Joseph Lister in Edinburgh Medical Journal 1876, vol. xxii,
pp. 280-284
"In investigating nature you will do well to bear ever in mind that in
every question there is the truth, whatever our notions may be. This
seems, perhaps, a very simple consideration, yet it is strange how
often it seems to be disregarded. I remember at an early period of my
own life showing to a man of high reputation as a teacher some
matters which I happened to have observed. And I was very much struck
and grieved to find that, while all the facts lay equally clear before
him, those only which squared with his previous theories seemed to
affect his organs of vision."
http://www.foundersofscience.net/lister.htm
http://web.ukonline.co.uk/b.gardner/Lister.html
http://en.wikipedia.org/wiki/Joseph_Lister

"...Semmelweis' superior, placed little stock in Semmelweis' doctrine,
belittled his work despite the evidence before them, thus diminishing
its impact..."
"...It required the passing of the old guard to fully accept the
doctrine of Semmelweis, namely the requirement for asepsis..."
Read of Semmelweis' discovery in his own words...
"Semmelweis, His Life and his Doctrine", W.J. Sinclair,
Manchester University Press,1909, p. 48-51
http://www.foundersofscience.net/semmelweis.htm
http://en.wikipedia.org/wiki/Ignaz_Semmelweis