LESSON XI 

 THE NERVOUS SYSTEM AND INNERVATION 



1. The General Arrangement of the Nervous 

 System. — Tho sensory organs are, as we have seen, the 

 channels through which pai'ticular physical regents are 

 enabled to excite the sensory nerves with which these 

 organs are connected ; and the activity of these nerves is 

 evidenced by that of the central organ of the nervous 

 system, which activity becomes manifest as a state of 

 consciousness — the sensation. 



We have also seen that the muscles are instruments by 

 which a motor nerve, excited by the central organ with 

 which it is connected, is able to produce motion. 



The sensory nerves, the motor nerves, and the central 

 organ, constitute the greater part of the nervous system, 

 which, with its function of innervatinn, we nmst now study 

 somewhat more closely, and as a whole. 



The nervous apparatus consists of two sets of nerves 

 and nerve-centres, which are intimately connected together 

 and yet may be conveniently studied apart. These are the 

 cerebro-spinal system and the sympathetic system. 

 The former, or central nervous system, consists of the 

 brain (see Fig. 1), including with this the spinal bulb 

 or medulla oblongata, and spinal cord and the 

 cranial and spinal nerves, which are connected with 

 this axis. The latter comprises the chain of sym- 

 pathetic ganglia, the nerves which they give ofl', and 

 the various cords by which they are connected with one 



