_First cranial position._ It will be recollected we have stated, that the os uteri at the end of pregnancy is turned obliquely backwards, corresponding to the upper part of the hollow of the sacrum. If we examine during the first stage of labour, when it is just dilated sufficiently to allow the finger to pass, we shall feel the sagittal suture of the head running across it, dividing it into two unequal portions, the os uteri itself corresponding nearly to the middle of this suture. If the os uteri be sufficiently dilated to let us trace its course, we shall find that it corresponds more or less to the direction of the right oblique diameter, viz. that it runs from the right and backwards, obliquely forwards, and to the left. If we follow it with our finger in this last-mentioned direction, we come to a spot where it divides into or meets two other sutures; these are the right and left lambdoidal sutures, and beyond them is the hard convex occiput, the point where they meet being the posterior or occipital fontanelle. If we trace our finger along the suture in the other direction, viz. backwards and to the right, we shall come to a four cornered space, where four sutures meet at right angles to each other; these are the sagittal, the frontal, and right and left coronal sutures; the open space itself is the great or anterior fontanelle. That part of the head which lies lowest or deepest in the pelvis, and which the finger first touches upon when introduced along the vagina, is the right parietal protuberance; and if the os uteri be sufficiently dilated, we distinguish it by its hard and conical feel. In primiparæ, where the head usually is deep in the pelvis at the commencement of labour, and where the anterior and inferior segment of the uterus is closely stretched over it, the parietal protuberance may be felt through this part. Hence, then, the first position of the cranium, (or more correctly speaking, parietal bone,) is marked by the following characters: the sagittal suture crosses the os uteri, and runs parallel with the right oblique diameter of the pelvis: the vertex is therefore turned towards the upper part of the hollow of the sacrum, the posterior fontanelle forwards and to the left: the right perietal protuberance, therefore, is necessarily that part which is deepest in the pelvis; and the perpendicular diameter of the head, instead of corresponding to the axis of the pelvic brim, runs in an oblique direction upwards and forwards.