres contained in one 

 communicating branch may have a wide distribution in the sympathetic. 



White rami communicantes are not furnished by all the spinal nerves. 

 According to (laskell, by whose investigations the fundamental constitution of the 

 sympathetic and its relations to the cerebro-spinal nerves were first made clear, they 

 are found in the dog from the second dorsal to the second lumbar nerve inclusive ; 

 but Langley has shown that in the dog and cat white rami communicantes are 

 given off by the spinal nerves from the first dorsal to the fourth lumbar, and in the 

 rabbit from the first dorsal to the fifth lumbar inclusive. In man it is most 

 probable that they exist from the first dorsal to the first or second lumbar nerves, 

 perhaps also the third in some cases. The visceral branches of the second, third, 

 and fourth sacral nerves (pelvic splanchnic* of Gaskell) correspond to white 

 rami communicantes, although they do not join the sympathetic cord, but pass 

 directly to the prevertebral plexuses ; and in this group also are to be included the 

 visceral branches of the spinal accessory, vagus, glosso-pharyngeal, and facial nerves 

 (cervico-cranial rami viscerales, Gaskell), as well as the short root of the ciliary 

 ganglion from the third nerve. 



The medullated fibres passing into the sympathetic system are classified by Kolliker as 

 follows : 



() Sensory fibres which, when derived from spinal nerves, run in the posterior roots. 



(&) Vaso- and viscero-constrictors, proceeding from certain cranial (IX, X, XI) and 

 spinal nerves, mainly from the anterior roots of the latter, but possibly also from the 

 posterior roots. These fibres all end in ganglia of the sympathetic, and their action 

 is transmitted through pale fibres springing from the cells of the ganglia. 1 



(c) "Vaso- dilators and viscero-inhibitory nerves, given off from the above-mentioned 

 cranial nerves, and the anterior roots of spinal nerves. They are continued as medullated 

 fibres, not forming any connection with nerve-cells, to their respective organs. 



The existence of special trophic and secretory fibres in the sympathetic is as yet uncertain. 



Grey rami communicantes are found passing between the sympathetic cord and 

 all the spinal nerves. Their pale fibres arise wholly from the nerve-cells of the ganglia 

 of the sympathetic cord, and for the most part from the cells of the ganglion with 

 which the branch is connected. Pale fibres arising from the cells of one ganglion, 

 and running along the cord to leave by the grey ramus of the next ganglion, only 

 occur exceptionally (Langley). On entering the anterior primary division of 

 a spinal nerve, the fibres of the grey ramus are directed both peripherally and 

 centrally. Of those passing centrally, some go off in the posterior primary division 

 of the nerve, others enter the sheath of the nerve, the surrounding tissue in 

 the inter vertebral foramen, and the dura mater, running up to the latter in 

 the posterior root. In the whole of the anterior root, and in the intradural portion 

 of the posterior root, there are no pale fibres (Gaskell). The fibres passing distally 

 in the anterior and posterior primary divisions of the spinal nerves have been 

 shown, by experiments on animals, to supply vaso-motor nerves to the arteries of the 

 body-wall and limbs, pile-motor fibres to the muscles of the hairs, and secretory 

 fibres to the sweat-glands. 



Intermixed with the pale fibres in the grey rami communicantes there are also a 



1 To this group must also be added the pilo-motor nerves, which have been shown by Langley 

 and Sherrington to have a similar arrangement, as well as probably the motor nerves of the sphincter 

 muscle of the iris, which pass from the third nerve through the ciliary ganglion. The last r however, 

 present the peculiarity that the fibres of the short ciliary nerves arising from the cells of the ciliary 

 ganglion are medullated. 



It may also be observed here that doubt is thrown by Langley upon the universal validity of the rule 

 that fibres passing from the cerebro-spinal nerves to the sympathetic are medullated until they reach the 

 ganglion in which they end, while the fibres arising from the ganglion-cells are always non-medullated. 

 He thinks that spinal fibres sometimes lose their medulla some distance before reaching the cells 

 amongst which they end, and on the other hand that fibres proceeding from sympathetic ganglion-cells 

 may in some cases be medullated, like the short ciliary nerves. He also considers it probable that a 

 given fibre in the sympathetic is interrupted by a nerve-cell in one ganglion only. 



