In this position there is no rotation at all, the back of the child being turned full to the back of the mother, and the whole body, and head, being expelled in that position. In general there is no particular difficulty from this position, but on the contrary it is thought by some to be rather favorable than otherwise. The longest diameter of the fœtal pelvis, and shoulders, are adapted to the longest diameter of the mother's pelvis, at the upper strait, and easily pass it. They will also generally pass the external opening in the same direction, unless it be very unyielding, or the child very large; and if they pass the head usually follows, because the parts have been so much dilated by the passage of the body that they offer but little resistance. GENERAL REMARKS ON THE PRESENTATION OF THE LOWER EXTREMITIES. As a general rule delivery by the breech, or by any other position of the lower extremities, is less favorable than by the head. The labor is usually longer, more painful, and more exhausting; still however, it is generally spontaneous, and not necessarily dangerous to the mother. To the child, on the contrary, it is dangerous, on many accounts. It appears, from the observations of M. P. Dubois, that in this presentation _one child is lost out of every twelve_, while only one out of _fifty_ is lost in head presentations! The chief cause for this greater mortality appears to be _the compression of the umbilical cord_, which is greater, and lasts much longer, than when the head presents, as will be evident on examining the circumstances under which delivery is effected in each case. When the head presents it passes, and also the shoulders, before the umbilicus is reached; the mother's organs are therefore much dilated, and only the smallest parts of the fœtus are left, when the cord is engaged in the passage; it cannot therefore be much compressed, nor for any long time, because the labor is then soon over. When the lower extremities present this is not the case, the _smallest_ parts then pass before the umbilicus is reached, so that the cord has to pass along with the head and shoulders, which are both the largest and the longest in being delivered. This compression of the cord stops the circulation of blood between the fœtus and the Placenta, as will be evident on referring to the description formerly given of _Fœtal nutrition_; and the stopping of this circulation is as fatal, to it, as stopping the breath is to an adult. When the breech presents altogether, there is not so much danger as with the feet, or knees, because it is large, and in its passage dilates the parts so much that the rest of the body, and the head, follow more quickly. There is, of course, no danger till after the hips have passed, because the cord is not reached before; but the delivery should be completed as soon after they are born as possible, for every minute's delay makes the chances for the child's life so much less. CHAPTER XIII.