250 ALBERT KUNTZ 



DISCUSSION AND CONCLUSIONS 



According to the observations set forth in the preceding pages, 

 the cranial sympathetic gangUa bear the same genetic relationships 

 to the cerebro-spinal nervous system, in all the classes of verte- 

 brates, as do the ganglia of the other parts of the sympathetic 

 nervous system, i.e., they arise from cells which have their origin 

 in the cerebro-spinal ganglia and the wall of the neural tube and 

 advance peripherally along sensory and motor nerve-roots respec- 

 tively. Not all the nervous elements taking part in the develop- 

 ment of the sympathetic ganglia actually migrate as such from 

 the cerebro-spinal ganglia or the neural tube; many of them 

 arise by the mitotic division of cells which have advanced periph- 

 erally from the cerebro-spinal nervous system. 



The character and the destiny of the cells which become sepa- 

 rated from the cerebro-spinal nervous system and advance periph- 

 erally along the cranial and spinal nerves have been discussed by 

 the writer in earlier papers and will, therefore, not be considered 

 in detail at this time. The majority of these elements are cells 

 of the 'indifferent' type, many of which retain the capacity for 

 cell division after they have become separated from the cerebro- 

 spinal ganglia or the neural tube. Consequently, mitotic figures 

 may be frequently observed along the paths of migration and in 

 the peripheral ganglia. Such mitotic division of nervous elements 

 in the paths of peripheral nerves and the primordia of peripheral 

 ganglia probably occurs less frequently in embryos of the lower 

 than in embryos of the higher vertebrates. Neither do all the 

 elements arising in this manner take part in the development of 

 sympathetic ganglia. Many of them obviously become differ- 

 entiated into cells of the neurilemma. 



The distribution and the relative degree of development of 

 the cranial sympathetic ganglia varies greatly in the several 

 classes of vertebrates. The degree of development of the several 

 cranial sympathetic ganglia is obviously correlated with the de- 

 mands of the functions of the structures innervated by the sym- 

 pathetic nerves associated with them. 



