164 FUNCTIONS OF THE NERVOUS SYSTEM. 



Pachydermata, Carnivora, and Quadrumana, that regular convolutions can be 

 said to exist. The correspondence between the bulbous expansion of the 

 Olfactive Nerves in Mammalia, and the Olfactive lobes of the lower Vertebrata, 

 is made evident by the presence, in both instances, of a cavity which commu- 

 nicates with the lateral ventricle on each side ; it is in Man only that this cavity 

 is wanting. The external form of the Corpora Q,uadrigemina of Mammalia, 

 differs from that of the Optic ganglia of Birds, owing to the division of the 

 former into anterior and posterior eminences, (the nates and testes) ; and there 

 is also an internal difference, occasioned by the contraction of the cavity or 

 ventricle, which now only remains as the Aqueduct of Sylvius. The Cere- 

 bellum is chiefly remarkable for the development of its lateral parts or hemi- 

 spheres ; the central portion, sometimes*called the vermiform process, is rela- 

 tively less developed than in the lower Vertebrata, in which it forms the whole 

 of the organ. 



XIV. Functions of the Cephalic Nerves. 



219. Before proceeding to inquire into the functions of the different parts of 

 the Encephalon, it seems desirable to bring together what is known in regard 

 to the functions of the Nerves specially connected with them ; so that, by 

 tracing their connections, we may be able to obtain some light upon this very 

 obscure, though most interesting and important subject. 



220. That the First pair, or Olfactory nerves, minister to the sense of Smell, 

 has long been known; yet it could not be . predicated without experimental 

 inquiry, that it is not a conductor of the impressions which produce ordinary 

 sensation; nor that it is destitute of all power of exciting muscular movement, 

 either by direct or reflex action. Anatomical examination of the distribution 

 of this nerve, proves that it is not one which directly conveys motor influence 

 to any muscles ; since all its branches are distributed to the membrane lining 

 the nasal cavity. Experimental inquiry leads to the same result ; for no irri- 

 tation of the peduncles or branches excites any muscular movement. Further, 

 no irritation of any part of this nerve excites reflex actions through other 

 nerves. Again, it is not a nerve of common sensation; for animals exhibit no 



[Fig- 34. 



A view of the First pair, or Olfactory Nerves, with the Nasal Branches of the Fifth pair : 1, frontal sinus; 

 2, sphenoidal sinus; 3, hard palate ; 4, bulb of the olfactory nerve; 5, branches of the olfactory nerve on 

 the superior and middle turbinated bones; G, spherio-palatine nerves from the second branch of the fifth 

 pair; 7, internal nasal nerve from the first branch of the fifth: 8, branches of 7 to the Schneiderian mem- 

 brane; 9. ganglion of Cloquet in the foramen incisivum; 10, anastomosis of the branches of the fi.th pair 

 on the inferior lurbinated bone.] 



