FUNCTIONS OF THE NERVOUS SYSTEM. 137 



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 coiliac 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. 



Functions of the nervous system. The nervous system is 

 the seat of intelligence, of sensation, and of motion; it is the 

 centre of action for the organism, and it presides over all the 

 phenomena which together constitute life. Its spinal and 

 superficial portions the cord and the nerves take part only 

 in the functions of sensation, of motion, and of organic life: 

 but the encephalon contributes at once to the material and 

 mental functions. 



Observers have succeeded in distinguishing in the nerves 

 and spinal cord the apparatus which is specially devoted to 

 sensation, from that which presides over motion. But the 

 knowledge which we have attained concerning the special 

 functions of the different parts of the encephalon is as yet 

 very limited, and for the most part hypothetical. Compara- 

 tive physiology teaches us that some portions are extremely 

 sensitive and irritable, while others are not affected by- 

 external agents. The medulla oblongata, the pons Varolii, 

 and quadrigeminal bodies, are most allied to the spinal cord, 

 and anatomy can follow thither the medullary fascicles en- 

 dowed with sensibility, but beyond them these same fascicles 

 become insensible in the greater and lesser brain, the optic 

 beds, &c. It appears that after having transmitted the external 

 impression, they change their nature, becoming an integral 

 portion of the organ in which the sensation is produced, and 

 submitted to the apprehension of the intelligence. We are 

 no less embarrassed if we attempt to specify the portions of 



