358 



THE SYMPATHEI1C NERVES. 



interrupted in any of the ganglia above mentioned. From the cells of the ganglia 

 other fibres, in great part it' not entirely non-medullated, arise. These are the 

 proper sympathetic fibres. They run partly in the grey rami communicantes to the 

 spinal nerves, partly in the rami efferentes and the offsets of the collateral and 

 terminal ganglia to their ultimate distribution. 



The great gangliated cords (trunci sympathies) are two in number, and 

 each consists of a series of ganglia (ganglia trunci sympat/iici), united by short 

 intervening cords, sometimes double. These gangliated cords are placed symmetri- 

 cally, partly in front, and partly on the side, of the vertebral column, extending 

 from the base of the skull to the coccyx. Superiorly they are connected with 



Fig. 229. SCHEME OF THE SYMPATHETIC CORD AND ITS CONNECTION* 



WITH THE SPINAL NERVES. (Gr. D. T. ) 



Meclullated fibres passing into and through the sympathetic cord 

 are represented by continuous lines, pale fibres arising from the 

 sympathetic ganglia by dotted lines. 



plexuses which enter the cranial cavity, while interiorly 

 they converge on the sacrum, and terminate in a loop on 

 the coccyx. The several portions of the cords are dis- 

 tinguished as cervical, dorsal or thoracic, lumbar, and 

 sacral, and in each of these parts the ganglia are equal 

 in number, or nearly so, to the vertebrae against which 

 they lie, except in the neck, where there are only three. 



Connection of the gangliated cords with the 

 cerebro-spinal system. The ganglia are severally 

 connected with the anterior primary divisions of the 

 spinal nerves in their neighbourhood by short filaments 

 called rami communicantes, which are of two kinds, white 

 and grey, the former consisting mainly of medullated 

 fibres, and the latter of pale fibres. In some cases these 

 are separate branches ; in others they are united in one 

 cord, which then consists of a white and a grey part. 

 As a rule, the communicating branches join the ganglia 

 of the sympathetic trunk, but sometimes they unite with 

 the part of the cord connecting adjacent ganglia. 



White rami communicantes are composed, as 

 stated above, mainly of very fine medullated fibres passing 

 from the spinal nerves to the sympathetic cord. The 

 fibres proceed from both roots of the spinal nerves, but 

 to a greater extent from the anterior. It is probable that 

 the fibres derived from the posterior roots are for the 

 most part afferent, but it has been shown by v. Lenhossek and others in the chick 

 that the posterior roots also contain fibres which spring from cells of the spinal cord, 

 and are believed to enter the sympathetic (Kolliker). These fibres have, however, 

 as yet not been observed in mammals, and Sherrington in the cat and monkey failed 

 to find evidence of any fibres in the posterior roots arising from cells of the spinal 

 cord. Some of the medullated fibres are continued over the ganglia of the cord to 

 enter the efferent branches ; others end in the ganglia, often ascending or descending 

 for a considerable distance in the cord to reach ganglia at a higher or lower level 

 than that of the communicating branch by which they pass to the sympathetic. 

 The individual fibres also which terminate in the cord are not necessarily confined 

 to one ganglion. According to Langley and Anderson, a single fibre may send 



