The head of the infant at birth. Part I / by J.W. Ballantyne.

Date:
1890
Catalogue details

Licence: Public Domain Mark

Credit: The head of the infant at birth. Part I / by J.W. Ballantyne. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    each other. The cranium is clearly divided into two parts—the vault and tlie base. The vault is constituted by the two halves of the frontal bone, by the two parietal bones, and by that portion of the occipital bone which lies above the foramen magnum; at the sides also the squamous part of each temporal bone completes the framework of this part of the head. The base of the cranium is composed of the basi-occiput of the sphenoid, the ethmoid, and of the petrous part of the temporal bones. The bones whicli make up the vault differ from those tliat form the base, in being thinner and more loosely joined together; thus when pressure is brought to bear upon the vault the bones are displaced, and a change in the form of the head is the result; on the other hand, pressure does not affect to any appreciable degree the base of the cranium. In this anatomical fact is found the rationale of operations, such as basilysis, which not only diminish the size of the compressible vault, but also that of the incompressible base. The bones of the cranium are joined together by sutures; and those which lie within tlie sphere of touch during labour are the sagittal, the frontal, the coronal, and the lambdoidal. To the obstetrician the sagittal suture is a most important landmark. This suture connects together the upper margins of the two parietal bones, and derives its name from its resemblance to an arrow (sagitta); but it must be borne in mind that the resemblance to an arrow is manifest only when the anterior fontanelle is con- sidered as the head of the arrow. It is a matter of regret that all writers do not adopt the same definition of the sagittal suture. It is usually defined as terminating in front of the anterior fontanelle, and behind at the posterior fontanelle; but some authors include the fontanelles, and others, as Tarnier and Chantreuil (vol. i. p. 411), consider the frontal suture as forming the anterior portion of the sagittal, for they state that la suture sagittale, grande suture, ou suture antero-post^rieure, s'^tend de la racine du nez a Tangle superieur de I'occipital. It is better, however, to define this suture, as does the majority of writers, as that which exists between the upper margins of the parietal bones and which is bounded in front by the coronal and behind by the lambdoidal suture. At the commencement of labour, when the vertex pre- sents, the sagittal suture is found lying in one or other of the two diagonal diameters of the true pelvis, and the movement of internal rotation brings this suture into the antero-posterior diameter of the pelvis. The frontal, coronal, and lambdoidal sutures call for no special notice here. It is thus seen that in the head of the infant the bones of the vault are not immovably fixed to each other, as they are in the adult, but are loosely attached by a membrane composed of periosteum and dura mater, and can be moved to some extent upon one another. This constitutes one of the factors in head-moulding during labour. The presence of fontanelles, or openings in the head, is one