CRANIUM. 



737 



tal to the two parietal bones (fig. 373, a). 

 The lambdoidal (o) consists of two diverging 

 lines formed by the articulation of the posterior 

 border of the two parietals with the superior 

 half of the occipital ; and extends from the 

 superior to the lateral angles of that bone. 

 The sagittal is the line of union between the 

 parietals themselves, and runs longitudinally 

 from the superior part of the lambdoidal to 

 the centre of the coronal suture. On each side 

 of the skull is the squamous suture (Jig- 373, 

 e) ; it has none of the serrated characters of 

 the other sutures, but is an arched line ex- 

 tending from the great wing of the sphenoid 

 to the mastoid process of the temporal bone, 

 and traversing so much of the border of its 

 squamous process as embraces the parietal 

 bone. 



The squamous suture and the lambdoidal 

 suture are connected by a short transverse line 

 formed by the articulation of the mastoid angle 

 of the parietal bone with the mastoid process 

 of the temporal, and which is called addita- 

 mcntum sutura squamosa (fig- 373, g). From 

 the lateral angle of the occipital bone to its 

 jugular process, that is, from the termination 

 of the lambdoidal suture (where it is joined by 

 the before-mentioned supplement of the squa- 

 mous suture) to the jugular foramen, there is 

 a line formed by the posterior border of the 

 mastoid process and the occipital bone termed 

 additamentum suturtB lambdoidalis. 



The transverse frontal suture (Jig. 373, a) 

 is situated transversely, but forms several 

 angles in its course. It extends from one 

 external angular process of the frontal bone to 

 the other; commencing at either angle, after 

 uniting that angle to the malar bone, it enters 

 the orbit, and unites the frontal bone to the 

 great wing and to the small wing of the sphe- 

 noid ; it then passes out of the other side of 

 the orbit, joining the same bone to the eth- 

 moid, lachrymal, nasal process of the superior 

 maxillary and nasal bones themselves ; enters 

 the orbit of the opposite side and retires from 

 it, articulating the frontal to bones analogous 

 to those in the other orbit. 



Other sutures are occasionally enumerated, 

 such as the sphenoidal, which entirely sur- 

 rounds the sphenoid bone ; and the ethmoidal, 

 which bounds the cribriform plate of the eth- 

 moid bone. Both of these, so far as they 

 deserve the name of sutures, are comprehended 

 in the transverse frontal suture. 



The articulations of the temporal with the 

 occipital, sphenoid, and parietal bones have 

 been designated as the petro-occipilal, petro- 

 sphenoidal, spheno-temporal, and spheno-pari- 

 etal sutures; but, with the exception of the 

 last, (which is squamous, and truly a part of 

 that suture,) they are not sutures. 



It ought further to be remarked that, while 

 the bones of the calvaria are much thinner 

 than those of the base, they are comparatively 

 thicker in their borders to allow of that serra- 

 tion from which the term suture is derived. 



To study, in combination with each other, 

 the facts enumerated in the foregoing descrip- 

 tion, it is necessary to take a survey of the 



external and internal surfaces of the skull 

 itself. 



For this purpose the external surface may 

 be divided into four regions : the superior, the 

 inferior, and the two lateral. 



The superior region extends from the nasal 

 process of the frontal bone to the occipital 

 protuberance, and is bounded on each side 

 by the linea temporalis; a curved line, which, 

 commencing at the external angular process 

 of the frontal bone, passes backwards, traverses 

 the parietal below its protuberance, and is re- 

 ceived on the extreme point of the root of the 

 zygomatic process of the temporal bone. To 

 proceed from before to behind, there are, on 

 the median line, the nasal process and the 

 rough notch for the articulation of the nasal 

 bones; the nasal protuberance; the glabella 

 bounded laterally by the frontal processes; the 

 line indicating the junction of the two foetal 

 portions of the frontal bone ; the centre of the 

 coronal suture; the whole length of the sa- 

 gittal suture, with the foramen parietale on 

 each side of it; the superior angle of the 

 occipital bone ; a part of the occipital bone 

 itself; and, lastly, the occipital protuberance. 

 Laterally, and on each side, there are the 

 frontal process, the superciliary ridge, the 

 depression between them, and the supra-or- 

 bitary foramen ; the frontal protuberance ; the 

 coronal suture ; the parietal protuberance ; the 

 lambdoidal suture ; and so much of the side 

 of the occipital bone as is above the transverse 

 ridge. 



The inferior region extends from the pos- 

 terior part of the nasal process to the occipital 

 protuberance, and is circumscribed by a line, 

 continuous with the extremities of the supe- 

 rior curved ridge of the occipital bone, and 

 passing on the outside of the mastoid and in 

 the direction of the zygomatic process of the 

 temporal bone, to the crest which is on the 

 temporal process of the great wing of the sphe- 

 noid. The facts to be here noticed are nu- 

 merous, and, to facilitate their enumeration, 

 this region may be divided into three parts, 

 one anterior to the pterygoid processes of the 

 sphenoid bone, one posterior to the articu- 

 lating processes of the occipital bone, and a 

 middle one between these two. 



The anterior division contributes to form the 

 nose and the orbits. For the first, there may 

 be observed on the median line, the nasal 

 lamella of the ethmoid bone, articulated, in 

 front, to the nasal process of the frontal, and, 

 behind, to the crest in front of the body of the 

 sphenoid. On the same line, but below and 

 behind this, is the azygos process, and inferior 

 part of the body of the sphenoid, with the 

 channels to form, with the vomer, the palatine 

 canals. On either side of the nasal lamella is 

 the slit for the ethmoidal nerve and vessels ; 

 the cribriform plate and its foramina ; and the 

 space which assists to form the nares. More 

 laterally, and still passing from before back- 

 wards, is the internal angular process of the 

 frontal bone, to unite with the lachrymal ; the 

 cellular mass of the ethmoid, with its turbi- 

 nated processes on one of its sides, and the 



