Two different opinions are brought regarding if and when one can use a non-Jew as a doctor. Rav Yehuda says only for one’s animals and Rabbi Yochanan says as long as it’s not a life-threatening disease. However, there are exceptions such as an expert doctor whose reputation is on the line, if the doctor takes money for it (as he/she wants to get paid), if it is one’s last chance and he/she will die anyway without the non-Jew intervening. What is the difference between heretics and non-Jews regarding these laws? One explanation of Rabbi Yochanan is that the criteria for determining if it is life-threatening is the same as for Shabbat (one can desecrate Shabbat for a life-threatening illness). The gemara tangents to Shabbat and from there to all sorts of remedies for various ailments.