Mix and sift dry ingredients. Cut in shortening with two knives or pastry blender. Stir lemon juice into milk and add quickly to flour mixture, using only enough to make a soft dough. Knead slightly on lightly floured board. Roll 1/2 inch thick and cut with floured cutter. Place on ungreased baking sheet and bake in very hot over, 450 degrees F 15 minutes.