A STUDY OF THE NERVOUS SYSTEM 



269 



lobe, while those from the left eye go to the right lobe. 

 These fibers finally communicate with cells in the forebrain. 



Hindbrain. Extending across the dor- 

 sal surface of the hindbrain just behind 

 the optic lobes is a ridge of brain tissue 

 called the cer-e-bel'lum (Latin cerebellum 

 = little brain). To the remainder of 

 the hindbrain is given the name me- 

 dul'la ob-lon-ga'ta (Latin medulla = 

 marrow -f- oblongata = oblong). Seven 

 pairs of nerves are connected with the 

 medulla. The third (arising from mid- 

 brain), fourth, and sixth pairs are dis- 

 tributed to the muscles that move the _, 



FIG. 125. Dorsal View 



eyeballs. The fifth and seventh nerves of Frog's Brain. 



bring to the brain messages from the 



sense organs in the skin and mucous 



membrane of the head region, and carry 



impulses from the brain to the muscles 



of the jaws and eyelids and face. The 



eighth pair of nerves, called au'di-to-ry 



(Latin audire = to hear), connect the 



ear with the brain. The ninth pair 



supply the tongue and pharynx, and 



hence are called glos'so-phar-yn-ge'al 



(Greek glossa = tongue + pharyngeal = v > VII = fifth and sev- 



referring to the throat). The distribu- nerve^ 8 f 



tion of the tenth pair of nerves is the VIII = eighth pair 



widest of any of the brain or cranial i** ^ 



nerves, and for this reason it has been ix, x= ninth and 



named the va'qus (Latin, vagus = wan- tenth P airs 



i \ -r, 01 -,. ; -i , i of nerves, 



dering). Its fibers are distributed to 



the lungs and air passages, to the heart and blood vessels, 

 and to the organs of digestion. 



The Spinal and Sympathetic Nerve Systems. The posterior 

 end of the medulla is continuous with the cylindrical spinal 



HH= cerebellum. 



Lol = olfactory 

 lobes. 



Med spinal cord. 



MH = midbrain (op- 

 tic lobes). 



NH = medulla ob- 

 longata. 



VH = forebrain (cer- 

 ebral hemi- 

 spheres) . 



J=first pair 

 (olfactory) 

 nerves. 



