SYMPATHETIC TRUNKS IN CHICK 



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segment from the level of the anterior to the level of the posterior 

 limb-buds. Ventral nerve-roots are present bilaterally or uni- 



Fig. 2 Transverse section from a segment of embryo number 2, in which two 

 neural canals are present and spinal ganglion and dorsal nerve-root are absent. 

 X 165. AO, aorta; CR, communicating ramus; DR, dorsal ramus; A', notochord; 

 P, prevertebral plexus; SY, sympathetic trunk; VR, ventral root of spinal nerve. 



laterally in every segment in which there remains an appreciable 

 remnant of the neural tube. Some of these ventral nerve-roots 

 comprise relatively few fibers; others are larger, but none are of 



