Pietro Stops Don Gianni’s Mare-Transformation Spell

Pietro Stops Don Gianni’s Mare-Transformation Spell is a comic episode in which a husband’s belief in magic brings him to the brink of surrendering his wife to a priest’s sexual deception. Dom Gianni di Barolo claims he can turn his mare into a woman and back again; when he stages the same transformation with Gemmata, Pietro’s protest at the crucial moment interrupts the performance. His intervention spoils the supposed spell, but not because he sees through the trick: he objects because he thinks the mare’s tail is being put on incorrectly.

Friendship and Unequal Hospitality

Dom Gianni di Barolo, a priest with a poor living in Barletta, supplements his income by trading goods at fairs throughout Apulia. On the road he becomes close friends with Pietro da Tresanti, another trader, who travels with an ass. They call one another gossip, a customary form of address expressing their friendship, and exchange hospitality. When Pietro visits Barletta, Dom Gianni lodges and entertains him; when Dom Gianni visits Tresanti, Pietro welcomes him as well as he can.

The difference in their circumstances shapes the episode. Pietro’s small house has only one poor bed, which he shares with Gemmata, while Dom Gianni must sleep on a truss of straw beside his mare in the stable. Gemmata knows that her husband’s friend has treated him generously in Barletta. More than once, she offers to spend the night at a neighbor’s home so Dom Gianni can share the bed with Pietro, but the priest refuses. His stated reason changes the meaning of that refusal: he says he can transform his mare into a handsome woman and lie with her, then turn her back into a mare whenever he chooses. The supposed marvel gives him a pretext to keep sleeping apart and hints at the deception he is preparing.

A Spell Pietro Believes

Gemmata takes Dom Gianni’s account seriously and tells Pietro about it. She urges her husband to learn the charm, reasoning that if he can turn her into a mare and use her sexually alongside the animals, they will gain two working beasts for the price of one. The proposal exposes how completely she and Pietro accept the priest’s premise: rather than challenge the idea that a person could be transformed, they consider its practical benefit to their poor household.

Pietro is not especially sharp-witted, and Gemmata’s suggestion persuades him. He repeatedly presses Dom Gianni to teach him the trick. The priest tries to dissuade him, but when that fails, he agrees to demonstrate it the following morning before daybreak. He warns that putting on the tail is the most difficult part. The warning makes the final stage of the performance seem like a technical problem, preparing Pietro to watch closely for a mistake rather than question whether any transformation is taking place.

The Interrupted Transformation

Before dawn, Pietro and Gemmata, who have scarcely slept in their impatience, wake Dom Gianni. He enters their small chamber in his shirt and tells them they must follow his instructions if the operation is to succeed. He gives Pietro a light to hold and insists that he remain silent, whatever he sees or hears, and pray that the tail sticks fast. The command creates the scene’s central tension: Pietro has promised to obey, but his close attention to the procedure makes him likely to intervene if it appears to go wrong.

Dom Gianni strips Gemmata and has her stand on all fours like a mare. Touching her in turn, he names her head, hair, arms, breasts, back, belly, hindquarters, thighs, and legs as parts of a mare. The mock ritual proceeds methodically, presenting each part of her body as though the transformation were being completed through spoken declarations and gestures. At the breast, his excitement betrays the sexual reality concealed by the language of magic. The performance reaches its climax when he takes a dibble, the planting tool, and uses it to enact the making of the tail.

Pietro has kept watch throughout, but at this last action he can no longer hold his tongue. He objects that he will not have a tail put there. Dom Gianni immediately blames him for breaking the silence he had demanded: the mare, he claims, was already made, and Pietro’s words have ruined the charm beyond repair. The excuse preserves the fiction just long enough to make Pietro, rather than the priest, seem responsible for the failed transformation. Pietro’s protest thus stops the sexual act from being completed, while leaving him ignorant of the priest’s actual purpose.

Consequences and Comic Reversal

Gemmata dresses, distressed that Pietro has spoiled what she believed might be useful to their household. She reproaches him for preventing her transformation and points out that a mare without a tail would make no sense. Pietro continues his old trade with his ass, and he never again asks Dom Gianni to perform the service. The scene ends not with discovery or punishment, but with the couple abandoning the impossible bargain and returning to their ordinary life.

The reversal depends on the difference between what Pietro thinks he is interrupting and what the audience can recognize in the staged rite. He believes the problem is a badly placed tail; his words prevent Dom Gianni from proceeding, but do not reveal that the spell is a sham. His naïveté both enables the priest’s deception and accidentally frustrates it. In the tale’s closing frame, the company laughs at the episode, which Dioneo’s listeners understand more fully than he intended. That response makes the gap between the innocent explanation and the sexual joke part of the ending: the supposed failure of magic is also the moment when the performance gives itself away.