CHAPTER IV 
THE NERVOUS SYSTEM 
SPINAL CORD 
HE spinal cord extends the whole length 
of the vertebral canal and ends near the end 
of the tail as a thin, round thread. It 
varies in thickness and shape in cross section, being 
nearly always elliptical, but at places approach- 
ing a circle. Large, spindle-formed thickenings of 
about equal diameter are present in the cervical 
and lumbar regions. 
A cauda equina is absent in the alligator, the 
nerves of the large tail leaving the cord like the 
intercostals. 
On its ventral surface the cord has a deep 
perpendicular fissure, the fissura ventralis, that 
extends almost to the center; it extends even 
along the reduced region in the tail. A vascular 
membrane extends into this fissure. 
A shallow but distinct furrow extends along 
the dorsal side of the cord, parallel to which, on 
either side, is a fine, linear furrow. 
The first two spinal nerves have no dorsal roots, 
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