Jake shrugged off his parents' warnings and shoved his head into the water. Lapping some of it up, until his thirst was sated, he got up, wiped his mouth and started walking home.
As Jake was walking along the trail back to his house, he felt a strange itching all over his body. Looking down at his arms, which were revealed due to the fact he was wearing a T-shirt, he saw brown hairs sprouting up all over them. Looking down at his legs, which were also revealed due to the fact that he was wearing shorts, he saw the same hairs.
Shrugging off the hairs, as he could always shave them off when he got home if his parents didn't like them, Jake went on his way.
As Jake reached a familiar landmark that let him know he was near his house, he was suddenly hit with a terrible earache. Reaching up to touch his ears, he felt them slowly triangulate and move to the top of his head.
This was only the first of his problems. As Jake felt his now triangular and furry ears, he noticed his hair growing longer. By the time it got down to his back, he realized that it didn't feel like his hair at all. It felt more like the mane of one of the horses that his family owned. "So that's it," Jake thought. "I'm turning into a horse." His ten year old brain really couldn't find anything wrong with this. For all he knew, this happened to everyone at his age.
Jake suddenly felt short of breath. Inhaling and exhaling rapidly, he noticed his chest slowly barrel out with new muscle and mass. Realizing what would happen next, Jake prepared himself as his shirt was ripped off, except for a few solitary pieces of fabric that still clung to his arms. Pulling these off with steadily stiffening fingernails, Jake looked down at his now massive muscular chest.
Feeling his shorts and underwear tightening around his legs, Jake managed to pull both of them off before they ripped off, and for good measure pulled off his shoes and socks. He looked down at his legs, seeing that they appeared longer, as well as muscular. Looking at his penis, Jake saw that it had now turned black and grown to a rather impressive size, and was just now finishing being cocooned in a furry sheath. Jake also noticed that his testicles had grown to about the size of grapefruits.
Knowing that only a few more changes remained, Jake was alerted to a tugging sensation above his butt. Looking back over his changing shoulders, Jake saw a tail sprout out of his tail bone. The fur on the tail felt like the fur on his mane, not like the fur on the rest of his body, which was soft and silky. Wondering why he was making such observations, Jake went back to staring at his hands and feet, which were just finishing forming into hooves.
After watching his new hooves form out of what were originally his finger and toe nails, Jake felt his head begin to change. His neck lengthened and his face pushed out into a muzzle. His eyes also changed, becoming big and brown. After these changes, Jake felt the force of gravity pushing his new bulk toward earth. Once he was forced down onto all fours, Jake somehow knew the changes were complete.
Not knowing anything better to do, Jake trotted off toward home. As he came within sight of the family home and stables, he began to think about what would become of him. He still had his human mind, so maybe he could try to communicate with his parents? Suddenly he remembered his father talking about purchasing a new colt to raise as a stallion to breed with the mares on his farm. New feelings and thoughts rushed over Jake, thoughts taboo to his human mind, as he wondered about what kind of life that would be