SYMPATHETIC SYSTEM IN TURTLES 



289 



merged with the anlagenof the sympathetic trunks (fig. 4,>S. C. R.). 

 In a few sections these cellular tracts were observed to unite with 

 the communicating rami just proximal to the point at which the 

 latter enter the sympathetic anlagen. 



The cellular tracts above described apparently have their ori- 

 gin in the spinal nerves. In a few instances at this stage fibers were 



^# 









i-SpR 



/^ ^Sy. 



Fig. 4 Transverse section through the anlage of the sympathetic trunk in 

 a sixteen-day embryo of Thalassochelys caretta. X 210. Ao., aorta; Ci2./ com- 

 municating ramus; S.C.R., secondary cellular tract extending from the spinal 

 nerve into the anlage of the sympathetic trunk; Sp.N., spinal nerve; Sy., anlage 

 of sympathetic trunk. 



observed to deviate from the spinal nerves along these cellular 

 tracts. These fibers may usually be recognized as ventral root 

 fibers. They deviate from the spinal nerves at a point so near the 

 union of the dorsal and the ventral nerve-roots that they may 

 readily be traced proximally as fibers of the ventral roots. 



