216 



AN 7 ATOMY. 



ces and cavities, having a considerably convex and 

 somewhat quadrangular shape. There is u genii-cir- 

 cular ridge, from which the temporal muscle ori- 

 ginates, and the foramen parietale, which is m-ar 

 the sagittal suture, and tr.m~a.u- an artery and u 

 vein to the dura mater. Upon its internal surface 

 are the grooves of the spinous artery, and when the 

 two bones are united, there is a deep cavity ex- 

 tending along the sagittal suture, for the longitud- 

 inal sinus of the dura mater. The connexion of 

 these bones with the os frontis, claims more par- 

 ticular notice than it often receives. In the mid- 

 dle of the coronal suture, where the frontal bone, 

 from its size and flatness, stands most in danger 

 of being injured, it rests upon the arch formed by 

 the parietal bones, whereas, at the sides, the par- 

 ietal bones rest upon the os frontis, because the 

 same arch is there in the greatest danger from 

 pressure. The surgical anatomy of the parietal 

 bones is very essential, especially a correct know- 

 ledge of the situation of the parietal foramen, for 

 when the artery which passes through it is divided, 

 it sometimes bleeds very profusely, and being em- 

 bedded, and somewhat retracted on the foramen, 

 cannot be secured by a ligature. These bones, at 

 birth, consist of one portion, and partake of the 

 shape of the adult bone, affording a very beautiful 

 exhibition of the radiated bony fibres, and the cen- 

 tre of ossification. 



One muscle only, viz., the temporal, is attached 

 to the parietal bone. 



The os occipitis, or occipital bone, (Plate III. fig. 

 2. No. 4.) is situated at the back of the head, forming 

 part of the base of the skull, and is somewhat of a 

 quadrate oblong shape. Its external surface is con- 

 vex, and very irregular, serving for the attachment of 

 various muscles. The inferior portion is stretched 

 forwards like a wedge, and at the base of this pro- 

 jecting portion are two condyles, or rounded emin- 

 ences, which serve for the articulation of the head 

 with the first vertebra of the neck. There are 

 numerous processes on its external surface, and 

 one upon the internal surface an internal cru- 

 cial spine, the superior branch of which gives adhe- 

 sion to the longitudinal sinus of the dura mater, 

 the two lateral to the lateral sinuses, and the in- 

 ferior to the septum ceribelli. 



There are likewise several cavities and depres- 

 sions, but the most remarkable circumstance con- 

 nected with this bone, which deserves special notice, 

 is the great opening or hole, technically the fora- 

 men magnum occipitale, through which the spinal 

 marrow proceeds into the spine and the vertebral 

 arteries and accessory spinal nerves into the cran- 

 ium. There are also two anterior condyloid fora- 

 mina, or openings for the passage of the lingual pair 

 ot nerves, two posterior foramina of the same kind 

 for the passage of the occipital vein into the lateral 

 sinus (which are'sometimes wanting.) There are 

 two notches, which with two corresponding notches 

 of the temporal bone, form another foramen in the 

 base of the cranium, for the passage of the blood 

 from the lateral sinuses into the jugular rein, and 

 the exit of the parvagum or eight pair of nerves ; 

 and a considerable groove leads to the above notches 

 in which the lateral sinuses are situated. The 

 internal surface has also four considerable depres- 

 sions, formed by the crucial spine we have noticed, 

 and the two superior contain the posterior lobes 

 of the. brain ; and the two inferior, the two lobes 

 of the cerebellum. 



" Mau being designed (as Dr Hooper pertinently 



remarks) for an erect posture, the foramen magnum 

 occipitale (or great ojiciiin;/ we have already alluded 

 to,) is placed nearly in the basis of the human cran- 

 ium, at almost an equal distance from the posterior 

 part of the occiput and the anterior part of the 

 lower jaw, whereas in quadrupeds it is nearer the 

 hack part of the occiput." This extraordinary hone 

 is connected with the sphenoid hone, the two par- 

 ietal and two temporal hones; and with the first 

 vertebrae of the neck by ginglymus, or a hinge-like 

 articulation : and to the second by syndesmosis, 

 or by means of ligaments. 



We have been more full and particular in our 

 description of this bone than perhaps our limits 

 justify, because we consider it to be one of the 

 most wonderful among the many contrivances of 

 the human body, in which the adaptation of means 

 to an end are so admirably displayed, that it 

 might form in itself subject sufficient for another 

 Bridgewater Treatise. It not only constitutes 

 the posterior and inferior part of the cranium, 

 but contains the posterior lobes of the brain, 

 the cerebellum and medulla oblongata, or upper 

 part of the spinal cord, and has been said (and 

 we think with some justice) to be the sensor- 

 ium commune, the organ of all the senses : but 

 yet, in addition to these important offices, the oc- 

 cipital bone also serves for the articulation of the 

 head with the spine, forming by far the most im- 

 portant joint of the human body. This subject 

 will, however, be further noticed in the section on 

 the spine and vertebrae. 



Again, if we except the petrous portion of the 

 temporal bone, the occipital will be found much 

 stronger than any bone of the head. The reasons 

 for this are sufficiently obvious, even to the most 

 thoughtless observer, as the occiput has to defend 

 the cerebellum, the least injury of which proves 

 fatal, and perhaps also because it is more liable to 

 be fractured, being, from its situation, less defended 

 than the other bones. For example, when we fall 

 forward, the hands naturally protect us ; and if on 

 one side, the shoulders greatly defend the head : 

 but when a person falls backwards, the hind part 

 of the head comes with considerable force against 

 the earth ; and if the fall is against a stone, or other 

 hard substance, the bone is either fractured or 

 knocked in, and presses upon the brain. In the 

 course of our practice, we have known several in- 

 stances of the kind. One in particular of a young man 

 about thirty, a type-founder in Edinburgh, whose 

 feet slipped from below him in coming out of a door, 

 on the steps of which was some ice : in falling, his 

 hat flew off and he fell heavily, his head striking 

 with great violence against the stone steps. He 

 died in about twelve hours after, and on opening the 

 head after death, the occipital bone was found to 

 have been beaten in. Its union with the parietal 

 and temporal bones, by the lambdoidal suture, was 

 loosened, and although not depressed more than 

 two lines of an inch, the surface of the brain was 

 covered with a cake of extravasated blood. 



This bone, at birth, is formed of four portions, 

 joined together by cartilages, an arrangement design- 

 ed to facilitate child-birth, or render child labour 

 less difficult and dangerous. The older anatomists 

 justly attached great importance to this bone, which 

 was by some denominated the os memories, or bone 

 that contained or defended the organ of memory ; 

 and by others, the os nervosum, because it lodged 

 or defended the chief, or most valuable part or 

 portion, of the nervous mass. It was also called 



