Complex sentence: Steiner gave several series of lectures to physicians and medical students; out of this grew a complementary medical movement which now includes hundreds of M.D.s, chiefly in Europe and North America, and which has its own clinics, hospitals, and medical schools.
Split into simpler sentences: Steiner gave several series of lectures to physicians and medical students. Out of those grew a complementary medical movement, which now includes hundreds of M.D.s, chiefly in Europe and North America, and has its own clinics, hospitals, and medical schools.