THE SPINAL CORD 399 



;ense organs. The cerebrum is the organ of the mind. 

 Through it we get the sensations of heat, light, sound, 

 touch, taste, etc., and the use of our voluntary muscles. 

 Twelve pairs of nerves (cranial nerves) pass from the 

 front of the cerebrum directly (that is, without going 

 through the srJinal cord) to the head, neck, and trunk. 



The midbrain is a rounded body lying under the cerebrum, and 

 connecting the forebrain with the hindbrain. 



The cerebellum (meaning, " little cerebrum") is the largest body of 

 the hindbrain, and occupies most of the space inside the ' ' base of the 

 skull. 7 ' It is covered over by the back lobes of the cerebrum, and its 

 surface looks much like that of the cerebrum. The cerebellum seems 

 to have special control of muscular movements, making the muscles 

 contract properly and in pairs (cf. 355). It thus causes the move- 

 ments of the body to be orderly and regular. 



The pons (from the Latin word for "a, bridge") is in front of the 

 cerebellum, and consists largely of bands of nerve fibers. These con- 

 nect the cerebrum, cerebellum, and bulb. 



The bulb, or medulla oblongata, is really the enlarged upper end of 

 the spinal cord, although it is within the cranium. It is below the 

 cerebellum, and consists of ganglia of the nerve cells and nerve fibers 

 that form the connection between the spinal cord and the brain. 



401. The Spinal Cord. The spinal cord (Fig. 295) is a 

 column of nerve tissue about % of an inch thick; in the 

 adult it occupies the cavity of the spinal column down to 

 the bottom of the 20th vertebra. The cord is not round, 

 but has two lengthwise depressions (one in front and one 

 in back) that make a cross section of it look like a capital 

 H. The outside of the spinal cord is white, from the 

 coverings of its nerve fibers. The inside of the cord con- 

 sists of gray cells, and its section also resembles an H. 

 At its upper end the cord enters the skull, and is enlarged 



