420 ANATOMY IN A NUTSHELL. 



communicating artery of the circle of Willis and is called the ganglion of Ribes; 

 the Lower one, the ganglion of impar is in front of the coccyx. This frame work 

 mighl be compared to a chain of beads. The thread upon which tho beads are 

 strung is called the sympathetic nerve and the beads represent the ganglia. In 

 the cervical region there are only three, in the dorsal region eleven or twelve, 

 in the lumbar region four, and in the sacral region five. There ought to be 

 thirty-one of these, one for each spinal nerve, but on account of the coalesecence 

 of several into one, there are only twenty-three. 



There is only one nervous system but it has three divisions: (1) the cen- 

 tral consisting of the brain and spinal cord; (2) the twelve cranial nerves and 

 the thirty-one spinal nerves is the peripheral system; and (3) the rest is called 

 i lie sympathetic system. The frame work of the sympathetic is connected to 

 the anterior branch of the spinal nerves by rami communicantes. Each gang- 

 Lion giv< -s off a ramus to the anterior branch of the spinal nerve which is graj , 

 and the anterior branches of the spinal nerves in the dorsal and lumbar regions 

 give off rami communicantes, which are white, to the ganglion of the syntpa- 

 th< tic. Gray rami communicantes are indigenous to every part of the spinal 

 cord, while the white are indigenous to the dorsal and lumbar regions. Every 

 branch that leaves a ganglion is called a ramus efferent, and these rami efh ren- 

 tes have special names, for instance, those going to anterior branches of the 

 first four cervical nerves are called rami communicantes and those that leave 

 1 1 it se ganglia and go to the heart are called cardiac branches. The gray rami 

 communicantes after theypass to the anterior branch of the spinal nerves fol- 

 low these- nerves to their destination. Those that are given off to bone, facia, 

 Ligament, or blood vessels are called gray rami communicantes, for instance, 

 the musculo-cutaneous nerve- of the brachial plexus gives off a branch that goes 

 into the nutrie nt foramen of the- humerus; this is an < xample of the gray rami 

 communicantes. Tin- anterior crural nerve and the obturator nerve give off 

 branches to the femoral artery; these- branches are also examples of gray rami. 

 The nerve- to the popliteus muscle- sends a branch with an artery into the tibia. 

 This is another example of gray rami. The- parietal layer of the peritom inn 

 gets its nerv< supply from the- gray rami. Here we apply Hilton's law — the 

 nerv< which supplies th< integumenl supplies the muscle- beneath the integu- 

 nient and the Lining beneath the muscle, and this nerve- that supplies the lining 

 does it through th< branch's called gray rami. The sympathetic nerve is 

 developed from the ganglia upon tin posterior nerve root of the spina! cord. 

 0n< -i t of physiologists say ii is d< veloped from the suprarenal capsule-. The 

 sympathetic nerve gets to its destination by following the- somatic nerves or 

 blood v< ssels. The sympathetic nervous system, like the central system, con- 

 sists of nerve <■< lis and nerve fibres which are- either motor, senseuy or com- 

 pound. Tin- trophic cells are- in the veite-bral ganglion of the- sympathetic 

 nerve. The motor cells of the sympathetic originate in the' ganglion of the 

 sympathetic and some observers say thai the sensory fibres of the- sympathetic 

 originate here also, but others say tin sensory are- in the- cells of the- spinal 

 ganglia. In tlii> Latt< r case (which is probably true-) reflex action can not take 

 place within the- sympathetic without involving the spinal nerves. The- super- 



