Mix the baking soda and the vinegar separately into the milk. Combine dry ingredients, including the raisins and nuts, and add molasses and shortening. Add the milk mixture to the dry ingredients. Stir until well blended. Pour into 2 well-greased, medium-size loaf pans. Bake at 350 degrees F for 45 minutes or until done. Remove from pans and let cool on rack.