The nervous apparatus designated by this name consists of a double cord placed on either side of the spinal column, the whole length of the neck, and in the interior of the thoracic and abdominal cavities. It is, as has already been stated, the nervous system of organic, vegetative, or nutritive life. Extending from the first cervical vertebra to the last vertebra of the sacrum, the great sympathetic enlarges at the level of each vertebra, and forms nervous ganglia, which communicate by external filaments with all the cranial or spinal pairs, and constitute by their internal filaments all the visceral nerves. This string of ganglia gives the great sympathetic the name of the ganglionic nervous system.

The great sympathetic forms the pharyngeal, the cardiac, the solar or caeliac and the hypogastric plexuses. These are the nervous centres of organic life.

The nerves emanating from the great sympathetic surround the arteries like a sheath, and penetrate with them into the organs. Some of these nerves, as has already been stated, are soft and of a grayish colour, and others are white and firm.