80 OSTEOLOGY. 



the inferior angles of the parietal bone. The latter are closed soon after birth ; the two at the 

 superior angles remain open longer, the posterior one being closed in a few months after birth, 

 the anterior one remaining open until the first or second year. These spaces are gradually tilled 

 in by an extension of the ossifying process, or by the development of a Wormian bone. Fine 

 specimens of large Wormian bones closing in the anterior and posterior fontanelles, and replacing 

 the anterior inferior angle of the parietal bones, exist in the St. George's Hospital Museum. 

 Sometimes, the anterior fontanelle remains open beyond two years, and is occasionally persistent 

 throughout life. 



SUPERNUMERARY OR WORMIAN BONES. 



When ossification of any of the tabular bones of the skull proves abortive, the membranous 

 interval left unclosed is usually filled in by a supernumerary piece of bone, which is developed 

 from a separate centre, and gradually extends until it fills in the vacant space. These supernu- 

 merary pieces are called Wormian bones ;' they are called also, from their form, ossa triqwtm, 

 and present much variation in situation, number, and size. 



They occasionally occupy the situation of the fontanelles. Bertin, Cruveilhier, and Cuvier 

 liave each noticed the presence of one in the anterior fontanelle. There are two specimens in the 

 Museum of St. George's Hospital, which present Wormian bones in this situation. In one, the 

 skull of a child, the supernumerary piece is of considerable size, and of a quadrangular form. 



They are occasionally found in the posterior fontanelle, appearing to replace the superior angle 

 of the occipital bone. Not unfrequently, there is one replacing the extremity of the great wing 

 of the sphenoid, or the anterior inferior angle of the parietal bone, in the fontanelle there situated. 



They have been found in the different sutures on the vertex and side of the skull, and in some 

 of those at the base. They are most frequent in the lambdoid. Ward mentions an instance 'in 

 which one half of the lambdoid suture was formed by large AVormian bones disposed in a double 

 row, and jutting deeply into each other;' and refers to similar specimens described by Dumontier 

 and Bourgery. 



A deficiency in the ossification of the flat bones would appear in some cases to be symmetrical 

 on the two sides of the skull; for it is not uncommon to find these supernumerary bones corre- 

 sponding in form, size, and situation on each side. Thus, in several instances, I have seen a pair 

 of large Wormian bones symmetrically placed in the lambdoid suture ; in another specimen, a 

 pair in the coronal suture, with a supernumerary bone in the spheno-parietal suture of both sides. 



The size of these supernumerary pieces varies, in some cases not being larger than a pin's head, 

 and confined to the outer table ; in other cases so large, that one pair of these bones formed the 

 whole of that portion of the occipital bone above the superior curved lines, as described by 

 Beclard and Ward. Their number is generally limited to two or three ; but more than a hundred 

 have been found in the skull of an adult hydrocephalic skeleton. In their development, struc- 

 ture, and mode of articulation, they resemble the other cranial bones. 



CONGENITAL FISSURES AND GAPS. 



Mr. Humphry has called attention to the existence of congenital fissures, not unfrequently 

 found in the cranial bones, as the result of incomplete ossification. These fissures have been 

 noticed in the frontal and parietal bones, and the squamous portion of the temporal; they extend 

 from the margin towards the middle of the bone, and are of great interest in a medico-legal point 

 of view, as they are liable to be mistaken for fractures. An arrest of the ossifying process may 

 also give rise to the deficiencies or gaps occasionally found in the cranial bones. Such deficien- 

 cies are said to occur most frequently when ossification is imperfect, and to be situated near the 

 natural apertures for vessels. Mr. Humphry describes such deficiencies to exist in a calvarium, 

 in the Cambridge Museum, where a gap sufficiently large to admit the end of the finger is seen 

 on either side of the sagittal suture, in the place of the parietal foramen. There is a specimen 

 precisely similar to this in the Museum of St. George's Hospital ; and another, in which a small 

 circular gap exists in the parietal bone of a yonng child, just above the parietal eminence. 

 Similar deficiencies are not unfrequently met with in hydrocephalic skulls ; being most frequent, 

 according to Mr. Humphry, in the frontal bones, and in the parietal bones, on either side of the 

 sagittal suture. 



BONES OF THE FACE. 



The Facial Bones are fourteen in number, viz., 



Two Nasal, Two Palate, 



Two Superior Maxillary, Two Inferior Turbinated, 



Two Lachrymal, Vomer, 



Two Malar, Inferior Maxillary. 



1 Wormius, a physician in Copenhagen, is said to have given the first detailed description of 

 these bones. 



