4:18 NERVOUS SYSTEM. 



General Arrangement of the Sympathetic System. 



Like the cerebro-spinal system, the sympathetic is com- 

 posed of centres and nerves, at least as far as we can judge 

 from its anatomy. The centres contain nerve-cells, most of 

 which differ but little from the cells of the encephalon and 

 spinal cord. The nerves are composed of fibres, the greater 

 part of which are identical in structure with the ordinary 

 motor and sensory fibres. The fibres are connected with 

 the nerve-cells in the ganglia, and the ganglia are connected 

 with each other by commissural fibres. These ganglia con- 

 stitute a continuous double chain, on either side of the body, 

 beginning above, by the ophthalmic ganglia, and termina- 

 ting below, in the ganglion impar. It is important to note, 

 however, that, the chain of sympathetic ganglia is not inde- 

 pendent, but that each ganglion receives motor and sensory 

 filaments from the cerebro-spinal nerves, and that some fila- 

 ments pass from the sympathetic to the cerebro-spinal cen- 

 tres. The general distribution of the sympathetic filaments 

 is to mucous membranes, and possibly to integument, to 

 non-striated muscular fibres, and particularly to the muscu- 

 lar coat of the arteries. As far as we have been able to 

 learn from anatomical investigations, there are no fibres de- 

 rived exclusively from the sympathetic which are distributed 

 to striated muscles, except those which pass to the muscular 

 tissue of the heart. Near the terminal filaments of the sym- 

 pathetic, in most of the parts to which these fibres are dis- 

 tributed, there exist numerous ganglionic cells. 



The general arrangement of the sympathetic ganglia and 

 the 'distribution of the nerves may be stated, sufficiently for 

 our purposes, very briefly ; still, a knowledge of certain ana- 

 tomical points 'is indispensable as an introduction to an in- 

 telligent study of the physiology of this system. 



In the cranium, are four ganglia; the ophthalmic, the 

 spheno-palatine, the otic, and the submaxillary. In the neck, 

 are the three cervical ganglia ; the superior, middle, and in- 



