"Aha! I know what to do!" the woman exclaims. She then gets to work, stripping what little clothing you were given off, and picking up a syringe. She then forces some pills down your throat, soon causing a painful boner. Next she sticks the needle directly into your hard cock. Oddly enough, it brings no pain. Next comes another syring, this one with a white liquid.
"There. Now I've injected you with horse DNA, specifcally the penis strand. The white liquid was to solidify it into every cell in your body, making it as if you were always like this. It also made the udder permanent. And now that it's part of your natural genome, it can be passed onto children."
She then surprised you with another syringe, with a clear liquid. It is inserted directly into your chest.
"This will cause cells to divide much quicker, allowing your changes to occur quickly. It won't wear off until I inject you with a finallizing syrum, so future changes I may or may not decide to make will also occur quicker."
Soon your cock starts throbbing, feeling painful yet pleasurable. The first change to come is the size of your penis, soon swelling to massive proportions. After it got to a point where it would seem large on a human, it continues to grow. The boner you had has stopped, and you know that if you were to be excited again the new penis would be even larger. When it stops growing, it's a foot and a half long and 4 inches thick, flacid. Your testicles are the sixe of oranges now. Next comes the head, which changes shape to become much more equine. After that, your penis then starts to grow a chestnut colored hairy sheath, covering most of the penis. Hair of the same color covers your ballsack, and your pubes change to be that same color.
"Well, that went well. Though I am a bit surprised and a little disappointed that the hair only went to your pubes and didn't spread further. Now, what next...?'