14 ANTHROPOLOGY. 



central line on the outer surface shows the line of union of the two sjin- 

 metrical halves into which the bone is divided when young (pi. 121, ßg. 

 7 ') ; this line is often replaced, especially in the young, by a suture called 

 the frontal suture. The frontal protuberances (ßg. 7^) over the eyes 

 mark the centres of ossification in the foetus : the superciliary ridges {ßg. 

 7') below these serve for the attachment of the muscle for wrinkling 

 the eyebrows. Nearly in the middle of the upper-orbitar border is a 

 foramen or notch {ßg. 4^, 7°), the supra-orbitary foramen for the passage 

 of the supra-orbital artery, veins, and nerve. The inner face of the bone 

 is strongly marked by depressions corresponding with the convolutions of 

 the brain, and also caused by impressions of bloodvessels {ßg. 8 '• ^' ^). On 

 its middle exists a vertical ridge becoming more elevated as it approaches 

 the ethmoid bone, and terminating below in the foramen coecum {ßg. 5'), 

 occupied by a process from the great falx of the dura mater as well as by 

 some very small veins. At the exterior angular part of the orbitar process 

 of the frontal bone is a depression for receiving the lachrymal gland and 

 called the lachrymal fossa {pi. 123, ßg. 1 ') ; on the nasal side there is a 

 smaller depression or a small spine, fossa or spina trochlearis {ßg. 1 *\ 

 serving as a pulley for the superior oblique muscle of the eye. Separating 

 the two orbitar processes, is a large notch for receiving the cribriform plate 

 of the ethmoid bone {ßg 1 '), and on each side of this are cells {ßg. 1 '), 

 which are continuous with those of the ethmoid. 



The parietal bones, ossa parietalia {pi. 121, ßg. 1^, ßg. 4', ßg. 5*, ßg. 9, 

 interior surface). These bones are quadrilateral, convex externally, con- 

 cave internally. They constitute the superior and lateral portions of the 

 middle of the cranium, abutting against each other» along its median line. 

 Externally they are smooth, but raised about their middle into the parietal 

 protubei'ances, the centres of ossification ; below these protuberances there 

 is an arched, broad, but slightly elevated ridge for the attachment of the 

 temporal fascia and muscle, and continuous with the ridge on the side of 

 the frontal bone. The internal surface is marked by the convolutions of 

 the brain, and also exhibits a number of arborescent furrows produced by 

 the ramifications of the middle artery of the dura mater {pi. 121, ßg. 9 '). 

 At the inferior posterior corner of the bone there is also a fossa, which is 

 made by the lateral sinus of the dura mater {ßg. 9^). 



The occipital bone, os occipitis {pi. 121, ßg. 1% ßg. 6', ßg. 17, external 

 surface ; ßg. 18, internal). It forms part of the posterior and inferior walls 

 of the cranium, and when anchylosed with the sphenoid, as is usually the 

 case in advanced age, constitutes the basilar bone, os basilare. On the 

 posterior external surface, and half-way between the foramen magnum and 

 the upper angle of the bone, is seen the occipital protuberance, from the 

 lower part of which a small vertical ridge is extended towards that fora- 

 men. Into this ridge is inserted the ligamentum nuchae. From either 

 side of the protuberance an arched ridge extends to the lateral angle of the 

 bone, known as the superior semi-circular ridge or line; in addition to 

 these we see another ridge and various cavities {ßg. 17'' '' '' ") for the 

 attachment of muscles. In the lower section of the bone is the foramen 

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