The last salient point in which the systems of these creatures
differed from ours was in what one might have thought a very trivial
particular.  Micro-organisms, which cause so much disease and pain on
earth, have either never appeared upon Mars or Martian sanitary
science eliminated them ages ago.  A hundred diseases, all the fevers
and contagions of human life, consumption, cancers, tumours and such
morbidities, never enter the scheme of their life.  And speaking of
the differences between the life on Mars and terrestrial life, I may
allude here to the curious suggestions of the red weed.