15.4.12  SLICES 

          [SLICES [X|Y|Z] [FROM] v1 [[TO] v2]] [CYCLE[=ON|OFF]]
               or...
          [SLICE X|Y|Z=v1] [CYCLE[=ON|OFF]]

This plots or joins points sliced from mesh data.  This command is illegal
for normal data.  If v2 is omitted then v2=v1.  If  a  range  is  selected
then  all  slices within the range are histogrammed.  IF you set THREE=OFF
then the slices are histogrammed according to the first  X,Y,Z  Mentioned.
If  X is first then the slices are taken perpendicular to the X axis.  You
only need select X|Y|Z the first time you slice after a NEW FRAME command.