122 THE COMMON FROG. [chap. 



of ready adjustment to enable the animal to secure 

 its insect prey. 



6. The sixth and last segment of the brain, the 

 medulla oblongata, is also relatively large, and is ex- 

 posed to view through the rudimentary development 

 of the cerebellum which, as has been said, overlaps it 

 in man. (Fig. 74, i) 



It has been already said, that in man and the higher 

 animals there are nerves supplying the orbital muscles 

 and different parts of the face. 



The eyeball in man is moved by six little muscles, 

 four straight (the recti) and two oblique, one being the 

 upper, the other lower, oblique. 



Now a nerve called the thu'd, because it follows the 

 first two (olfactory and optic), goes from the brain to 

 all the orbital m.uscles except the upper oblique and 

 the outer rectus. 



Another nerve, th.^ fourth, proceeds to the upper 

 oblique muscle only. 



Th.Q fifth nerve is a very large one, and supplies the 

 nose, tear-gland, eyelids, upper and lower jaws, tongue, 

 and teeth. 



T\\^sixtJi nerve is a vdry small one indeed, being ex- 

 clusively applied to the outer rectus muscle of the orbit. 



The seventh nerve is, in human anatomy, reckoned 

 as part (the portio dura) of the auditory nerve. It 

 sends fibres to the face. 



The eighth nerve is a very complex structure, and 

 consists of^ at least, three ncrv^es united together, all 

 arising from the medulla oblongata. It sends branches 

 to the parts about the throat as well as to the organ 

 of voice, to the lungs, the stomach, and the heart. 



