CHAPTER VI. ' 



NEUROLOGY. 



The subject of this chapter, the nervous system, includes those 

 organs which may be regarded as receiving and interpreting 

 impressions ; stimulating and regulating the vital functions. The 

 nervous system in the broad sense consists of three sets of organs, 

 peripheral, central, and communicating, the function of the latter 

 being to establish a communication between the other two ; that 

 of the first to receive and deliver impressions ; and that of the 

 second to generate the nervous force. In other words, the system 

 comprises peripheral end-organs, nerves, and nerve centres ; it is 

 with the two latter that we have more immediately to deal. The 

 nervous system is divided into two minor systems — the Cerebro- 

 spinal, which is to a considerable extent influenced by the will of 

 the animal ; and the Sympathetic, or ganglionic system, which 

 comprises the nerves of organic life, which are not directly influ- 

 enced by the will. Each of these has its own central and 

 peripheral organs. 



In the first, the centre is made up of two portions — one large 

 and expanded, the brain or encephalon, which occupies the cranial 

 cavity; the other, the spinal cord, is elongated and continuous 

 with the brain, being lodged in the canal of the vertebral column. 

 The communicating portion of this system consists of the cerebro- 

 spinal nerves, which leave the axis in symmetrical pairs, and are 

 distributed to the voluntary muscles, and the organs of common 

 sensation, and special sense. 



In the second, the central organ consists of a chain of ganglia 

 connected by a nerve cord, which extends from the head to the 

 coccyx, on each side of the spine. The nerves of this system are 

 distributed to the involuntary muscles, mucous membranes, viscera, 

 and blood-vessels. The two systems have free intercommunica- 

 tion, ganglia being placed at the junctions. 



465 2 H 



