When the long axis of the child's body corresponds with that of the uterus, the child (provided the passages are normal) can be born in that position: it matters little, as far as the labour is concerned, which extremity of the child presents, so long as this is the case; but where the long axis of its body does not correspond with that of the uterus, the child must evidently lie more or less across, and will present with the arm or shoulder, a position in which it cannot be born. In stating this, we wish it to be understood, that we merely refer to the full grown living foetus, and not to one which is premature, or which has been some time dead in the uterus, as these follow no rule whatever, hence the positions of the child at the commencement of labour resolve themselves into two divisions, viz. where the median line of the child's body is parallel with that of the uterus, and where it is not; the first we shall call _natural_, the second _faulty_, presentations of the child. A description of the natural presentations will form the contents of the present chapter. The reader will almost anticipate us when we state, that the natural presentations consist of two classes, those where the cephalic, and those where the pelvic end of the child presents; in the first case, it will be a presentation of the cranium or of the face; in the second, of the nates, knees, or feet.[77] _Cranial presentations._ The presentation of the cranium, (or _vertex_, as it has been improperly called,) is of by far the most frequent occurrence; thus, for instance, of 4042 children which were born in the lying-in hospital, at Heidelberg, 3834 presented with the head; of these the 3795 with the cranium, and 39 with the face: in either case, whether it be a presentation of the cranium or of the face, it will be either with the right or the left side more or less foremost; the former, from its greater frequency, has been called the first position of the cranium or face, the latter the second position.