IOWA ACADEMY OP SCIENCE 
221 
pei’iplieral migration of cells from the primary sympathetic trunks in 
the anterior region. While there may he some migration posteriorly 
along the primary trunks, it is more probable that most of the cells in 
the anterior region are withdrawn into the secondary sympathetic 
trunks. 
The vagal sympathetic plexuses; viz., the cardiac plexus and the sym- 
]mthetic plexuses in the walls of the visceral organs, arise from cells 
which migrate from the vagus ganglia and the w^alls of the hind-brain 
along the fibers of the vagi. While medullary cells are migrating from 
the neural tube into the ventral roots of the spinal nerves, cells may 
also be traced from the walls of the hind-brain into the rootlets of the 
vagus and of the spinal accessory nerves. With similar cells which wander 
out from the vagus ganglia, these cells migrate peripherally along the 
vagi. In the thoracic region cells may be traced from the vagus trunks 
into the walls of the oesophagus where they become aggregated into cell- 
groups which constitute the anlagen of the myenteric and the submucous 
plexuses. These observations do not differ materially from the writer’s 
ol)servations on mammalian embryos. In mammalian embryos cells may 
be traced posteriorly from the anlagen of the myenteric and the sub- 
ucous plexuses in the walls of the oesophagus and the stomach. These 
cells obviously give rise to the sympathetic plexuses in the walls of the 
intestine. In the chick, sympathetic cells cannot be traced posteriorly 
in the walls of the digestive tube with the same degree of definiteness. 
It is probable, however, that the cells giving rise to the sympathetic 
plexuses in the walls of the intestine are derived largely from this source. 
On the other hand, it is probable ,in view of the enormous development 
of the ganglion of Remak, that in birds many of the cells taking part in 
the development of the sympathetic plexuses in the posterior region of 
the intestine are derived directly from this ganglion. 
At the bifurcation of the trachea, the vagus trunks bend laterally 
and ventrally round the bronchi until they come to lie close together 
along the ventral aspect of the oesophagus. A slender branch of each 
vagus trunk continues posteriorly from the bifurcation of the trachea 
along tlie lateral wall of the oesophagus. In transverse sections through 
the lungs, fibers accompanied by numerous cells may be seen to bend 
from these branches into the tissues of the lungs. These cells obviously 
give rise to the pulmonary plexuses. 
About the close of the fifth day, in transverse sections tlirough the 
heart, cells may be traced ventrally from the vagi toward the dorsal 
surface of the heart. In later stages these cells become aggregated into 
distinct groups in the septum of the atria and give rise to the cardiac 
plexus. 
