HISTOGENESIS OF SYMPATHETIC SYSTEM act 
ing ganglion of the sympathetic trunk. In the first of these 
cases, the intermediate portion of the wall of the neural tube 
which normally gives rise to the lateral cell-column was left 
intact. In this case, the primordium of the sympathetic trunk 
is of approximately normal size. In the second case, a consid- 
erable portion of the tissue which normally gives rise to the 
lateral cell-column was destroyed. In this case the primordium 
of the sympathetic trunk is correspondingly small. In the third 
case, all the tissue which normally gives rise to the lateral cell-col- 
umn was destroyed. Although numerous cells having their 
origin in the ventral portion of the neural tube advance periph- 
erally along the slender ventral nerve, none of them deviate 
from the course of these fibers; consequently, the primordium 
of the sympathetic trunk is absent. These observations strongly 
suggest that the major portion of the cells which enter the pri- 
mordia of the sympathetic trunks are derived from the inter- 
mediate portion of the wall of the neural tube which gives rise 
to the preganglionic visceral efferent neurons. 
Further evidence regarding the exact sources of the cells which 
give rise to the ganglia of the sympathetic trunks is afforded 
by an embryo of the chick (10) in which the ventral portion 
of the neural tube was more or less completely destroyed 
unilaterally throughout a series of segments. In some of these 
segments the neural crest was destroyed, while in others enough 
of the neural-crest material was left to give rise to a spinal gan- 
glion of nearly normal size. The dorsal portion of the neural 
tube is somewhat distorted in all of these segments, but rela- 
tively little tissue in this portion was destroyed. Figure 5 illus- 
trates the conditions observed in a section through a segment in 
which the portion of the wall of the neural tube which normally 
gives rise to the ventral cell-column was almost or quite com- 
pletely destroyed unilaterally. The spinal ganglion and dorsal 
nerve-root also are absent. Some fibers may be traced from the 
intermediate portion of the wall of the neural tube, which is 
well preserved in this segment, directly toward the dorsolateral 
aspect of the aorta into the primordium of the sympathetic 
trunk (fig. 5, sy) which comprises an aggregate of cells quite 
