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IOWA ACADEMY OP SCIENCE 
About the l)eginniiig’ of the sixth day, the anlagen of the secondary 
or permanent sympathetic trunks arise in the cervical and in the thoracic p' . 
region, as ganglionic enlargements on the median sides of the spinal 
nerves just proximal to the origin of the communicating rami. These 
ganglionic enlargements are at first independent of each other, but be- 
come connected later by longitudinal commissures. There is as yet no 
evidence of the anlagen of the secondary sympathetic trunks posterior 
to the thoracic region. 
As the secondary sympathetic trunks increase in size and importance, 
the primary sympathetic trunks decrease. At the close of the sixth 
day the anlagen of the secondary sympathetic trunks appear through- 
out the entire lengtli of the body. The primary sympathetic trunks ^ 
have become less conspicuous and in the thoracic region have completely 
disappeared. 
The prevertebral plexuses are derived directly from the primary 
sympatlietic trunks. About the middle of the fourth day, from the f 
suprarenal Imdies posteriorly, cells become separated from the primary 
sympathetic trunks and, migrating ventrally, become aggregated along 
the ventro-lateral aspects of the aorta and give rise to the prevertebral 
plexuses. These cell-aggregates show their greatest development in the 
sacral region. This condition in birds is obviously correlated with the 
enormous development of the ganglion of Remak. This ganglion arises 
toward the close of the fourth day, as an oval cell-column lying in the 
mesentery just dorsal to the rectum. Its greatest development occurs 
in the posterior region. It increases in size very rapidly until at the 
close of the fifth day it has become a large and conspicuous column of 
closely aggregated cells, with a maximum diameter of about 85 micra. 
Its diameter decreases anteriorly until it ends in the region of the geni- 
tal ridges in a slender cellular cord which Remak has called the intestinal 
nerve ( Darmnerv ) . 
The ganglion of Remak was described by Onodi and by His, Jr., but 
as far as I have been able to learn, the cells composing it have never 
l)een traced to their source. My preparations show conclusively that ^ 
the cells giving rise to this ganglion are derived directly from the anlagen 
of the hypogastric plexus. 
ITis, Jr. has expressed the opinion that tlie elements composing the 
primary sympathetic trunks are resolved into the ganglia and the nerves ^ 
of the peripheral sympathetic plexuses. In view of the comparatively 
enormous development of the prevertebral plexuses and the ganglion of 
Remak, this is obviously the fate of the primary sympathetic trunks in 
the posterior region of the body. There is no evidence, however, of 
