But it is the particular nuances of St. Jerome in this regard that are the most directly relevant, to my mind, to the tacit meaning of Leonardo’s marveling remark. «But the organ is the body of man», says St. Jerome (in his Commentary on Psalm 136/137, Super flumina Babylonis). «As the organ is composed of many pipes, but brings forth melos through modulation, so we have our organ in touch [emphasis mine]: [13] through it, that is, through the works, music and song, we venerate God. Similarly, through hearing and smell and taste and sight, and with every faculty like one organ, in hymns and song we venerate God.» (Organum autem hominis corpus est. Sicut enim organum ex multis fistulis compositum est, unum autem modulation melos mittit, ita et organum nostrum habemus tacum: per ipsum, hoc est per opera, melos et canticum et hymnum referimus Deo. Similiter et per auditum, et per odoratum, et per gustum et per visum, et per has omnes virtutes quasi di uno organo hymnum et canticum referimus Domino). [14]

It is not unlikely that vague sedimentations of such allegories, and especially St. Jerome’s rendition, found their way into Leonardo’s hand-dissection page in question; for they are grounded in age-old percepts of the anatomical body as a reflection of the musical order of the universe. In his Neo-Platonist youth, Leonardo himself had already assimilated the non-material and incorruptible soul that dwells in the perishable, living body, to the air that blows in the pipes of the organ (Ms. Trivulzianus, 40v, c.1480). [15] Bar the claim for the eternity of the soul, which he was to abandon later, the anatomical note in question reflects a similar climate of ideas. It implies that the organ, and the human organ that mirrors it, are fraught with religious and metaphysical symbolism. Through the opera of «song and hymn», the anatomical intelligence of the hand that generates musical sound asserts the wisdom of the micro-macrocosmic body, its quintessential nature as music.

To a large extent, this orientation has privileged the pulmonary, cardiac, and blood systems that are responsible for breathing, transforming and diffusing the pneumatic (‹spiritual›) particles in the body. They were thus assumed to have a special affinity with the musical world-order. [16] Leonardo's cardiology demonstrates that he was indeed prejudiced by this notional background, and let it interfere with his investigations of the rhythm of the pulse. [17] But, that the anatomist-musician has integrated the hand into this convention was a pivotal, innovative move. In fact, in doing so he superimposed the reality of music-making onto the abstract allegory of the musical body.