In irregular presentations, as of the arms for instance, or of one leg, or an arm and leg, it is only necessary to carefully feel them, so as to ascertain their form, and the relation of their parts. Thus the fingers can be distinguished from the toes, and the feet from the hands, particularly if the ankle can be felt. The accoucheur should ascertain the particular presentation _as early as possible_, because he may sometimes be of service in correcting an unfavorable one, if he is certain of it in time, and knows what he is about. He should not however, use any degree of force to ascertain it, in case he cannot do so without, but wait till the conditions are more favorable. Neither should he, with the same object, rupture the membranes too soon, for he may thereby cause considerable delay and difficulty, without any good to counterbalance it. All the above-named presentations may, and usually do, terminate spontaneously, except those of the trunk, and even they do occasionally, though more frequently they require assistance. _Relative frequency of the different presentations._--The most favorable presentations, and positions also, are always the most frequent, while the unfavorable ones are but seldom met with. According to Madame Lachapelle, in _fifteen thousand six hundred and fifty-two labors_ there are about _fourteen thousand seven hundred and forty-nine_ presentations of the head and face; about _five hundred and eighty-six_ of the breech, knees, and feet; and only about _sixty-eight_ of the trunk, or shoulders. _Positions._--The position is generally of but little consequence, because in all the favorable presentations spontaneous delivery occurs in every position alike, and in the unfavorable presentations the same assistance is required in one position as in another. In some cases an unfavorable position of the head may be changed however, to a better one; and therefore, so far as the head is concerned, the positions are worth ascertaining. The mode of determining the position is by feeling for the _sutures_ and _fontanelles_, described in Chapter VIII; and this cannot be usually done till after the membranes are broken, when the head can be distinctly touched. By referring to Plate XXIV, the shape and position of the Fontanelles will be seen, and if the head be supposed placed with the top downwards, and the back of it to the mother's left side, they may be readily found with the finger.