AND PHYSIOLOGY. 



331 



upper part of the spinal column, and afterwards enters the 

 cranium. After keeping company with the par vagum for a 

 part of its course, it is distributed to some of the muscles upon 

 the head and face. 



594. Lingual. — The lingual nerve plunges its branches 

 deeply into the fibers of the tongue, and communicates with a 

 branch of the trifacial. 



irw. « . i *i «™ , Fig. 318. 



595. Spinal Cord —The spinal cord 



is that portion of the cerebro-spinal axis 

 contained within the channel made by 

 the foramina, or openings of the verte- 

 bra. It extends from the medulla ob- 

 longata just at the base of the skull, to \ \^ 

 the second lumbar vertebra, and has an & f 

 average diameter of half an inch. It Portion of the Spinal Cord 



° and Origin of one Pair of 



has the general appearance of a flattened Nerves, a, spinal Cord. &, 



n i . t . i . .. Posterior Root, c, Ganglion. 



cord, but on a closer inspection it ap- ^ Anterior Eoot ^ Trunk 

 pears to be made up of two smaller cords, formed h ? botn - Branch, 

 called the lateral cords, nearly separated by two clefts, called 

 the anterior and posterior median fissures. This cord is not 

 perfectly uniform in its size, but presents two enlargements, 

 one at the point where the nerves are given off to the upper 

 extremities, and the other near the lower end of the cord. 



596. Microscopic Structure of the Spinal Cord— In 

 anatomical structure we find the spinal cord and spinal nerves 

 are made up of two kinds of nervous matter, the white and 

 the gray, and also that each pair of these nerves arises by 

 an anterior and a posterior root. The posterior root is made 

 up of gray nervous tissue, and is called the sensitive root, 

 since it gives the sense of feeling to the parts where it is dis- 

 tributed ; the anterior root of w T hite fibers is called the mo- 

 tor root, because it imparts motion to the different muscles of 



594 Describe the lingual. 595. What is, the spinal cord ? How many fissures has the 

 spinal cord? How many enlargements? 596. What is the microscopic structure ot the 

 spinal cord? Which is the sensitive and which the motor root? 



