The theme of the Virgin breast-feeding, Virgo lactans, represented as early as the 2nd century in the Catacombs of Priscilla, is the oldest in Marian iconography. Its literary source, Lucas 2, 27, is reiterated by Saint Augustine (“Intumescunt ubera Virginis et intact manent genitalia Matris”), but its origins are pre-Christian and go back to the Egyptian group of Isis breast-feeding Horus, later Christianized through Coptic art (Réau 1957, II, p. 96).
The work features a dark background, skillfully bringing out figures impregnated with Leonardian sfumato, and the scene shows characteristic components of Leonardo da Vinci’s Virgins. The position of the Child Jesus, for example, is inverted in relation to that of the Child in the so-called Hermitage Madonna Litta, usually dated from about 1490 –whereas the fantastic view seen through the window, with its mountains and extraterrestrial atmosphere, shows pure, orthodox Leonardian influence. More often, Giampietrino uses well-established Quattrocento motifs: the tile floor that precisely scans the successive planes, the win- dow that lets in the outside in counterpoint to the spatial cubes and the curtain with its diverse scenic symbolism. The vine-leaf decorated column supposedly alludes to the mystery of the Eucharist and, like the cross embraced by Saint John the Baptist, mystically augurs the sacrifice.
Particularly notable is the fact that the figure and the position of the Virgin are practically identical to a work on the same subject in Highnam Court, Gloucester, England, which Ottino della Chiesa (1967, p. 113) attributed hypothetically to Giampietrino. According to Suida (in Ottino della Chiesa), the work, etched in 1691, may derive from a lost Leonardo da Vinci model, dating from about 1490. The Masp’s work –The Virgin Nursing the Child with the Infant St. John the Baptist in Adoration–, because of its more distended composition and narrative characterization of the figures, in addition to not being considered a Leonardo da Vinci derivation in the strict sense, should be given a later date, possibly between 1500 and 1520.
— Unknown authorship, 1998