Her mouth

The scientist bring a small medecine stick and put it in her mouth. He go deeper every seconds. But suddenly, something start to pull him in. He let go of the stick and notice the situation. The pull caused by whatever's inside the intern manage to fit his whole hand along with his wrist in her mouth. Surprised at this, he's curious at how much can she fit in her mouth now. This need to be experiment on. But first, he should pull his arm off her mouth.