"Just a BIT more cow-like, I guess." Mary considers her options aloud, thumbing through the box's contents until she found the right one. She pulled it out and looked at it through the sunlight pouring in through the window.
Then she takes another sip, contemplating the bitter flavor in her mouth for a bit before swallowing it.
With a feeling like a surge of adrenaline, the potion gets to work, coursing its way through her veins. Short fur sprouts up over her steadily fattening body, white with black splotches. Her eyes darken to a brown so deep they seem solid black, with her face squaring away ever so slightly, her nose spreading to a snout. Her ears slowly migrate to the top of her head, lengthening and drooping down over the sides of her head.
She watches with awe as her hands and feet change noticeably. She finds herself forced onto her tip-toes as her feet become cloven hooves, and watches her fingers meld from four to two with a thick hooven fingernail on each.
She's almost surprised as her tail slaps idly against her leg, and is so busy watching this new appendage that she doesn't notice her breasts fade away as the udder takes over as her mammary glands.
"Wow," she says in a noticeably deeper voice, almost comical in its timbre, as if she was mocking someone. She licks her lips with a six-inch long tongue, feeling hungry. Her stomach has multiplied, so it requires a bit more food.
"Hurk," That's when she throws up last night's dinner, but keeps it in her mouth. She doesn't find anything odd in the fact that she begins to chew it with a steady side-to-side motion of her jaw. After all, cows chew cud, so it stands to reason that a humanoid cow would do the same.
She doesn't even think about milk production, which would be absurd. She can't produce milk unless she were to have a calf, which at this point would be pretty impossible.