In his introduction he quotes Weiss:
"The commonest mistakes are in the omission of letters, syllables, words, and clauses in cases where the like or same followed, and the eye of the copyist wandered from one to the other by homoioteleuton [i.e., in consequence of the sameness of endings]. The instances in which letters or syllables were doubled are much less frequent. .." (Weiss, Introduction to the NT, Amer. ed. Vol ii, pp. 405-406)After a concise but excellent discussion, Whitney moves on to examples of singular (as known at that time) readings of the major Uncial MSS:
Mark 1:32-34 - 'They brought unto him all that were sick
[and them that were possessed with devils.
And all the city was gathered together at the
door. And he healed many that were sick]with divers diseases.'
Mark 6:34 - 'because they were [as sheep] not having a shepherd.'οψιας δε γενομενης οτε εδυ ο ηλιος εφερονπρος αυτον παντας τους κακως εχονταςκαι τους δαιμονιζομενους 33 και η πολιςολη επισυνηγμενη ην προς την θυρανκαιεθεραπευσεν πολλους κακως εχονταςποικιλαις νοσοις και δαιμονια πολλα εξε-βαλεν και ουκ ηφιεν λαλειν τα δαιμονιαοτι ηδεισαν αυτον ...
Mark 9:9 - 'he charged them that they should tell no one what they had seen, [unless] after the Son of man had risen from the dead.'
Mark 10:19 - "Thou knowest the commandments, [do not commit adultery],
Do not kill, do not steal, " etc.
Mark 11:2 - "Go your way into the village [that is over against you;] and..."
Mark 14:16 - 'And the disciples went forth [and came] into the city...'
Mark 15:47-16:1 - 'And Mary the Magdalene and Mary
[the mother of Joses beheld where he was laid. And when
the Sabbath was past, Mary the Magdalene and Mary]
the mother of James, and Salome, brought spices.'...
Even if some cases have been the result of copying the errors of a previous copyist, or an intermediary copy (now lost), as would often happen, the many examples give pause and indicate caution in taking any omission with such features as original simply because it is an old reading.