CHAPTER IV 



the nervous system 



Spinal Cord 



THE 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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