50 



PHYSIOLOGY AND MORPHOLOGY OF ANIMALS. 



First pair. — Olfactory = Special sense of smell. 



Second pair. — Optic = Special sense of sight. 



Third, fourth, and sixth pairs. — Motors of the eye. 



Fifth pair. — Trigemini = Common sensory of the face. 



Seventh pair. — Facial = Common motor of the face. 



Eighth pair. — Auditory = Special sense of hearing. 



Ninth pair. — Glosso-phary ngeal (gustatory) = Special 

 sense of taste. 



Tenth pair. — Vagus or pneumogastric = Sensory and 

 motor of the heart, lungs, and stomach. 



Eleventh pair. — Recurrens = Motor. 



Twelfth pair . — Hypoglossal = Motor of the tongue. 



In Fig. $$ we give a diagram showing general distri- 

 bution of these nerves. The origins, as seen in Fig. 17, 

 page 33, are near together. In this Fig. 33 the base of 

 the brain, and especially the medulla, are drawn out so 

 as to separate these origins. In Fig. 34 the medulla is a 

 little drawn out. Fig. 17, page 33, shows their natural 

 position. 



Description. — 1. The olfactory nerve, the only one 

 which comes from the cerebrum, is observed to pass for- 

 ward beneath the frontal lobe (Fig. 17), on the base of 

 the skull, until it reaches just above the nasal cavity 

 and on each side of the crista galli. There it throws 

 out a great number of small branches (Fig. 33, 1) through 

 the cribriform (colandered) plate, to be distributed to the 

 mucous membrane of the upper cavities of the nostrils. 

 Its function is to respond to the impression of odorifer- 

 ous vapors. 



Even in man it is seen to swell a little at the end. 

 As we pass down the vertebrate scale, by the increasing 

 size of this swelling it loses entirely its character as a 

 nerve and becomes a great lobe — the olfactory lobe of 

 the brain. 



2. Optic Nerve. — As already said (page 41), this arises 



