324 PHYSIOLOGY. 



the head leave the cord by the first five dorsal nerves, pass through the 

 stellate and inferior cervical ganglia, go up in the cervical sympathetic 

 as preganglionic fibers to the first cell station, the superior cervical 

 ganglion. From here postganglionic fibers go to the Gasserian 

 ganglion and in the trigeminus and its branches. Other fibers go 

 from the superior cervical ganglion on the walls of the carotid artery 

 and its branches. 



The constrictors of the ear come from the sympathetic; go by 

 the cervical plexus in its second and third branches and to the ear by 

 the auriculo-cervical. 



Vasoconstrictors of the Extremities. The vasoconstrictors of the 

 upper extremities leave the cord by the dorsal anterior roots from the 

 fourth to the tenth, go in the sympathetic to stellate ganglion, then 

 into the brachial plexus and the nerves which leave it; some do not 

 enter the sympathetic but leave the cord directly with the roots of the 

 nerves of the upper extremity. The vasoconstrictors of the lower 

 extremities leave the cord by the roots of the lower dorsal and the first 

 three lumbar, enter the thoracic and abdominal sympathetic and go 

 into the sciatic. Some fibers leave the cord directly with the roots of 

 the sciatic and crural without entering the sympathetic. 



Vasoconstrictors of the Abdominal Viscera. The vasoconstrictors 

 come from the dorso-lumbar cord. The vasomotors of the abdominal 

 viscera leave the dorsal cord from the lower fifth dorsal down and the 

 lumbar cord by the first two or three roots. Branches from the fifth 

 to tenth thoracic ganglia form the splanchnics, then go into the cceliac 

 plexus and from there to the various organs as the intestines, liver, 

 spleen and kidneys in the plexuses which surround these organs. Some 

 vasoconstrictors descend by the vagus to the stomach, the intestine 

 and the kidney. The vasoconstrictors of the genital organs leave the 

 cord by the second and third sacral and go in the hypogastric plexus, 

 where they pass to their destination. 



If one splanchnic be cut in the abdominal cavity, the blood- 

 pressure sinks 30 or 40 millimeters; if the second be cut the pres- 

 sure immediately drops to 10. If the peripheral end of the cut 

 nerve be irritated, the aortic pressure ascends and reaches as great a 

 height as before section. Through the paralysis of the abdominal 

 vessels the portal system is filled with blood, the small intestinal 

 vessels are strongly injected, the blood-vessels of the kidneys are 

 dilated, and the renal tissue is red and congested. 



By these experiments it was established that the splanchnic is 

 the most important of all the vasoconstrictor nerves, and therefore an 



