LETTERS TO BROTHER JOHN. 61 



sesses striking marks of difference from all other 

 nerves : it is called " the great sympathetic pair." 

 I should have observed, that all the nerves are sent 

 off from the brain and spinal marrow in pairs. 

 This pair of nerves has given origin to endless dis- 

 cussions; some asserting that it arises from the 

 brain ; others, that it does not ; some, that it has 

 one office, some another. Fyfe says, " It is either 

 formed originally by the reflected branch from the 

 second of the fifth pair ; and by one or two, and 

 sometimes three, small filaments, sent down from 

 the sixth pair, whilst in the cavernous sinus : or, 

 according to the opinion of some authors, the sym- 

 pathetic sends off these small nerves to join the 

 fifth and sixth pairs." 



Mr. Green says, " This nerve is so essentially 

 distinguished from the other nerves of the body, 

 that it may be described separately, or as a separate 

 system of nerves." 



" It consists," he says, " of a considerable num- 

 ber of ganglia (hardish knobs), of which the num- 

 ber and size differ, not only in different individuals, 

 but in the same individual, on the two sides of 

 the body ; and of branches, which in part connect 

 these ganglia, or form junctions with the other 

 nerves ; and are in part distributed to the internal 



