,VI.] 



THE CRANIAL NERVES. 

 Fig. 42. 



127 



[Head op an Embryo Chick of the Third Day (Seventy- 

 Five Hours) viewed sideways as a Transparent Object. 

 (From Huxley.) 



'a. cerebral hemispheres. lb. vesicle of the third ventricle. II. 

 mid-brain. III. hind-brain, ff. nasal pit. a. optic vesicle. 

 b. otic vesicle, d. infundibulmn. e. pineal body. h. noto- 

 chord. V. fifth nerve. VII. seventh nerve. VIII. miited 



glossopharyngeal and pueumogastric nerves, 

 the five visceral folds. 



h 2, 3, 4, 5 



Tanch of the fifth nerve) is distributed to the first 

 sceral arch. 



The second mass (Figs. 42 and 67, VII) is the rudi- 

 ment of the seventh, or facial nerve, and of the audi- 

 tory nerve. It is the nerve of the second visceral arch. 



The two masses behind the auditory vesicle repre- 

 sent the glossopharyngeal and pneumogastric nerves 

 [Fig. 42, VIII, Fig. 67, G. Ph. and Pg.). At first 

 iinited, they subsequently become separate. The glosso- 

 jharyngeal supplies the third arch, and the pneumo- 

 gastric the fourth and succeeding arches. 



The later development of the cranial nerves has only been 

 ipartiaUy worked out, and we wiU confine ourselves here to a veiy 



