Occipital lobe

“ The corpora geniculata, thalami, and subcortical fibres leading to the occipital lobes are also found atrophied in these cases. The phenomena are not uniform, but are indisputable; [30] so that, taking all lines of evidence together, the special connection of vision with the occipital lobes is perfectly made out. It should be added that the occipital lobes have frequently been found shrunken in cases of inveterate blindness in man.
Hearing.
Hearing is hardly as definitely localized as sight. ”

“ In old animals the interparietal forms the hind part of a prominent ridge running along the mid-dorsal surface of the skull and called the sagittal crest, while the junction line of the occipital and parietal segments forms a prominent occipital crest.
The plane in which the bones of the occipital segment lie is called the occipital plane; the angle that it makes with the basicranial axis varies much in different mammals. ”

“ To an anatomical eye the posterior part of the skull is even more striking than the anterior. The occipital protuberance occupies the extreme posterior end of the skull when the glabello-occipital line is made horizontal, and so far from any part of the occipital region extending beyond it, this region of the skull slopes obliquely upward and forward, so that the lambdoidal suture is situated well upon the upper surface of the cranium. ”

“ The supra-occipital bone is visible from behind; its top is covered and partly fused with a continuation of the parietals, which are, like the frontals, fused into an unpaired mass. The occipital condyle is formed entirely by the basi-occipital bone, so far as the articulating facet is concerned, but it is supported on either side by a lamella from the lateral occipitals. ”

“ In man the strong forward inclination of the nuchal portion of the occipital bone is considered to have a relation to the upright position. I can not see why it should not be interpreted in the same way in the fossil skull under consideration. ”

“ The semicircular line indicating the upper boundary of the attachment of the temporal muscle, though not very strongly marked, ascends nevertheless to more than half the height of the parietal bone. On the right superciliary ridge is observable an oblique furrow or depression, indicative of an injury received during life. 7
mm. 8 The length of the skull from the nasal process of the frontal over the vertex to the superior semicircular lines of the occipital measures.............................303 (300) = 12.0". ”

“ The parietals and frontals, being membrane bones, are not comparable to the supra-occipital, in the way that the presphenoid and basisphenoid are to the basi-occipital. [20]
The cartilage bones of the occipital segments are derived from the parachordals of the embryonic skull, those of the parietal and frontal segments from the trabeculae. ”

“ Every one who is acquainted with the pliable condition of the cranial bones at birth, will readily conceive how effectually this apparatus would mould the head in the elongated or cylindrical form; for, while it prevents the forehead from rising, and the sides of the head from expanding, it allows the occipital region an entire freedom of growth ”

“ The massive intermaxillary bone had its posterior margin of an angular form, and into the notch thus formed there was wedged the anterior end of a long strip of plates, which expanded as they approached the occipital part of the cranium, and terminated in three irregular plates that may represent the place of the parietal and occipital bones. ”

“ The new doctrine he expounded was received in Germany with great enthusiasm by the school of the philosophers of nature. The author conceived the cranium to consist of three vertebræ, and the basal occipital, the sphenoid, and the ethmoid, were regarded as the central parts of these cranial vertebræ. On these alleged bodies of vertebræ, the arches enveloping the central parts of the nervous system were raised, while on the opposite side were attached the inferior pieces, which went to form the vegetative arch destined to embrace the intestinal canal and the large vessels. ”

“ They are interrupted in front by the strong palpebral ridges which extend backward from a point opposite the anterior pair of glabellar furrows and merge into the arched palpebral lobes; in front of the palpebral ridge the cheeks descend rapidly and merge into the frontal limb; the postero-lateral limb is long and almost entirely made up of the rounded, narrow posterior rim, strong intermarginal furrow, and a narrow area between the furrow and the facial suture. Palpebral lobe of medium length; in a cephalon 18 mm. ”

“ The occipital and frontal muscles, united by a thin aponeurosis, cover the whole upper cranium and are known as the occipito-frontalis muscle. At the back this is attached to the occipital bone, while in front it interlaces with various face muscles. It is a powerful muscle and raises the brows, wrinkles the forehead, and draws the scalp forward. Long hair grows on the skin over it as a further protection against blows upon the skull and sudden variations in temperature. ”

“ Recognizing in the scapular bones the ribs of the occipital centrum, the anatomists of this school of course consider them, when found articulated to the occiput, as in their proper and original place, and as in a state of natural dislocation when removed, as in all the reptiles, birds, and mammals, farther down. We find Professor Oken borrowing support to his hypothesis from this view. The limbs, he tells us, are simply ribs, that in the course of ages have been set free, and have become by development what they now are. ”

“ A low arching ridge separates the glabellar and neck depressions.
The occipital depressions include the spaces within the "doublure," glabellar ridges, and neck depression. Occipital cavity in the anterior lateral third. Glabellar and occipital depressions finely punctate.
The neck depression extends laterally as shallow grooves under the "doublure," deepest towards the central depression. Central depression a concave groove, the posterior margin reflected upward and forward, terminating in a thin edge, which articulates with the articular fold of the first thoracic segment. ”

“ The occipital nerve penetrates the lateral wall of the cranium close behind the root of the vagus and enters the canal of the vagus, along which it passes. On emerging, it sends small branches to the nearby muscle, while the principal portion runs on to join the hypobranchial nerve. The occipital nerve will be found to arise from the ventral surface of the medulla, below and behind the root of the vagus, by two or more distinctly separated roots, which may represent distinct nerves. ”

“ The skull consists of a cartilaginous cranium, and of jaw and visceral arches. The cranium persists throughout life, in what closely resembles a transitory embryonic condition of the higher types. There is a nasal capsule (na.c.) , a brain case proper, and lateral otic (auditory) capsules (ot.c.) containing the internal ear. (This should be compared with the frog's embryonic skull.) The upper jaw has a great bar of cartilage, the palato-pterygoid, as its sole support; the arch of premaxilla, maxilla, jugal, and squamosal-- all membrane bones-- is, of course, not represented. ”

“ The skull forms a bony envelope for the brain, just as the vertebral canal does for the spinal cord; and as the brain is only a peculiarly differentiated part of the head, while the spinal cord represents the longer trunk-section of the originally homogeneous medullary tube, we shall expect to find that the osseous coat of the one is a special modification of the osseous envelope of the other. When we examine the adult human skull in itself (Figure 2.332) , it is difficult to conceive how it can be merely the modified fore part of the vertebral column. ”

“ The left posterior occipital position.—Delivery is effected the same in this as in the left anterior, or first position, excepting that the rotation is more extended, owing to the occiput being behind, as explained in the right posterior occipital position. ”

“ The several constituents of the lower jaw are not to be distinguished in the adult mammal.
(3) The frog has no lachrymal bone. Section 36. We are now in a position to notice, without any danger of misconception, what is called the segmental theory of the skull. Older anatomists, working from adult structure only, conceived the idea that the brain-case of the mammal represented three inflated vertebrae. The most anterior had the pre-sphenoid for its body, the orbito-sphenoids for its neural processes, and the arch was completed above by the frontals (frontal segment) . ”