"Under Texas law, abortion is permitted only “for the purpose of saving the life of the mother.” If, following the performance of an abortion, under this law, a physician is brought to trial and the jury disagrees with the physician’s interpretation of the meaning of these quoted words, the physician is liable to imprisonment for from two to five years in the penitentiary. This Court has declared that “a statute which either forbids or requires the doing of an act in terms so vague that men of common intelligence must necessarily guess at its meaning and differ as to its application, violates the first essential of due process of law.” Under this standard the statute must fall, because amici respectfully submit that neither they, nor Dr. Hallford nor any other similarly situated physician receive proper notice from the statute of what acts and consultations in their daily practice of medicine will subject them to criminal liability."