OLFACTORY NERVE. 



393 



C Glosso-pharyngeal, 

 8th. < Pneuraogastric (vagus, par vagum). 



( Spinal accessory. 

 9th. Hypoglossal (lingual). 



Functionally or physiologically the cranial nerves admit of division into 

 three groups, namely, nerves of special sense, nerves of motion, and com- 

 pound nerves, that is, nerves which contain fibres both of sensation and 

 motion. The nerves belonging to these groups are the following : 



f 1st. Olfactory. 



Special sense \ 2d. Optic. 



[ 7th. Auditory. 



3d. Motores oculorum. 

 4th. Pathetici. 



Motion \ 6th. Abducentes. 



7th. Facial. 



9th. Hypoglossal. 



Compound 



5th. Trifacial. 



8th. Glosso-pharyngeal. 



Pneumogastric. 



Spinal accessory. 



The fourth, facial, and eighth nerves were considered by Sir Charles 

 Bell to form a system apart from the rest, and to be allied in the functions 

 of expression and respiration. In consonance with this view he termed 

 them respiratory nerves, and he gave to that part of the medulla oblongata 

 from which they arise the name of respiratory tract. 



Fig. 176.* 



FIRST PAIR. OLFACTORY. 

 The olfactory nerve arises 

 by three roots ; an inner root 

 from the substantia perforata, 

 a middle root from a papil- 

 la of grey matter (caruncu- 

 la mammillaris), embedded 

 in the anterior lobe, and an 

 external root, which may be 

 traced as a white streak along 

 the fissure of Sylvius into 

 the corpus striatum, where 

 it is continuous with some of 

 the fibres of the anterior com- 

 missure. The nervous cord 



formed by the union of these three roots is soft in texture, prismoid in shape, 

 and embedded in a sulcus between two convolutions on the under surface of 

 each anterior lobe of the brain, lying between the pia mater and the arach- 

 noid. As it passes forwards it increases in breadth and swells at its extremity, 



* A view of the 1st pair or olfactory, with the nasal branches of the 5th. 1. Frontal 

 sinus. 2. Sphenoidal sinus. 3. Hard palate. 4. Bulb of the olfactory nerve. 5. 

 Branches of the olfactory on the superior and middle turbinated bones. 6. Spheno-pala- 

 tine nerves from the 2d of the 5th. 7. Internal nasal nerve from the 1st of the fnl'.. 8. 

 Branches of 7, to Schrieiderian membrane. 9. Ganglion of Cloquet in the foramen ind 

 sivum. 10. Anastomosis on the inferior turbinated bone of the branches of the 5th pair 



