THE SPINAL CORD. 63 



The cord is comparatively very slender in the region 

 between the two enlargements, and, in );he tail region, 

 gradually tapers off ; but it extends to the end of the 

 vertebral column, there being no cauda equina j along its 

 ventral aspect the cord presents a well-marked median 

 anterior fissure. 



163. Carefully raise a bit of the cord in the region of 

 the lumbar enlargement ; note that the spinal trunks 

 are formed by the union, outside the neural canal, of 

 a ventral [anterior) and dorsal {posterior") root, and that 

 each root in turn arises from the cord by a number of 

 small separate bundles. To see the roots well a hand- 

 lens will be found of use. 



164. Examine the roots in the middle dorsal region, 

 and in the neck. In the former they are very small. 



165. Carefully trace a pair of roots in the middle 

 dorsal region. They will be found to reach a compara- 

 tively large spinal ganglion which lies, imbedded in pig- 

 mented connective tissue, in one of the hollows found 

 along the vertebral column, between the necks of the 

 ribs. From the outer side of the ganglion proceed the 

 two trunks already referred to (156); they are con- 

 siderably larger- than the roots entering the ganglion. 



Next trace out some roots in the anterior cervical 

 region and the cervical and lumbar enlargements, and 

 note the ganglia attached to them. 



166. Cutting away the bone more freely, remove 

 parts of the spinal cord, and make, sections of it at 

 different levels. Note the well-marked anterior fissure ; 



