#11422 Fix embedded definition of CNS to exclude spinal nerves

[Chris Mungall]

Not that it matters much but the highlighted section is wrong:

def: "The process in which the anatomical structure of the central nervous system is generated and organized. The central nervous system is the core nervous system that serves an integrating and coordinating function. In vertebrates it consists of the brain, spinal cord ***and spinal nerves***. In those invertebrates with a central nervous system it typically consists of a brain, cerebral ganglia and a nerve cord." [GOC:cls, GOC:dgh, GOC:dph, GOC:jid, GOC:mtg_15jun06, GO_REF:0000021, ISBN:0582227089]

spinal nerves are in the PNS.

Mistake repeated here:

 GO:0007417 ! central nervous system development
 GO:0021551 ! central nervous system morphogenesis
 GO:0021556 ! central nervous system formation
 GO:0021597 ! central nervous system structural organization
 GO:0021626 ! central nervous system maturation

Of course, CNS is hard to define for all animals, see section 21 here http://www.frontiersinzoology.com/content/7/1/29

Taxon-specific enumerations are probably fine. For vertebrates CNS = B+SC

For inverts, I suspect it's a bit more complex than the existing enumeration of brain/CG + NC