168 Mammalia. 



origin of the Seventh Pair of Nerves. This pair of nerves con- 

 sists of two portions, named respectively Portio Mollis = 

 Auditory, and Portio 'D\x.vq.=^ Facial Nerve. The former is the 

 special nerve of the sense of hearing, being distributed ex- 

 clusively to the internal ear ; the latter is the motor nerve of 

 the face, and is situated a little nearer to the middle line than 

 the Portio Mollis. 



Immediately behind the Olivary body, a little further back 

 than the origin of the Seventh Pair of Nerves, will be seen the 

 superficial origin of two of the three components of the Eighth 

 Pair ofNerveSy viz. the Glosso-Pharyngeal and the Pneumogastric 

 or Vagus ; the third component, viz, the Spinal Accessory, 

 arises by several filaments from the lateral tract of the cord 

 below the Yagus. Of these three components the Glosso-pharyn- 

 geal is distributed, as its name implies, to the Tongue and 

 Pharynx, being the nerve of sensation to the mucous mem- 

 brane of the fauces and root of the Tongue ; and of motion to 

 the Pharyngeal muscles. The Pneumogastric has a more 

 extensive distribution than any of the other cranial nerves, 

 passing through the neck and cavity of the Chest to the 

 Abdomen : it is composed of both motor and sensory fila- 

 ments : it supplies the organs of voice and respiration with 

 motor and sensory fibres; and the Pharynx, GEsophagus, 

 Stomach, and Heart with motor fibres. The Spinal Accessory 

 consists of two parts ; one, the accessory part to the Yagus, 

 to whose pharyngeal and superior laryngeal branches it con- 

 tributes filaments ; the other the spinal portion, which is dis- 

 tributed to the Sternomastoid* and Trapezius! muscles. 



* The Sterno-mastoid is a muscle which passes obliquely across the neck, arises 

 by two distinct heads, from the Sternum and Clavicle (when present), and is in- 

 serted by a strong aponeurosis into the outer surface of the Mastoid process of 

 the Temporal bone : it is a flexor and depressor of the head. 



t The Trapezius is a muscle covering the upper and back part of the neck and 

 shoulders ; arising from the Occipital protuberance, ligamentum nuchse, and 

 spinous processes of cervical and dorsal vertebrae, and inserttd into the upper 



