Object TRACK_PROBE_X(X,K, FIBRE1,FIBRE2,NODE1,NODE2)

• X is an array of initial conditions and final upon return.
• K is an INTERNAL_STATE.
• FIBRE1,FIBRE2,NODE1,NODE2 are all obejcts: FIBREs and INTEGRATION_NODEs.
• Here one specifies the initial FIBRE in FIBRE1 and the program tracks to the front of FIBRE2
• FIBRE2 is optional. If not there, tracking continues all the way to the front of FIBRE1 or to a terminated FIBRE pointer.
• Here one specifies the initial INTEGRATION_NODE in NODE1 and the program tracks to the front of NODE2
• NODE2 is optional. If not there, tracking continues all the way to the front of NODE1 or to a terminated NODE pointer.

Nodes and Fibres are mixable. For example, TRACK_PROBE_X(X,K, FIBRE1=p1,NODE2=n2) is acceptable.