The evidence for the continuing accretion of gas by the Milky Way involves high-velocity clouds, or HVCs--mysterious clumps of hydrogen, moving rapidly through the outer regions of the galaxy.
Chemicals can not move through our galaxies outer reaches.
( z1 possible :polarity - :ARG1 ( z2 move :ARG1 ( z3 chemical ) :ARG2 ( z4 reach :mod ( z5 outer ) :part-of ( z6 galaxy :poss ( z7 we ) ) ) ) )