SYMPATHETIC NERVOUS SYSTEM IN MAN 205 



Hoffmann ('00), who made careful observations on Elasmo- 

 branch embryos, was among the earhest investigators who con- 

 cluded that some of the sympathetic elements are derived from 

 the neural tube via the ventral roots of the spinal nerves. Har- 

 rison ('01) was led to the same conclusion by his observations on 

 embryos of the salmon. This conclusion was further supported 

 by Harrison's ('04) experimental observations on amphibian 

 larvae. Neumayer ('06), though not an advocate of the migra- 

 tion theory, inferred from his observations on embryos of Lacerta 

 and the chick that the sympathetic primordia are derived both 

 from cells in the dorsal and the ventral nerve roots. Carpenter 

 ('06) recognized the cells which migrate from the wall of the mid- 

 brain along the oculomotor and the abducent nerves, in embryos 

 of the chick, as the 'indifferent' cells of Schaper, i.e., cells which 

 have the capacity either to develop into neurones or supporting 

 elements. He further observed that some of the cells of this 

 type associated with the oculomotor nerve become incorporated 

 in the ciliary ganglion. 



Froriep ('07) was perhaps the first investigator who vigor- 

 ously supported the theory that cells of medullary origin which 

 advance peripherally along the motor roots of the cerebrospinal 

 nerves play an important part in the development of the sympa- 

 thetic nervous system. Indeed, he concluded that all sympa- 

 thetic neurones are derived from cells which have their origin 

 in the ventral half of the neural tube. His observations were 

 based on embryos of Torpedo and the rabbit. Cajal ('08) drew 

 essentially the same conclusion from his observations on embryos 

 of the chick. By the aid of his own specialized technique he 

 recognized elements in the motor roots of the spinal and certain 

 of the cranial nerves as nerve cells in the bipolar phase. His ob- 

 servations show clearly that at least some of the cells which 

 migrate from the medullary tube into the motor nerve roots 

 become differentiated into neurones. 



As far as the writer has been able to ascertain, Froriep and 

 Cajal are the only investigators who have supported the theory 

 that the sympathetic neurones are derived exclusively from cells 

 which have their origin in the ventral half of the neural tube and 



