Among the conditions that the Mishnah (56b) lists as not rendering a bird a terefah, is when its innards are protruding from the body but remain uninjured. In the Gemara Rabbi Shmuel bar Rav Yitzhak adds that this is true only if the intestines did not become twisted, but if they became twisted the bird would be rendered a terefah. The suggested source for this is a passage in Sefer (32:6), where we learn that “God…made you He established you,” which is understood to mean that the internal organs sit in a certain fashion, and if they are improperly replaced the person cannot live. Although this particular situation is not enumerated in the Mishnah regarding birds, the Gemara applies this concept to all other animals, as well as humans. Tosafot explains that this is included in the Mishnah since twisted intestines are destined to become pierced or torn.
In response to this teaching, the Gemara relates the following story:
A Romanonce saw a man fall from the roof to the ground so that his belly burst open and his entrails protruded. The Roman thereupon brought the son of the victim and by means of an optical illusion made out as if he slaughtered him in the presence of the father.The father became faint, sighed deeply and drew in his entrails; whereupon his belly was immediately stitched up.
Rashi explains that the Roman was aware of the above teaching and feared that if he were to touch the man’s intestines and attempt to replace them in his body, it was likely that he would be the cause of the man’s death. The purpose of this trick was to horrify the man so terribly as to cause him to take in a deep breath and draw in his entrails, thus they would be replaced without the aid of the hand of man.