214 ALBERT KUNTZ 



sense of confirmatory evidence, he set up the hypothesis that the 

 peripheral sympathetic plexuses arise as cellular offshoots from the 

 cerebro-spinal ganglia. 



Onodi ('86) finally established the cerebro-spinal origin of the 

 sympathetic trunks and the prevertebral plexuses for all verte- 

 brates. He believed that the cells at the distal ends of the spinal 

 ganglia are forced to advance farther peripherally by the pressure 

 exerted by the newly formed elements back of them. He could 

 not, however, derive the sympathetic trunks and the peripheral 

 sympathetic plexuses from the same source because he found no 

 cellular connections between these two complexes. He believed 

 it necessary, therefore, to cling to the doctrine of Remak with 

 regard to the peripheral sympathetic plexuses, and derive them 

 from the mesoderm. 



His ('90) introduced a new factor in the development of the 

 sympathetic nervous system. In a human embryo 6.9 mm. in 

 length, he observed cells migrating from the spinal ganglia. These 

 he described as germinal cells which break through the motor 

 roots of the spinal nerves and migrate in swarms toward the future 

 location of the sympathetic trunks. 



Pushing on the way indicated by his father, His, Jr., ('91) 

 traced the origin of the entire sympathetic system to the spinal 

 ganglia. He described cell-swarms in the chick similar to those 

 described by His, Sr., in the human embryo. These cell-swarms 

 become detached from the spinal ganglia, break through the motor 

 roots of the spinal nerves, and migrate toward the dorso-lateral 

 surfaces of the aorta, where they become aggregated into cell- 

 groups which constitute the anlagen of the sympathetic trunks. 



From these aggregates, cells proceed round the aorta until the 

 latter is surrounded ventrally by a complete ring of sympathetic 

 cells. This ring gives rise to new cell-swarms which migrate farther 

 peripheral^ and become the anlagen of the peripheral sympathetic 

 plexuses, including the sympathetic plexuses in the walls of the 

 digestive tube and the sympathetic components related to the vagi. 



In his later researches on embryos of the chick, His, Jr., ('97) 

 found that the earliest anlagen of the sympathetic system arise 

 about the beginning of the fourth day of incubation as a pair of 

 longitudinal cell-columns lying along the sides of the dorsal sur- 



