IV. TRANSMISSION OF THE TEXT
No book of ancient times has come down to us exactly as it left the hands of its author--all have been in some way altered. The material conditions under which a book was spread before the invention of printing (1440), the little care of the copyists, correctors, and glossators for the text, so different from the desire of accuracy exhibited to-day, explain sufficiently the divergences we find between various manuscripts of the same work. To these causes may be added, in regard to the Scriptures, exegetical difficulties and dogmatical controversies. To exempt the scared writings from ordinary conditions a very special providence would have been necessary, and it has not been the will of God to exercise this providence. More than 150,000 different readings have been found in the older witnesses to the text of the New Testament--which in itself is a proof that Scriptures are not the only, nor the principal, means of revelation.
Who said that ?
Christians them selfs
Here the Source :
http://www.newadvent.org/cathen/14530a.htm#IV