GENERAL ARRANGEMENT OF THE SYMPATHETIC SYSTEM. 635 



CHAPTER XX. 



SYMPATHETIC NERVOUS SYSTEM SLEEP. 



General arrangement of the sympathetic system General properties of the sympathetic ganglia and nerves 

 Direct experiments on the sympathetic Vaso-motor centres and nerves Reflex vaso-motor phenom- 

 ena Vaso-inhibitory nerves Trophic centres and nerves (so-called) Sleep Condition of the brain 

 and nervous system during sleep Anaesthesia and sleep produced by pressure upon the carotid arteries 

 Differences between natural sleep and stupor or coma Regeneration of the brain-substance during 

 sleep Condition of the organism during sleep. 



LIKE the cerebro-spinal system, the sympathetic is composed of centres, 

 or ganglia, and nerves, at least as far as can be seen from its anatomy. The 

 ganglia contain nerve-cells, most of which differ but little from the cells of 

 the encephalon and spinal cord. The nerves are composed of fibres, some 

 of which are nearly identical in structure with the ordinary motor and sen- 

 sory fibres, while many are the so-called gelatinous 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 constitute a continu- 

 ous chain on either side of the body, beginning above, by the ophthalmic gan- 

 glia, and terminating below in the ganglion impar. It is important to note, 

 however, that the chain of sympathetic ganglia is not independent, but that 

 each ganglion receives motor and sensory filaments from the cerebro-spinal 

 nerves, and that filaments pass from the sympathetic to the cerebro-spinal 

 system. The general distribution of the sympathetic filaments is to mucous 

 membranes and possibly to integument to non-striated muscular fibres, 

 and particularly to the muscular coat of the arteries. As far as has been 

 shown by anatomical investigations, there are no fibres derived 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 sympathetic, in most of the parts to which these fibres are distributed, 

 there exist large numbers of ganglionic cells. 



The general arrangement of the sympathetic ganglia and the distribution 

 of the nerves may be stated very briefly ; but a knowledge of certain anatom- 

 ical points is indispensable as an introduction to an intelligent study of the 

 physiology of this system. 



In the cranium, are the four cranial ganglia ; the ophthalmic, the spheno- 

 palatine, the otic and the submaxillary. In the neck, are the three cervical 

 ganglia ; the superior, middle and inferior. In the chest, are the twelve tho- 

 racic ganglia, corresponding to the twelve ribs. The great semilunar ganglia, 

 the largest of all and sometimes called the abdominal brain, are in the abdo- 

 men, by the side of the creliac axis. In the lumbar region, in front of 

 the spinal column, are the four lumbar ganglia. In front of the sacrum, are 

 the four or w five sacral, or pelvic ganglia ; and finally, in front of the coccyx, 

 is a small, single ganglion, the last of the sympathetic chain, called the gan- 

 glion impar. Thus, the sympathetic cord, as it is sometimes called, consists 

 of twenty-eight to thirty ganglia on either side, terminating below in a 

 single ganglion. 



