Pulling and leading yes; but not riding - מושך ומנהיג אין אבל רכוב לא
Summary:
The need to teach that one קנין is not מבטל another is only where the superior קנין contains all the elements of the other קנין plus an additional advantage; however it if does not contain all the elements of the inferior קנין, then it is obvious that it cannot be מבטל the inferior קנין.
And the rider should also acquire the reins - ונקני נמי רכוב במוסירה
Summary:
One cannot be קונה מטלטלין by merely holding them; a משיכה or הגבהה is required. If one is מנהיג ברגליו he should be קונה the מוסירה if we assume that by משוך בהמה זו וקני כלים שעליה he acquires the כלים.
And neither acquires the rest - והשאר לא קנה לא זה ולא זה
Summary:
The רכוב cannot acquire the מוסירה since the תפיס has no intention of being מקנה to him the מוסירה (especially since he cannot acquire it for himself).
Since he can snatch it and bring it to him - הואיל ויכול לנתקו ולהביאו אצלו
Summary:
A קנין הגבהה is effective if it cannot fall to the ground, unless it was raised higher than its original position. Alternately it is effective even if it will fall down as long as the קונה is holding it partly raised.