THE NASAL BONE. 81 



or spaces are left at the angles, which are called fontanelles, so named from the pulsations of 

 the brain, which are perceptible at the anterior fontanelle, were likened to the rising of water 

 in a fountain. The anterior fontanelle is the largest ; it is lozenge-shaped, and corresponds to 

 the junction of the sagittal and coronal sutures; the posterior fontanelle. of smaller size, is 

 triangular, and is situated at the junction of the sagittal and lambdoid sutures ; the remaining 

 ones are situated at the inferior angles of each parietal bone. The latter are closed soon after 

 birth ; the two at the two superior angles remain open longer ; the posterior being closed in a 

 few months after birth ; the anterior remaining open until the first or second year. These 

 spaces are gradually filled in by an extension of the ossifying process or by the development of 

 a Wormian bone. Sometimes the anterior fontanelle remains open beyond two years, and is 

 occasionally persistent throughout life. 



Supernumerary or Wormian 1 Bones. 



In addition to the constant centres of ossification of the skull, additional ones are occasion- 

 ally found in the course of the sutures. These form irregular, isolated bones, interposed between 

 the cranial bones, and have been termed Wormian bones or ossa triquetra. They are most 

 frequently found in the course of the lambdoid suture, but occasionally also occupy the situation 

 of the fontanelles, especially the posterior and, more rarely, the anterior. Frequently one is 

 found between the anterior inferior angle of the parietal bone and the greater wing of the 

 sphenoid, the pterion ossicle (Fig. 45). They have a great tendency to be symmetrical on the 

 two sides of the skull, and they vary much in size, being in some cases not larger than a pin's 

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

 form the whole 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, structure, 

 and mode of articulation they resemble the other cranial bones. 



Congenital Fissures and Gaps. 



An arrest in the ossifying process may give rise to deficiencies or gaps ; or to fissures, which 

 are of importance in a medico-legal point of view, as they are liable to be mistaken for fractures. 

 The fissures generally extend from the margins toward the centre of the bone, but the gaps 

 may be found in the middle as well as at the edges. In course of time they may become covered 

 with a thin lamina of bone. 



BONES OF THE FACE. 



The Facial Bones are fourteen in number viz. the 

 Two Nasal. Two Palate. 



Two Superior Maxillary. Two Inferior Turbinated. 



Two Lachrymal. Vomer. 



Two Malar. Inferior Maxillary. 



" Of these, the upper and lower jaws are the fundamental bones for mastication, 

 and the others are accessories ; for the chief function of the facial bones is to 

 provide an apparatus for mastication, while subsidiary functions are to provide for 

 the sense-organs (eye, nose, tongue) and a vestibule to the respiratory and vocal 

 organs. Hence the variations in the shape of the face in man and the lower 

 animals depend chiefly on the question of the character of their food and their mode 

 of obtaining it." 2 



The Nasal Bone. 



The Nasal (nasus, the nose) are two small oblong bones, varying in size and 

 form in different individuals ; they are placed side by side at the middle and upper 

 part of the face, forming, by their junction, "the bridge" of the nose (Fig. 46). 

 Each bone presents for examination two surfaces and four borders. The outer 

 surface is concave from above downward, convex from side to side; it is covered 

 by the Pyramidalis and Compressor nasi muscles, and gives attachment at its 

 upper part to a few fibres of the Occipito-frontalis muscle (Theile). It is marked 

 by numerous small arterial furrows, and perforated about its centre by a foramen, 

 sometimes double, for the transmission of a small vein. The inner surface is 

 concave from side to side, convex from above downward ; in which direction 



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

 these 1 >ones. 



2 W. W. Keen, American edition p. 185. 



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