344 



ALBERT KUNTZ AND O. V. BATSON 



normal size. In the thoracic portion of the region involved, small 

 sympathetic primordia occur associated \vith the ventral nerve- 

 roots in several segments. In those segments in which the ven- 

 tral nerve-roots are verj^ small or absent sympathetic primordia 

 are absent. 



Fig. 3 Transverse section from a segment of embryo number 3, in which 

 spinal ganglia and dorsal nerve-roots are absent. X 165. AO, aorta; CR, 

 communicating ramus; DR, dorsal ramus; A^, notochord; SY, sympathetic 

 trunk; VR, ventral root of spinal nerve. 



A. Camera lucida outline of a cross section of the remnant of the neural tube 

 {X) in the segment from which figure 3 is taken superimposed on a camera lucida 

 outline of the same magnification of a cross section of the neural tube (Y) a 

 few segments farther cephalad where it was not affected by the operation. 



