McCreedy carefully folded his clothes and stood naked, shivering slightly in the drafty barn. At one level, he still couldn't believe he was doing this. He raised the two vials to his lips, and in quick succession drank about half of the "youth" vial and all but a few drops of the "boar."
The vials fell from McCreedy's hands as his fingers joined and hardened into cloven hooves. He pitched forward, and landed on his new front legs. At the same time he felt the aching bones and joints of old age replaced by a feeling of health and energy. His skin toughened, and sprouted reddish hairs. He felt his face pull forward, into a snout, and his new senses were bombarded by a thousand new smells.
One smell in particular, coming from the nearby pigpen. McCreedy the boar felt it charge him with a wave of sexual energy. He couldn't remember ever being this turned on as a human, in fact, at the moment he couldn't remember being a human. All of his energy was oriented to sex, as he trotted rapidly to the pig pen.
If a sow could grin, Mary would have had a big one plastered over her snout. The thought that she could bring a litter of piglets into the world made her feel fully a part of her wonderful new species. She presented her rear to the wonderful, virile young boar trotting into the pen.