the lower and lateral part, and each is considered under three portions, viz., the pars squamosa, pars petrosa, and the mastoid portion, and its processes are considered under numerous subdivisions. (8) CHAP. IX. NERVOUS ORGANS. The Os Occipitis has also the names of os memoriæ (from its anciently being supposed to be the situation of the memory)(t) and os nervosum. This is situate immediately at the back part of the head. It is the thick- The occipital bone. est of the cranial bones; but it is the least regular in its thickness, being nearly transparent in some places, and in others swelling into ridges of very firm bone. It gives origin and insertion to many of the great muscles, which move the head and neck. It supports the back part of the brain, contains the cerebellum or lesser brain, transmits the spinal marrow, and is marked with the conflux of the chief sinuses or great veins of the brain.(u) bones. We have seen that there are two intermediate bones considered to be- The sphe long as well to the face as to the cranium, viz., the sphenoid bone and the noid and ethmoid bone. The sphenoid bone is situated towards the centre of the ethmoid base of the skull, and is articulated with all the bones of the cranium, and several of those of the face. Its form has been likened to that of a bat, and the resemblance is very close. Like other irregular bones it may be divided into a body, and processes or wings.(x) The ethmoid bone is common to the cranium, orbit and nasal fosse, and is of a cuboid figure; presents six surfaces, and is divided into two equal lateral parts by a perpendicular lamella; the superior part of which projects into the skull in the form of a cock's comb; the inferior descends into the nares, forming part of the septum. It has been considered as one of the most curious bones of the human body. It appears almost a cube, not of solid bone, but is exceedingly light, spongy, and consisting of many convoluted plates, which form a net-work like honeycomb. It is curiously enclosed in the os frontis, between the orbitary processes of that bone.(y) The bones of the cranium may be originally malformed, or may un- Of malfor dergo morbid changes, either by enlargement, deficient deposite of bone, mation or or imperfect ossification; or the bones may be insufficiently evolved, and defects, either deformed congenitally, or become thickened or enlarged by subse- and disquent circumstances; they may become ulcerated, carious, or dead, or bones of may have funguses or tumours, or be perforated, depressed or frac- the head in tured.(z) general. (s) 1 Bell, 64 to 72; 1 Horner, Anat. 135 to 138. (t) See ancient sketch, ante, 251. 134. 76. (x) 1 Horner, Anat. 138, 141; 1 Bell, (y) 1 Horner, Anat. 141 to 143; 1 Bell, 72. (z) See these disorders and injuries, Dict. tit. Cranium and Cretinism; Coop. and their remedies considered, Copl. Dict. tit. Head, and tit. Trephine; 2 Gibson, Surg. 122 to 130; Am. Cyclop. Prac. Med. tit. Acephalous and Anoncephalous. eases of Mem 1. Hairy Scalp. 4. Diploe. 3. (a) Inner Plate. 6. The Falx Cerebri, which 7. Cerebellum, or little Brain. 8. Medulla Oblongata. 9. The Lateral Ventricles. 10. The Arbor Vitæ of the Cerebellum. 11. Cavity of the Nose. 12. The Medulla spinalis. Besides the bony cranium, which we have thus considered, there is branes of an inner and threefold covering afforded to the brain, namely, the dura mater, the arachnoid (or tunica arachnoidea) and the pia mater,(a) termed the Membranes of the Brain. brain. Dura ma ter. The falx and tentorium. These membranes of the brain have the name of mater, either because they defend the brain and protect its tender substance; or, according to others, because they were supposed to be the source of all other membranes of the body. (b) The dura mater, so termed from its hardness, may be considered as the internal pericardium.(c) It lines the inside of the bones of the cranium, and may be considered their internal periosteum, and is a firm and somewhat opaque membrane of about the thickness of a finger nail. (d) When the skull cap has been torn off, and the dura mater has been cleared from the blood, which escapes from the ruptured vessels, it is seen marbled with azure and rosy colours. Its outer surface is rough, from the adhesion to the bone being torn up; but on the inner surface it is smooth, shining, and of a pearl colour.(e) The dura mater forms various processes or septa (Latin for fences.) which, by being extended across from the internal surface of the cranium, support the brain in sudden motions of the body, and prevent the mutual gravitation of its parts, and are also useful in retaining the sinuses or farge venous trunks in the brain, in their triangular form.(f) These large processes are termed the falx and tentorium. By the Falx the hemispheres of the cerebrum and cerebellum are divided perpendicularly from the top and centre of the cranium downwards towards its base, and from the front to the back, and appears to serve the like office as the mediastinum in the thorax, which we may remember passes perpendicularly through the thorax from the front to the back, and divides the right and left parts of the lungs; (g) whilst the Tentorium passes horizontally at the bottom of the cerebrum, and supports its posterior lobes, and prevents (a) El. Blum. 189; see the plate above. (b) See, in general, 2 Bell, 385; Coop. Dict. tit. Dura Mater, and tit. Head, Copl. Dict. 202, 203. (c) 2 Bell, 385; Coop. Dict. tit. Dura Mater; 2 Horner, Anat. 351. (d) 2 Bell, 485; Coop. Dict. tit. Dura Mater; 2 Horner, Anat. 352. (e) 2 Bell, 386; 2 Horner, Anat. 351. (f) Id. 390 to 392; 2 Horner, Anat. 352. (g) Ante, 99. SECT. II. NERVOUS FUNCTION AND ITS their pressure upon the subjacent cerebellum. In the various duplicatures CHAP. IX. of the falx and tentorium, they contain and support the venous sinuses, and prevent their too great local pressure on each other. The dura mater is considered as insensible of pain, and consequently is not so much the seat or organ of many diseases as has been supposed. (h) ORGANS. On each side of the dura mater, there are from ten to fifteen glands, chiefly lateral to the course of the longitudinal sinus, and from these issues a fluid. (i) The dura mater is supplied with numerous arteries, which sometimes become aneurismal and distended, sometimes, though rarely, causing epilepsy.(k) When the skull has been opened by a wound, it has been found that the dura mater will still protect the brain, resisting inflammation and giving it the necessary and uniform support. But when the dura mater is lacerated by the trephine or punctured, or worn by pulsation against the edge of the bone, there may be sudden hernia of part of the brain, from coughing, or a rapid and diseased growth from the pia mater forming a fungus.(1) Arachnoid (or, perhaps, more technically, tunica arachnoidea,) so named The arachfrom its thinness, it being like a spider's web, lying between the dura noid. mater and pia mater, and it is said that its use is not exactly known, but in some respects it resembles in office that of the pleura of the lungs, or the peritoneum of the abdomen. It is exceedingly delicate, perfectly transparent, and so intimately adherent to the dura mater, except at the base of the brain, as to admit with difficulty of separation from it. (m) It is described by some anatomists as destitute of blood vessels, and extended, like the dura mater, merely over the surface of the brain, without following the course of its furrows and prominences.(n) Some anatomists consider the arachnoid coat as the external lamella of the pia mater, and only a reduplication.(0) Indeed, it was formerly considered the same as the pia mater; but the contrary has been clearly established; and it has been observed that this membrane is in nature, office and disease, a close sac, affording, as the peritoneum does to the abdominal viscera, a double covering to the brain and spinal marrow and the nerves, before their departure through the foramina of the dura mater, and, according to Bichat, lining the ventricle, insulating the organs on which it lies, and affording them great facility of movement, and liable to the affections or diseases incident to other serous membranes.(p) The pia mater is closely attached to the brain, and passes into its inmost The pia recesses, following the course of its furrows and prominences. It is of the mater. thickness of thin paper, and while the dura mater is firm and opaque, and not prone to inflammation, the pia mater is delicate, transparent, extremely vascular, and peculiar in being easily inflamed. Like the dura mater, it is not itself endowed with sensibility, but it is of great strength considering its apparent delicacy.(q) It is composed of the finest cellular (h) El. Blum. 189; 2 Bell, 386, 387; but see Copl. Dict. tit. Cranium and tit. Brain; and Cyclop. tit. Headach. (i) 2 Bell, 387, 388; 2 Horner, Anat. 355. (k) Id. 389, 390; 2 Horner, Anat. 354. (1) Id. 395; 2 Gibson, Surg. 140. (m) See this noticed, Copl. Dict. tit. Brain; 2 Horner, Anat. 358, 359. (n) El. Blum. 189, 190; 2 Bell, 396; 2 Horner, Anat. 358; Lizars, 179; see dis- (o) 2 Bell, 295, note H; Copl. Dict. tit. (p) El. Blum. 199, note B. 2 Horn. Anat. 359. (q) 2 Bell, 395 to 399; 2 Horner, Anat. 360; see description of the pia mater and diseases, Copl. Dict. tit. Brain. CHAP. IX. tissue, for the purpose of conveying blood vessels to the surface of the SECT. II. brain in all its convolutions. NERVOUS AND ITS The diseases of the crani um. (r) Of the face. Thirdly, Organs of the ner vous sys tem.(v) The brain. Construction and As to the Diseases and Injuries to the head, independently of the brain and nerves, they are various, and will be considered in the next part.(r) The Face contains and encloses all the organs of sense, excepting those of touch and motion, viz. the organs of sight, hearing, smell, and taste, and part of the organs of mastication, deglutition, and of voice.(s) The great instruments of expressing the human passions and feelings are the muscles of the face, and when any passion is strongly marked and frequently repeated, these muscles acquire a tendency to continue in the same position, even when the corresponding feeling ceases to exist; and, by the frequent and powerful contraction of certain muscles, the shape of the neighbouring parts will be affected, and may be permanently extended or contracted, and even the bones of the face themselves may be somewhat altered in their form.(1) It is in respect of those consequences that physiognomists draw their conclusions respecting characters, but which we have seen ought not to be allowed any weight in judicial inquiries. (u) Having thus considered the organs and parts of the cranium and face which protect or support the sources of the nervous function, we are now to proceed to the parts of that function itself, namely, the brain, the spinal cord, the nerves, their plexuses and the ganglia, each of which must be examined separately.(w) The Brain is defined to be that soft mass contained within the cranium, from the lower part of which the cerebral nerves, which are essential to the organs of sense, and some of the nerves of sensation and motion, arise, spring, or are propagated.(x) It is considered as the centre to which the affections of the nervous system are to be referred.(y) With respect to the relation which the different parts bear to each other, it has been generally supposed that the brain is the centre of the nervous system, or that part to which all the others are subservient, and that the nerves receive impressions from external objects, and transmit such impressions to the brain, where they become sensible to the mind, constituting percep tions; (2) and it is universally agreed that the brain is the instrument of the intellectual powers, and as well the source of the sensific as of motionary power.(a) The Brain(b)is a body of a pulpy consistence, resembling a soft coagulum, filling the hollow bone called the skull, which gives the form to the head. composi- It is of an oval but extremely irregular figure, having a number of protion of the jections and depressions, corresponding partly to the irregularities of the skull (or more correctly, to which the skull, in its growth and ossification, brain. (w) 1 Bost. 176; 1 Dungl. Phy. 41. (x) 2 Bell, 365; Park's Inquiry, 8; 2 Horner, Anat. 350. (y) 1 Bost. 181. (2) 1 Bost. 196, 197; 4 Good, 1, 2. (a) 4 Good, 1, 2. (b) See in general, 2 Bell, 377; 1 Bost. 176; very fully in Copl. Dict. tit. Brain; Cyclop. Prac. Med. tit. Brain; tit. Insanity; Coop. Dict. tit. Head; 2 Horner, Anat. 350 to 401. FUNCTION AND ITS ORGANS. Ventricles has conformed,) (c) and partly produced by convolutions and cavities in the CHAP. IX. brain itself;(d) for its substance is composed of six lobes or divisions, two SECT. II. of which project anteriorly, two laterally, and two posteriorly. (e) We NERVOUS have examined its several coverings and membranes. It has internal cavities, which are called ventricles, and are lined with a serous membrane secreting an albuminous fluid, which, in the healthy state of the organ, is removed by absorption as rapidly as it is produced, but which is occasionally of the collected in considerable quantity, giving rise to the formidable disease of brain. hydrocephalus or water on the brain.(f) The brain is composed of two Cortical or substances differing in their situation, colour and consistence. The sub- cineritious, stance of the brain is of a peculiar nature, and cannot be easily described; and medulthe part towards the edges or outside is termed, from its situation, cortical, lary. or from its grayish colour cineritious (from cinis, wood ash,) whilst that part in and nearest the centre is white, of the colour and consistence of blancmange, and termed medullary. (f) The cortical part is sometimes described as of a reddish brown colour; it is of softer consistence than the medullary and has numerous blood vessels without fibrous appearance.(g) This more external portion of the brain may be pierced or cut, or even large masses of it may be removed, without any very material effect being produced upon the perceptive faculties; and Dr. Bostock observes, that frequently large abscesses are formed in it, or tumours and excrescences of various kinds, which, if they do not compress the remaining or medullary part of the brain, seem to produce little injury to its functions.(h) The medullary part is generally considered as constituting the nervous substance in its most perfect state, and Drs. Gall and Spurzheim have conjectured that the use of the cortical or cineritious part is to form or secrete the medullary part;(i) but even different parts of this medulla of the brain have been destroyed and yet the nervous powers have remained nearly in their ordinary state.(k) It is, moreover, established, that the medullary matter is in general more sensible than the cortical; and its sensibility increases as it approaches the centre of the brain, where is found a much more elaborate system of organization, and a much greater variety of separate parts, all of which we may fairly conclude serve some appropriate purpose connected with the nervous power.(?) The medullary part of the brain is composed of proper fibres with furrows between them; and which furrows or striæ are for the most part placed in such a direction as to converge towards the base of the brain, and it has been a question whether these fibres merely unite, forming what are termed commissures, or whether they actually cross each other and pass on the opposite sides of the body. Dr. Bostock, from observation, is of opinion that only a few of these fibres so cross each other.(m) It is, however, admitted, that it generally happens that an injury inflicted on one side of the brain exhibits its effect on the opposite side of the body, proving, at all events, the transmission of the nervous influence in that particular direction, whatever may be the physical structure of the organ.(n) Of late it has been discovered, that the brain is really composed of a pulp, containing a tant and interesting case of an insurance (i) 1 Bost. 178, note; 2 Bell, 377. (m) Id. 185, note; 4 Good, 3, |