(From the Hebrew term kabah, an helmet). The head. The parts in the lower cavities are the seat of the vital, and in the upper, of the animal powers; the latter is the seat from whence all sensation is derived. See Cerebellum and Cerebrum.
Besides the external integuments of the head, then-is an aponeurotic expansion which covers it like a cap. It is also spread round the neck and on the shoulders like a riding hood; for which reason Wins-low calls it coif, and the superior portion of it the aponeurotic cap. It is very strong, and appears to be made of two strata of fibres crossing each other; as it spreads to the neck it becomes thinner, and is lost insensibly on the clavicles. It sends out a production on each side from above downward, and from without inward, which having passed over the superior extremity of the musculus mastoideus, runs behind that muscle toward the transverse apophysis of the vertebrae of the neck, where it communicates with the intertransversalia ligamenta. See Pericranium.
The head comprehends the cranium and the face; the cranium is distinguished into the upper and lower parts. The base of the skull externally is very uneven; internally it is divided into three pair of cavities, and one azygous cavity. The first pair are above the orbit, in which the anterior lobes of the cerebrum are placed; and the next pair contains the middle lobes; the posterior pair arc placed behind the foramen magnum oc-cipitalc, where the posterior lobes of the cerebellum are lodged. The azygous cavity is situated upon that part of the sphenoid bone called the ephippium, or sella turcica, where the glandula pituitaria lies.
The bones of the upper part of the cranium are nearly of the same thickness. Where the bone is thick there is a larger space occupied by the meditullium, which consists of cancelli, formed by the interlacing fibres, as in the heads of the long bones; where they arc very thin there is no meditullium, whence in the latter case the cranium is transparent, in the former opaque. The cranium is laterally depressed, which serves to enlarge the sphere of vision, and to increase the strength of the skull on its fore and hind parts, by making them more convex; which is a necessary contrivance to prevent injuries from falls, for we seldom fall on the sides. See Facies and Cranium.
The best way of forming a perfect idea of the bones of the head is to have a skull, the bones of which are separated by art; and another, in which they are connected in their proper articulations.
The nerves from the fifth pair, and the portia dura, so called from its former consistence, of the seventh, are distributed through the external parts of the head.
Through the small foramina of the os ethmoides the
C A P 6 A It filaments of the first pair of nerves pass to the nose, and are called olfactory nerves.
In the os sphenoides, immediately behind, is the foramen opticum, through which the second pair of nerves, railed the optic, pass. This hole, which is seated below the anterior clinoid process, likewise admits the branch of the carotid artery that goes to the eye.
The foramen lacerum superius on each side lies between the transverse spinous, and orbital- processes of the os sphenoides: through this hole the three pair of nerves, called motores oculi; the fourth pair or pathetic; the first branch of the fifth pair; the whole sixth pair, except one reflected branch; and an artery from the internal carotids, pass to the orbit.
Behind the last mentioned hole, in the same bone, is the foramen rotundum, through which the second branch of the fifth pair of nerves, called the superior maxillary nerves, pass to the bottom of the orbit.
Between the pars petrosa of the os temporis, and the process of the os sphenoides, is an oblong aperture, through which the carotid artery passes, running inwards and upwards to the sella turcica, and thence to the clinoid processes, where it passes through the dura mater.
The portio mollis of the seventh pair of nerves, called the auditory nerve, is distributed to the meatus audito-rius internus; the portia dura comes out by the aqueduct. The eighth pair of nerves, called the par Vagum, pass out by that common hole, between the temporal and occipital bones; where likewise the internal jugular vein, which is a continuation of the transverse sinus, goes out of the cranium.
The ninth pair of nerves pass through the holes of the occiput above the condyles.
The tenth pair of nerves pass through the foramen magnum, where likewise the vertebral arteries enter.
The external eminences are, the two mastoid processes, the two styloid processes, the two condyloid processes, the two pterygoid, the two arches called zygomata, the external spine of the occiput, the condyloid and coronoid apophyses of the lower jaw.
The principal uses of the bones of the head arc, to contain the brain, to be the seat of the organs of sensation, to serve for mastication, respiration, and the formation of the voice. There is sometimes a disorder of the head, which draws it to one side, called contorsio.
Eustachius' tables of the bones of the head are good. See Window's Anatomy, and Monro's Osteology.
Capit. See Capita, and Processus.
Caput concutiens. See Intertransversales Boili.
Caput gallinaceum. See Onobrychis.
Capit mortuum. A dead head. In chemistry-it imports the dry faeces left in a vessel after the moisture hath been distilled from it. It is also called terra damnata, and mortua terra. The earthy part of moist bodies serves as a basis to the other principles; it is that which unites and gives them solidity. When the active principles are extracted, it is consequently called caput mortuum.
Caput obstipicm. See Cervix.