THE SKULL. 



FIG. 12. Infant's skull, showing anterolateral and postero- 

 lateral fontanelles. 



These fontanelles are of the greatest importance in diagnosing the position of 

 the head during labor. If the examining finger encounters first a large diamond- 

 shaped or four-cornered depression with its anterior angle more acute than the pos- 

 terior, the accoucheur will know that it is the anterior fontanelle which is presenting. 

 By following one of the sutures backward he will come to a triangular or Y-shaped 

 ridge which will be recognized from its shape as being the posterior fontanelle. He 

 will then know that the position of the 

 head is occipitoposterior. If the posi- 

 tion is the more usual occipito-anterior 

 one, the finger will first encounter the 

 posterior fontanelle with its three sutures, 

 which are distinctly recognizable. On 

 following the suture which leads back- 

 ward, the four-cornered anterior fon- 

 tanelle will be felt. The various sutures 

 constituting the fontanelles can usually 

 be distinctly felt, and, as the presenta- 

 tions are nearly always occipito-anterior, 

 the fontanelle that will usually be first 

 felt will be the posterior, and the sutures 

 forming it can readily be counted. 



The antero- and posterolateral fon- 

 tanelles, located at the anterior and pos- 

 terior angles of the parietal bones, are 

 of no service in diagnosing the position 

 of the head. They are indistinct, nearly 



closed, and thickly covered by tissue. In injuries to the skull in young children 

 and infants, we should not mistake the fontanelles and lines of the sutures for 

 fractures. Fissures extending into the occipital bone from the posterolateral fonta- 

 nelles are normal at birth and not due to injury. 



Dura Mater. The dura mater in children is more firmly attached to the 

 interior of the skull than in adults. If, therefore, a true fracture does occur, lacera- 

 tion of the dura is more 

 liable to be produced. This 

 firm attachment also pre- 

 vents the formation of epi- 

 dural hemorrhages, because 

 the force of the blow is not 

 sufficient to loosen the dura 

 from the bone, and when 

 the middle meningeal artery 

 is torn, as Marchant has 



pointed out, the bleeding 

 is more apt to be external 

 than internal. 



Cells and Air-sinuses. 

 The infant has the bones 

 of the face so slightly developed that there is no room for the cavities which after- 

 ward develop in them. The ridges of the bones also become more marked as age 

 advances. The young child has no superciliary ridges. 



The maxillary sinus, or antrum of High-more, and the mastoid antrum are the only 

 cavities that exist at birth. They are both much smaller than they ultimately become. 

 The mastoid antrum in relation to the size and age of the child is comparatively 

 large, being about five millimetres in diameter. As the bone in the child is unde- 

 veloped, and the tympanum lies nearer to the surface, the antrum likewise is some- 

 what higher and nearer to the surface than is the case in adults. This should be 

 borne in mind when operating on the bone in this region (Fig. 13). 



The frontal, elhmoidal, and sphenoidal sinuses appear about the seventh year, 

 but it is not until puberty is reached that they really begin to develop. The mastoid 



Mastoid antrum 



External 

 auditory meatus 



Mastoid process 



FIG. 13. The surface of the temporal bone has been chiselled off, 

 showing the relative size and position of the mastoid antrum and external 

 auditory meatus. 



