Excerpt pertaining to errors in manuscripts due to medieval scribes.

From page 51 of Foundations of Modern Science in the Middle Ages, by Edward Grant.

"Before the advent of printing in the middle of the fifteenth century, treatises in medieval science and natural philosophy depended for their existence on manuscript copies. As a consequence, they were subject to all the vagaries and uncertainties of any system that must rely on a scribe or copyist to produce one or more copies from an exemplar or to record a lecture as it was given. Medieval Latin texts were subject to more than the ordinary scribal vicissitudes - errors of commission and omission - because medieval copyists had developed an elaborate system of abbreviations that served to speed the process of copying and also tended to save paper."