182 OUTLINES OF EQUIN'E ANATOMY. 



Tical ganglion. The cervical nerves are eight in number. 

 The first or suboccipital emerges through the foramen in 

 the pedicle of the atlas, through which the vertebral artery 

 gains the spinal canal. It sends fibres to the auricular 

 nerves and to the superior cervical ganglion (situated under- 

 neath the ala of the atlas) . The second nerve emerges through 

 the foramen in the anterior part of the pedicle of the den- 

 tata. The third, fourth, and fifth nerves send fibres to form 

 the phrenic nerve, while fibres from the sixth, seventh, and 

 eighth, first dorsal, and sympathetic form the axillary plexus. 

 Each of these nerves after passing through its foramen 

 sends oif a superior branch to the structures above the ver- 

 tebrae, an inferior to those below. On the lateral part of 

 the cord as far down as the fifth cervical vertebra may be 

 seen the spinal accessory nerve which j^asses upwards, be- 

 tween the superior and the inferior roots of the nerves, 

 receiving fibres along its whole course from the cord as far 

 up as the medulla oblongata. 



After removing the cord and its membranes we may ex- 

 amine the superior vertebral ligament, which extends along 

 the upper surfaces of the vertebrae throughout the whole 

 canal. It becomes widened in becoming attached to each 

 intervertebral cartilage and is attached to the roughened 

 line on the centres of the upper part of the bodies of the 

 vertebrae, having on either side a venous sinus extending 

 along the whole length of the canal, sending a transverse 

 communicating branch under this ligament opposite the 

 centre of the body of each vertebra — also sending branches 

 outwards through each intervertebral foramen. These 

 sinuses anteriorly through the medium of the posterior 

 petrosal sinuses are connected to the cavernous sinus. 



