The ganglia which form the main centres of the sympathetic nervous system lie in two rows (s, Fig. 1, and sy, Fig. 2), one on each side of the bodies of the vertebræ. Each ganglion is united by a nerve-trunk with the one in front of it and the one behind it, and so two chains are formed reaching from the base of the skull to the coccyx. In the trunk region these chains lie in the ventral cavity, their relative position in which is indicated by the dots sy in the diagrammatic transverse section represented on p. 9 in Fig. 2.

Name the seventh pair of cranial nerves. To what parts are they distributed ?

What is the eighth pair called? What are their functions? Where do they end?

Name the ninth pair. State their distribution.

Name the tenth pair. State their distribution.

Name the eleventh pair. Where do they arise? How do they get into the brain-case? With what nerves do they leave the brain-case? State their distribution.

Name the twelfth pair of cranial nerves. State their distribution.

Each sympathetic ganglion is united by branches to neighboring spinal nerves, and near the skull to various cranial nerves also; from the ganglia and their uniting cords arise numerous trunks, which in the thorax and abdomen form networks, from which nerves are given off to the organs situated in those cavities. Many sympathetic nerves finally end in the Walls of the blood-vessels of various organs. To the naked eye they are commonly grayer in color than the cerebro-spinal nerves.

By means of the junctions between the cranial and spinal nerves and the sympathetic system the brain is enabled to control the parts supplied by the sympathetic system.