In Cranium presentations also, the back of the head is not merely on the right or left side, but may be at two different points on each side. It may be either nearest to the Sacrum (posterior), or nearest to the pubes (anterior), but still against the Ilium; it is therefore called a _right or left anterior_, _or posterior_, _occipito iliac position_, as the case may be. Sometimes also, the occiput lodges immediately on the pubis, instead of going to either side, and that is called an _occipito pubic position_; at other times, on the contrary, it is placed against the Sacrum, instead of being on either side, and that is called an _occipito sacral position_. In presentations of the head therefore, we may reckon _six_ positions--the right and left anterior and posterior occipito iliac, and the pubic and sacral. In presentations of the face the same; they being _mento_ iliac and so on, instead of occipito. In presentations of the lower extremities also the same, excepting that they are _sacro_ iliac and so on, instead of occipito. In presentations of the trunk we have but two positions for each side, the right and left cephalo iliac; according as the head is on the right or left side of the mother's body. The child always lying, in presentations of the trunk, crosswise--the feet on one side and the head on the other. Most authors enumerate many more presentations and positions, but they are of little practical utility. When the head presents, for instance, the delivery takes place in nearly the same manner, let it be in what position it may. And in presentations of the face, or of the lower extremities, the particular position is of little consequence, the delivery being usually effected much the same in them all. Some of the positions are, it is true, much more favorable than others, but a spontaneous delivery, generally speaking, occurs in all of them, when the head, face, or lower extremities presents. Very frequently indeed, the less favorable positions are changed to the more favorable ones, and the worst seldom do more than impede delivery for a time, unless there be some malformation, or loss of power. I therefore refer to them more for convenience in future explanations, and to enable my readers to know what is meant by them, when they read other books; not because they are really necessary to be understood, or of any great practical use. The celebrated Baudelocque admitted _seventy-four positions_, and _twenty-two presentations_; and the number might be made still greater, if all the variations were to be enumerated. Such classifications however, are more ingenious than useful, and they are but little noticed even by medical men. I shall merely describe the mechanism of labor in the most frequent positions, in each presentation, because the others usually change into these; and even when they do not, the process of delivery is essentially the same, and also the mode of assisting it.