Note: If using the lamb's head, wash it, then soak it in cold water for 3 hours. Drain. Cut the head in half, using a sharp knife, and tie with a clean string. If using the lamb's feet and tripe, prepare as follows: If tripe is not parially cooked, cut open with a sharp knife and clean the inside thoroughly under running water. Put in a pan with cold salted water to cover and soak for 30 minutes, then drain and wash with cold water. Cut into small pieces and put in a large soup pot with the lamb's feet. cover with cold water, and simmer until tender, adding salt to taste during the last minutes of cooking. Cube the tripe, remove the meat of the feet from the bones, and add to the mageritsa at the same time as the cut-up intestines, adjusting the liquid by adding more water. Clean the intestines thoroughly by turning them inside out, using a long skewer or stick (this turning will be quicker if the intestines are first cut into 61 cm lengths), then wash under cold running water until clean. Rub the intestines with salt and the juice of half lemon, rinse again in cold water and drain. Braid the intestines or tie the ends together with clean string. Put in a large soup pot with the lamb's head, if using, and cove with cold water. Bring to a boil, then lower the heat, skim, and simmer for 30 minutes. Remove the intestines, drain them, and cut into 1 cm pieces with the scissors and set aside to add to the soup later. (Use the remaining portion of the head for another dish.) Bring the soup stock to a boil and add the scallions, parsley, dill, and celery leaves. Cut the heart, lungs, and liver into small bite-sized cubes, and add them to the soup, and simmer for 15 minutes. Add the rice, cut-up intestines, aniseed, salt and pepper to taste and continue simmering until the rice is tender, approximately 15 minutes, adding more water as needed and the brains during the last few minutes of cooking. Half an hour before serving, bring the soup to a boil, then remove from the heat and prepare the avgolemono: Beat the eggs for 2 minutes. Continue to beat, gradually add the remaining lemon juice. Then 1 to 2 cups of the hot soup by droplets, beating steadily, until all has been added. Add the avgolemono to the soup. Stir over minimum heat until thickened. Serve warm but avoid boiling the soup after adding the avgolemono. A richer Mageritsa can be made by sauteing the scallions in 3 tablespoons butter or oil before adding to the soup.