The nervous system consists of two parts, the Cerebro-spinal and the Sympathetic. The Cerebro-spinal consists of the brain and spinal cord, with all the nerves given off by them. These nerves extend to all parts of the body and form the means of communication between the muscles and the great nerve centre, the brain and spinal cord.

The Sympathetic consists of a number of ganglia or knots of nerve matter, which give off nerve fibres and form a chain on each side of the vertebral column from the skull to the pelvis, communicating by fibres with the cerebro-spinal system.

The nerves of the sympathetic system are distributed to the viscera and to the coats of the bloodvessels. The lungs, heart and upper and lower part of the alimentary canal receive nerves also from the cerebro-spinal system.