Leonardo may have been in the competition there and then, but the means for executing the monument do not seem to have been at once forthcoming.  It was not perhaps until some years later that Leonardo in a letter to the Duke (No. 719) reminded him of the project for the monument.  Then, after he had obeyed a summons to Milan, the plan seems to have been so far modified, perhaps in consequence of a remonstrance on the part of the artist, that a pacing horse was substituted for one galloping, and it may have been at the same time that the colossal dimensions of the statue were first decided on.  The designs given on Pl.  LXX, LXXI, LXXII, 2 and 3, LXXIII and LXXIV and on pp. 4 and 24, as well as three sketches on Pl.  LXIX may be studied with reference to the project in its new form, though it is hardly possible to believe that in either of these we see the design as it was actually carried out.  It is probable that in Milan Leonardo worked less on drawings, than in making small models of wax and clay as preparatory to his larger model.  Among the drawings enumerated above, one in black chalk, Pl.  LXXIII—­the upper sketch on the right hand side, reminds us strongly of the antique statue of Marcus Aurelius.  If, as it would seem, Leonardo had not until then visited Rome, he might easily have known this statue from drawings by his former master and friend Verrocchio, for Verrocchio had been in Rome for a long time between 1470 and 1480.  In 1473 Pope Sixtus IV had this antique equestrian statue restored and placed on a new pedestal in front of the church of San Giovanni in Luterano.  Leonardo, although he was painting independently as early as in 1472 is still spoken of as working in Verrocchio’s studio in 1477.  Two years later the Venetian senate decided on erecting an equestrian statue to Colleoni; and as Verrocchio, to whom the work was entrusted, did not at once move from Florence to Venice—­where he died in 1488 before the casting was completed—­but on the contrary remained in Florence for some years, perhaps even till 1485, Leonardo probably had the opportunity of seeing all his designs for the equestrian statue at Venice and the red chalk drawing on Pl.  LXXIV may be a reminiscence of it.

The pen and ink drawing on Pl.  LXXII, No. 3, reminds us of Donatello’s statue of Gattamelata at Padua.  However it does not appear that Leonardo was ever at Padua before 1499, but we may conclude that he took a special interest in this early bronze statue and the reports he could procure of it, form an incidental remark which is to be found in C. A. 145a; 432a, and which will be given in Vol.  II under Ricordi or Memoranda.  Among the studies—­in the widest sense of the word—­made in preparation statue we may include the Anatomy of the Horse which Lomazzo and Vas mention; the most important parts of this work still exist in the Queen’s Li Windsor.  It was beyond a doubt compiled by Leonardo when at Milan; only interesting records to be found among these designs are reproduced in Nos. 716a but it must be pointed out that out of 40 sheets of studies of the movements of the belonging to that treatise, a horse in full gallop occurs but once.