THE CIRCULATION. 325 



important regulator of the blood-pressure. The splanchnics supply 

 vasomotor fibers to the stomach, bowels, and kidneys. Irritation of one 

 splanchnic is sufficient to cause vasoconstriction in both kidneys. 



The viscera receive vasoconstrictor fibers from other sources, as 

 the vagus. Two weeks after section of both splanchnics beneath the 

 diaphragm, the blood-pressure is again found to be the same as that 

 of a normal animal. 



The elevation of a patient in bed may lead to a faint, because 

 the heart in a reclining position and the abdominal reservoir of blood 

 are on the same plane; but the erect position increases the work of 

 the heart because the abdominal reservoir of blood is lower.- 



Vasoconstrictors of the Thorax. They arise from the five upper 

 dorsal nerves, go out through the first thoracic ganglion, then through 

 the annulus of Vieussens to the inferior cervical ganglion, and pass to 

 the heart and lungs. But direct observation shows that the vasocon- 

 strictors of the lungs are not strongly developed. An obstructive lesion 

 of the left heart will elevate blood-pressure in the lungs. 



Vasodilators. The vasodilators originate from a principal cen- 

 ter, located in the medulla oblongata, and from subsidiary centers dis- 

 tributed throughout the spinal cord. 



The salivary glands receive their vasodilators from the glosso- 

 pharyngeal for the parotid and from the facial for the submaxillary. 

 The same nerves furnish vasodilators to the anterior two-thirds of the 

 tongue by a branch from the chorda tympani, and by the glosso- 

 pharyngeal to the posterior third of the tongue. The mucous mem- 

 brane of the lips, cheeks, palate, nasal fossa receive their vasodilators 

 from the trigeminus by the superior maxillary branch. These vaso- 

 dilators in the superior maxillary are the outflow in the facial which 

 goes to the spleno-palatine ganglion. The outflow of vasodilators in 

 the glosso-pharyngeal go to the otic ganglion, whence they pass into the 

 inferior maxillary to the mucous membrane of lips, cheeks, palate and 

 nasal fossa. 



Those for the ear leave the cord by the eighth cervical and the first 

 and second dorsal, go to the first thoracic and inferior cervical 

 ganglia up into the cervical sympathetic. The vasodilators of 

 the upper extremity leave the dorsal cord by the fifth, sixth, seventh 

 and eighth pair, and the vasodilators for the lower extremities by 

 the fifth, sixth and sever th lumbar pair in the dog. The vasodilators 

 of the abdominal viscera leave the cord from the second to twelfth 

 dorsal pair of nerves and from the first to second pair of lumbar nerves 

 and some enter the splanchnics. The vasodilators of the penis, nervi 



