TENTH LECTURE. 



THE NERVOUS SYSTEM. 



550. ALL the actions of the Hving body are governed, more or less, 

 by the nervous system, which consists of two distinct portions ; the 

 cerebrospinal, and the sympathetic or ganglionic. The brain is the great 

 centre of the nervous system, and the special senses, such as smell, 

 taste, &c., are connected with and controlled by it. Two of these 

 special organs, i.e. the eye and the ear, will be noticed in this lecture. 



551. The Cerebro-spinal system, {Plate XXXIV., A. to D.) 

 embodies the brain, the spinal-cord, and the nerves given* off from 

 each. Those from the spinal-cord are for sensation and motion, 

 whilst from the brain, as already indicated, there arises the nerves 

 of special sense. 



552. The Sympathetic or Ganglionic system, (Plate XXXIV., E.j 

 or the nerves of organic life, are not immediately under the influence 

 of the will, and are made up of a double chain of knots or ganglia. 

 They run through the length of the body, on each side of the 

 back-bone, and give off fibres to control the involuntary movements of 

 the internal organs, such as the heart and blood-vessels, respiratory 

 and digestive organs, &c., these fibres having free communication 

 with the spinal nerves. 



553. The Nerve Tissue itself is composed of both a fibrous and 

 a cellular structure ; the latter, or grey substance, is found in the 

 outer portions of the convolutions of the brain, and in the middle 

 of the spmal cord and the ganglionic nerve centres ; while the fibrous 

 substance is both white and grey, and is found m the white matter of 

 the brain and spinal-cord. 



