more about the implications of their work

These scientists describe their treatment as a vaccine using a bacteria-free solution. The obvious conclusion is
that they must have made an agent that involved no recognizable bacteria – but, in the light of current insights,
must have contained bacterial DNA in some form or other. One hundred years later, we know that colitis ulcerosa
is not caused by a virus, so the effectiveness of the inoculation cannot be attributed to an accidentally introduced virus.