222 
IOWA ACADEMY OP SCIENCE 
Tlie above observatioris have shown that in birds, as in inamals, cells 
migrate peripherally from the neural tube and the cerebro-spinal ganglia, 
and that some of these cells give rise to the sympathetic nervous system. 
The cells giving rise to the sympathetic trunks and the prevertebral 
plexuses, including the ganglion of Remak, migrate peripherally along 
the spinal nerves, while the cells giving rise to the vagal sympathetic 
plexuses migrate peripherally along the vagi. The great majority of 
these migrant cells are the ^‘indifferent” cells of Schaper, while a few 
cells occasionally are found among them which answer to the descrip- 
tion of the “neuroblasts” of Schaper. This I have also shown to be the 
case in mamals. Mitotic figures occur occasionally along the paths of 
migration and in the sympathetic anlagen. We are not to suppose, 
therefore, that all the cells taking part in the development of the sym- 
pathetic system actually migrate as such from their sources in the 
neural tube and the cerebro-spinal gangia. Doubtless, a goodly number 
arise by the mitotic division of •“indifferent” cells along the course of 
migration. Inasmuch as these migrant cells are the ‘‘indifferent” cells 
and the “neuroblasts” of Schaper, they are homologous with the cells 
giving rise to the neurones and the neuroglia cells in the central nervous 
system. Therefore, the sympathetic system bears a direct genetic rela- 
tionship to tlie central nervous system, and the sympathetic neurones 
are homologues with the efferent and the afferent components of the 
other functional divisions ot‘ tlie periplieral nervous system. 
