Spinet

“ Manifestly, at the end of the spine, Nature puts out smaller spines, as arms; at the end of the arms, new spines, as hands; at the other end, she repeats the process, as legs and feet. At the top of the column she puts out another spine, which doubles or loops itself over, as a span-worm, into a ball, and forms the skull, with extremities again: the hands being now the upper jaw, the feet the lower jaw, the fingers and toes being represented this time by upper and lower teeth. This new spine is destined to high uses. It is a new man on the shoulders of the last. ”

“ The flexibility and strength of the spine, the exquisite fitting of its joints, the small head capable of being turned in almost any direction in the search for prey or the avoidance of danger, the wonderful arrangement of levers afforded by the limbs, which exhibit at once the greatest amount of strength and the greatest amount of elasticity, all combine to fill the mind with wonder and admiration, as great as that excited by the most perfect work of art or the most stupendous phenomenon of inanimate nature. ”

“ The habitual rigidity of the spine, as compared with its possible freedom, is more noticeable in training, of course, than is that of any other part of the body. Each vertebra should be so distinctly independent of every other, as to make the spine as smoothly jointed as the toy snakes, which, when we hold the tip of the tail in our fingers, curve in all directions. Most of us have spinal columns that more or less resemble ramrods. It is a surprise and delight to find what can be accomplished, when the muscles of the spine and back are free and under control. ”

“ The spinal nerves are those nerves which arise from the sides of the spinal cord. They differ from the cranial nerves not only in their origin outside the cranium, but also in that each spinal nerve arises by two roots which spring from the spinal cord near the dorsal and ventral surfaces. Each root passes through a foramen in the cartilaginous wall of the neural canal, the ventral a little anterior to the dorsal, after which they unite to form the spinal nerve. ”

“ Spin′āte, covered with spines or spine-like processes.—Spinal column, the backbone; Spinal cord, marrow, the main neural axis of every vertebrate.
Spindle, spin′dl, n. the pin from which the thread is twisted: a pin on which anything turns: the fusee of a watch: anything very slender.—v.i. to grow long and slender.—adjs. Spin′dle-legged, -shanked, having long slender legs, like spindles.—ns.pl. Spin′dle-legs, -shanks, long slim legs—hence an over-long and slender person.—adj. Spin′dle-shaped, shaped like a spindle: thickest in the middle and tapering to both ends.—ns. ”

“ The use of this chair is more efficacious in straightening the spine, than simply lying down horizontally; as it not only takes off the pressure of the head and shoulders from the spine, but at the same time the inferior parts of the body contribute to draw the spine straight by their weight ”

“ In Man, in consequence partly of the disposition of the articular surfaces of the vertebrae, and largely of the elastic tension of some of the fibrous bands, or ligaments, which connect these vertebrae together, the spinal column, as a whole, has an elegant S-like curvature, being convex forwards in the neck, concave in the back, convex in the loins, or lumbar region, and concave again in the sacral region; an arrangement which gives much elasticity to the whole backbone, and diminishes the jar communicated to the spine, and through it to the head, by locomotion in the erect position. ”

“ In addition to these peculiarities, we may remark, that the spine makes a sudden twist near the head to one side; that the bones of the head are not symmetrical; that the two sides of the mouth are unequal; that the pectoral and ventral fins of the under side are generally smaller than those of the upper; and that the dorsal and anal fins generally correspond to each other, the one fringing the whole length of the dorsal, the other that of the ventral edge of the body. ”

“ The pedicles extend back from the body on either side and support two broad plates of bone, the laminæ, whose juncture at the back completes the spinal foramen for the passage of the cord. At their juncture is the spinous process, which can be felt beneath the skin, while the transverse processes project from the juncture of the laminæ with the pedicles. All the processes are for the attachment of muscles that move the spine. The body is formed of cancellous bone with a compact layer outside. ”

“ A. I thank you, Isabel. Now, what is this spine, of which there is so much "complaint" now-a-days?
I. I will answer you from Paley: "The spine, or backbone, is a chain of joints of very wonderful construction. It was to be firm, yet flexible; firm, to support the erect position of the body; flexible, to allow of the bending of the the trunk in all degrees of curvature. It was further, also, to become a pipe or conduit for the safe conveyance from the brain of the most important fluid of the animal frame, that, namely, upon which all voluntary motion depends, the spinal marrow ”

“ When the spine is erect, they are of the same thickness all around. When the spine is bent sidewise, say towards the right, the elastic cushions become thinner on that side, and if the bending is decided, the edges of the spinal bones themselves will nearly touch, while the mass of elastic or india-rubber substance will be pressed over to the left side. Now suppose that one follows an occupation requiring this position of the spine. ”

“ Bony prominences.—The anterior superior spine of the ilium, the spine of the pubes, and the line of Poupart’s ligament, are landmarks with which every surgeon should be thoroughly familiar.
68. Spine of ilium.—The spine of the ilium is the spot from which we measure the length of the lower extremity. It is a valuable landmark in determining the nature of injuries to the pelvis and the hip. The thumb easily feels the spine, even in fat persons. Its position with regard to the trochanter major should be carefully examined. ”

“ The spine system is grouped and spreading, with four to seven central spines sometimes three inches in length, often crooked or twisted, and surrounded by smaller radials scattered along the stem ridges, not more than a fourth-inch to an inch long, all thorns of a beautiful golden or light translucent yellow. The spines often vary in their general characteristics, long and short, twisted and bulbous, straight and bent and twisted, flat and grooved, tough and easily broken. ”

“ The spine is composed of vertebrae, and it extends from the head down to the loins. The vertebrae are all perforated, and, above, the bony portion of the head is connected with the topmost vertebrae, and is designated the 'skull'. ”

“ When the spinal cord has been severed in the neck this scratching movement of the hind limb can be elicited with regularity as a spinal reflex by merely rubbing the skin of the side of the neck or shoulder, applying there a weak electric current to the skin. In this reflex the stimulus excites afferent nerves connected with the hairs in the skin and these convey impulses to the spinal centres in the neck or shoulder segments, and these in turn discharge impulses into nerve fibres entirely intraspinal passing backward along the cord to reach motor centres in the hind limb region. ”

“ All along the spinal column, and between each two adjoining bones, are openings on each side, through which nerves pass out to be distributed to various parts of the body.
Between the vertebræ are pads or cushions of cartilage. These act as “buffers,” and serve to give the spine strength and elasticity and to prevent friction of one bone on another. Each vertebra consists of a body, the solid central portion, and a number of projections called processes. ”

“ At each antero-lateral angle a strong, backward-curving spine (a') complements the great dorsal thoracic spines. A pair of large crescentiform sessile eyes occur on the anterior margin just within the base of the anterior spines (pl. 25, figs. 4 and 5) . The great dorsal spines are beautifully crenulated on the outer margin by short, strong backward-curving spines.
Appendages.—The antennæ (a", fig. 5, pl. 26) are long, slender, and many-jointed; they unite with the head near the posterior end of the labrum ”

“ The spinal cord, as we have seen, is a mass of nervous substance continuous with the brain; from the spinal cord nearly all the nerves of the body are given off; those nerves whose branches go to the biceps muscle in the arm leave the spinal cord somewhere in the neck. ”

“ There are also proper webs lined with fur for the hands to take hold off occasionally, and also to go under the arms. By these means I should hope great advantage from gradually extending the spine during the inactivity of the muscles of the back; and that it may be done without disturbing the sleep of the patient, and if this should happen, the bow is made to open by a joint at the summit of it, so as to be instantly disengaged from the neck by the hand of the wearer. ”

“ The spinal column is peculiarly adapted, with its strong ligaments, its cartilage cushions, its perfect flexibility and flexuousness, to withstand jars and shocks. Yet the spine is the door by which disease enters the organism. ”

“ The first of the three dorsal spines is very strong, roughened in front like a file, and hollowed out behind to receive the second much smaller spine, which, besides, has a projection in front, at its base, fitting into a notch of the first. Thus these two spines can only be raised or depressed simultaneously, in such a manner that the first cannot be forced down unless the second has been previously depressed. ”

“ When the spines on being gently stimulated bend towards the point of stimulation, this is due to the contraction of the muscles on the side towards the point of stimulus, for if the superficial plexus of nerve-fibres be cut through so that the stimulus has to pursue a round-about course the spine will bend towards the direction from which the stimulus comes. The bending of the spines away from the stronger stimulus is likewise due to the muscles on the side towards the stimulus. ”

“ The vertebræ, or joints of the spine, are excavated at each end in a conical cavity; the hollow thus formed between every joint and its neighbour is filled with a jelly-like substance, which is continuous through the whole spine, by means of a hole pierced through the centre of each vertebra. There is no true spinal marrow. ”

“ A spinal tube is formed in the external skin of the back, and from this first comes a simple spinal cord without brain, such as we find to be the permanent psychic organ in the lowest type of vertebrate, the amphioxus. ”

“ Now, the spine was not only to furnish the main trunk for the passage of the medullary substance from the brain, but to give out, in the course of its progress, small pipes therefrom, which, being afterwards indefinitely subdivided, might, under the name of nerves, distribute this exquisite supply to every part of the body. ”

“ The spine, on the top of which the head is articulated, is a highly-­flexible column, capable of moving in any direction which may be necessary, and during its movements forming a series of elegant curves, so truly described by the ancients as the serpentine line of beauty ”

“ In accord with this fact it will be observed that9 the foramen or hole in the base of the skull through which the spinal cord passes is adjusted closer and closer to the centre of the base of the skull as the spine becomes erect. In man, whose spinal column is erect, the hole is in the centre of the base; in the reptile, whose spine is horizontal, the hole is at the extreme end of the base. In the ape the spinal axis is at an angle with the vertical line, and the plane of the face conforms to a similar one. ”

“ The complete erection of the spine means that the skull, instead of being suspended in front, is now poised upon the top of the spinal column. The field of vision is enormously enlarged, and it is possible to sweep a great extent of horizon at a moment's notice. ”

“ The spine is, in fact, a long narrow causeway, made of large stones, set like the vertebræ of some huge animal. They form a ridge sloping off in an angle at each side, which is continued downwards with an arrangement of smaller stones, suggestive of ribs. ”

“ Mobility of the spine is of first importance, for in health there is motion between adjacent vertebrae. Lack of movement may be caused by muscular tension, by stretching of ligaments, or by a union of the parts due to bony deposit. ”

“ Between the two posterior radii on the oral surface there is a space with specially arranged spines called the plastron or sternum. The interambulacral plates composing this region are very much lengthened, and interdigitate with one another at the sutures. To this lengthening is due the apparent forward shift of the mouth. The spines are very characteristic, and are very different from any which have as yet been described. They are the sole organs of locomotion. ”