On the whole presentations of the face are not particularly to be feared, as regards the mother. Some authors even consider them quite favorable, and reckon them only as varieties of the head presentation. Madame Lachapelle states as a principle, that face presentations should always be left to nature. And M. Chailly says he must admit that, in all positions of the face, the labor may terminate spontaneously, excepting when the chin passes behind, in which case it will be protracted, and most likely fatal to the child. The labor is generally a little longer, and more painful, owing to the face not being so perfectly adapted to the passage as the head is; but still it must be regarded as favorable to the mother, though assistance is oftener required than with the head. There is more or less danger to the child however, owing to the head being kept under pressure for an unusual time, which produces congestion. The neck is also forced against the pubic bone, as will be seen by Figs. 1 and 2, Plate XXXIV, and thus the jugular veins are compressed. If there be any delay, it is customary to observe the face closely, after the chin is born; and if it appears from any indications that congestion is taking place, assistance is rendered at once. The face will sometimes become so tumefied, and engorged with blood, from this prolonged pressure, that it will not appear natural till several days after birth. Probably about one child is lost in ten or twelve deliveries in these cases; and if the chin pass behind its death is almost certain. It was formerly the practice to endeavor to turn the face upwards, when at the superior strait, and so change the presentation to one of the head. This however, is now abandoned, because the attempt is seldom successful, and does not materially improve the condition of things, besides being painful to the mother. The only extra danger with the face presenting is to the child, and this is not removed by the operation; to the mother the face is nearly as favorable as the cranium. In regard to the frequency of face presentations, we find that Madame Lachapelle met with but _seventy-two_ cases in _fifteen thousand six hundred and fifty-two deliveries_. CHAPTER XIV. MECHANISM OF DELIVERY IN PRESENTATIONS OF THE TRUNK. It has already been stated that in presentations of the Trunk it is nearly always the right or left shoulder which occupies the passage. It is stated, by some authors, that they have felt the back, and abdomen, but others think they were mistaken; and most certainly such positions are extremely rare, if they actually do ever exist. There are two presentations of the Trunk, determined by the side on which the fœtus lies, and denominated accordingly _right_ or _left lateral presentations_.