=The head= is the most important part of the fetus, from an obstetrical standpoint, since the process of labor is virtually a series of adaptations of the size, shape and position of the fetal skull to the size and shape of the maternal pelvis. And since the pelvis is rigid and inflexible the adjustment must all be made by the fetal head, which is mouldable because of being incompletely ossified at birth. If the head passes through the inlet safely, the rest of the delivery will usually be accomplished with comparative safety. But a marked disproportion between the diameters of the head and pelvis, or limited mouldability of the head, constitutes a serious complication, which will be discussed later in connection with obstetrical operations. A baby’s head is larger, in proportion to its body, than an adult’s, while the face forms a relatively smaller part of the baby’s than of the adult’s head. The major portion is the dome or vault-like structure forming the top, sides and back of the head, which in turn is made up of separate and as yet ununited bones. They are the two _frontal_, two _parietal_, two _temporal_ and the _occipital_ bone, with which the wings of the _sphenoid_ bones, though less important, may be included. These bones are not joined in the fetal skull, but are separate structures, with soft, membranous spaces between their margins, called _sutures_; while the irregular spaces formed by the intersection of two or more sutures are called _fontanelles_, possibly so called by the early observers because the pulsation of the soft tissues beneath these spaces suggests the spurting of a fountain. The sutures are named and situated as follows: The _frontal_ lies between the two frontal bones; the _sagittal_ extends antero-posteriorly between the parietal bones; the _coronal_ between the frontal bones and the anterior margins of the parietal, while the _lambdoidal_ suture separates the posterior margin of the parietal from the upper margin of the occipital bone. There are also the temporal sutures between the upper margins of the temporal bones and the lower margins of the two parietals, but they are of no obstetrical importance, as they cannot be felt on vaginal examination. (Fig. 30.) There are two fontanelles of obstetrical significance. The greater, or _anterior fontanelle_, also called the _bregma_ or _sinciput_, is located at the meeting of the coronal, sagittal and frontal sutures. It is diamond or lozenge shaped, about an inch in diameter and is not obliterated during labor. [Illustration: FIG. 30.—Side and top views of fetal skull giving average length of important diameters. ] The smaller or _posterior fontanelle_ is the triangular space at the inter-section of the sagittal and lambdoidal sutures, and may be obliterated as the surrounding bony margins approach each other during labor.