Spin

“ Let us imagine an observer placed above this model, far above the north pole of the earth. He sees the earth rotating against the direction of the hands of a watch, and he finds that it precesses with the hands of a watch, so that spin and precession are in opposite directions. Indeed it is because of this that we have the word "precession," which we now apply to the motion of a top, although the precession of a top is in the same direction as that of the spin. ”

“ By analogy with the spin of a rigid body, the component spin of the fluid in any plane at a point is defined as the circulation round a small area in the plane enclosing the point, divided by twice the area. ”

“ If we have a spinning ball and we give to it a new kind of rotation, what will happen? Suppose, for example, that the earth were a homogeneous sphere, and that there were suddenly impressed upon it a new rotatory motion tending to send Africa southwards; the axis of this new spin would have its pole at Java, and this spin combined with the old one would cause the earth to have its true pole somewhere between the present pole and Java. ”

“ S represents the spin-momentum of the fly-wheel at a given instant, S'represents the spin-momentum at a later instant, ΔS represents the increment of spin-momentum, and the arrow T represents the torque which must act upon the fly-wheel shaft. ”

“ In checking up a body rotating contrary to the general consensus of spin, its first effect is to start to turn the axis over. For the body is in dynamical unstable equilibrium with regard to the rest of the system. The righting would continue, practically to the exclusion of any diminution at first of the spin, until the body had turned over in its plane so that the spin became direct. ”

“ Spin′nery, a spinning-mill.—adj. Spin′ning, used in spinning.—ns. Spin′ning-house, a place of correction where lewd and incorrigible women were made to spin; Spin′ning-jenn′y, a machine by which a number of threads can be spun at the same time; Spin′ning-mill, a factory where thread is spun; Spin′ning-wheel, a machine for spinning yarn, consisting of a wheel driven by the hand or by a treadle, which drives one or two spindles.—Spin a yarn, to tell a long story; Spin out, to prolong tediously. ”

“ Excellent examples of the effect of spin on the flight of a ball in the air are afforded in the game of base ball; an expert pitcher by putting on the appropriate spins can make the ball curve either to the right or to the left, upwards or downwards; for the sideway curves the spin must be about a vertical axis, for the upward or downward ones about a horizontal axis. ”

“ You will find that nearly any rounded stone when spun will get up in this way upon its longest axis, if the spin is only vigorous enough, and in the very same way this spinning top tends to get more and more upright. ”

“ When a body, like the ball at the end of the string, revolves in a circle, the centre of the circle is called the centre of its motion, and the body is said to revolve in a plane; because a line extended from the revolving body, to the centre of motion, would describe a plane, or flat surface.
When a body revolves round itself, as a ball suspended by a string, and made to spin round, or a top spinning on the floor, whilst it remains on the same spot; this revolution is round an imaginary line passing through the body, and this line is called its axis of motion. ”

“ A demonstration, depending on the elementary principles of dynamics, of the exact conditions required for the axis OC′ of a spinning top to spin steadily at a constant inclination θ to the vertical OC, is given here before proceeding to the more complicated question of the generalElementary demonstration of the condition of steady motion. motion, when θ, the inclination of the axis, is varying by nutation. ”

“ The spinal cord serves as a conductor of sensation and of motor impulses, and it also plays the part of a brain for those structures of the body which lie below the head. It gives off nerves like streamlets. ”

“ The motion of a sphere, rolling and spinning in the interior of a spherical bowl, or on the top of a sphere, is found to be of the same character as the motion of the axis of a spinning top about a fixed point. ”

“ The spinal cord works automatically and it doesn't wear itself out. The brain tires if it uses its energy.
In walking you use the thought and the brain impulse to start the magneto then the spinal cord action is automatic. ”

“ The best test for skill in ordinary spinning, is to take a long difficult shape, after being finished, and saw it in two lengthwise, and if the variation in thickness is less than 25 per cent of the original gage, it is good practice. ”

“ When not spinning you see that it falls down at once, I find it impossible to balance it on its peg; but what a very different object it is when spinning; you see that it not only does not fall down, it offers a strange resistance when I strike it, and actually lifts itself more and more to an upright position. Once started on scientific observation, nature gives us facts of an analogous kind in great plenty.
Those of you who have observed a rapidly moving heavy belt or rope, know that rapid motion gives a peculiar quasi-rigidity to flexible and even to fluid things. ”

“ In the spinal animal, in response to specific stimuli, various movements are elicited which though of a purposive character are effected, as has been so admirably worked out by Sherington, by complex spinal mechanisms of a reflex character. ”

“ In other words, the spine is a bodily structure as old as the rock-ribbed hills. It has stood the test of time, and therefore must be regarded as the most highly perfected mechanical structure in the body. ”

“ It has been ascertained that compared with the velocity of light and electricity, the velocity of thought is astonishingly small. If I touch the skin of an adult’s leg, it takes no less than about one third of a second before the sensation is reported by the spinal cord to the brain,—the central organ of consciousness; whereas in the same time light will travel over more than fourteen thousand geographical miles; electricity, conducted by a copper wire, nearly thirty-one thousand miles. ”

“ In relation to the brain, the spinal cord is a great mixed motor and sensory nerve, but, in addition to this, it is also a distinct nervous centre, in which originate and terminate all those involuntary impulses which exert so potent an influence in the preservation and economy of the body. ”

“ Spines slightly curved, three-sided prismatic, with two to three verticils of short curved branches. The vertical apical spine is about twice as long as the three basal spines, and connected with them by an irregular loose framework. ”

“ For instance, one of the cases which we can observe is, that where rotatory motion is continued for a very long time, and where the velocity very slowly diminishes, as the motion of a wheel or spinning top. ”

“ The white fibres of the spinal cord consist of collections of nerve filaments, each of which carries on a special work in the transmission of nerve impulses to and from the brain. Each nerve arises from two roots, a motor and a sensory root. ”

“ The spinal cord is not only the seat of reflexes whose "centres" lie wholly within the cord itself; it supplies also conducting paths for nervous reactions initiated by impulses derived from afferent spinal nerve, but involving mechanisms situate altogether headward of the cord, that is to say, in the brain. Many of these reactions affect consciousness, occasioning sensations of various kinds. In regard to the part played by spinal conduction in subserving these sensual reactions a question of practical rather than theoretical importance has been as yet the chief aim of inquiry. ”

“ I suppose we knit and gossip with the spinal cord; indeed we may sing and pray, not with our hearts, nor with our brains, but with the upper part of our spinal cords. We tip our hats to each other, not with our brains, but mainly with our spinal cords ”

“ If so, you need not be told what sort of a place it is. I remember very well how I felt the first time I went into a spinning room. What a whirl of little wheels and great wheels, of bobbins and spindles, of drums and cylinders, there was in that room. My brain seemed to go round with the [112] wheels; and I could hardly help holding my head with both hands, to keep it in its place. ”

“ And now, if you doubt my statement, just ask a child whether its hoop is more likely to tumble down when it is rapidly rolling along, or when it is going very slowly; ask a man on a bicycle to go more and more slowly to see if he keeps his balance better; ask a ballet-dancer how long she could stand on one toe without balancing herself with her arms or a pole, if she were not spinning; ask astronomers how many months would elapse before the earth would point ever so far away from the pole star if it were not spinning ”

“ To accomplish a true reflex movement, a whole mechanism is necessary, set up in the spinal cord or the medulla. To choose voluntarily between several definite courses of action, cerebral centres are necessary, that is, crossways from which paths start, leading to motor mechanisms of diverse form but equal precision. ”

“ The motions of our own bodies are attended by the vibrations peculiar to pressure, and muscular contraction; of other bodies which touch our own, by those from pressure. We judge of rest by the absence of these. Distance is judged of by the quantity of motion, and figure by the relative quantity of distance. And thus it appears, that all degrees and kinds of these tangible qualities may impress corresponding vibrations upon those regions of white medullary substance of the brain, and spinal marrow, which correspond to the skin and muscles. ”

“ 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 Spinal Cord.—The spinal cord proceeds from the base of the brain downward about eighteen inches through a canal provided for it in the vertebræ of the spinal column. It is composed of white matter on the outside, and gray matter within. ”

“ The spinal cord, like the brain, consists of gray and white matter, but the arrangement differs. In the brain the white matter is within, and the gray matter is on the surface. In the cord the gray matter is arranged in two half-moon-shaped masses, the backs of which are connected at the central part. The white matter, consisting mainly of fibers, running for the most part in the direction of the length of the cord, is outside of and surrounds the gray crescents. ”

“ It is a long mass of nerve tissue, branching off at the several vertebrae to nerves communicating with all parts of the body. The Spinal Cord is like a large telephone cable, and the emerging nerves are like the private wires connecting therewith. ”

“ Four equatorial spines one and a half times as long and three times as broad as the sixteen others; all twenty spines cylindrical, of equal breadth throughout their whole length, with simple conical apex; each spine crossed in the distal third by two opposite, simple, conical apophyses. ”

“ Here is one now spinning very quickly, and if I put it horizontally with one end of the axis on a stand, it will not fall down, as it would if it were not spinning, but simply goes round and round. Its weight tries to make it fall, but can only make it turn round. And if we try to lift the end of the axis, we only make it turn round the other way. ”

“ Of course the natural state of the spine, as the seat of a great nervous centre, affects many muscles of the body, and, on the other hand, the freedom of these muscles reacts favorably upon the spine. ”

“ The Vril-ya ignorance of the behaviour of spinning bodies existing as it does side by side with their deep knowledge of magnetism, becomes even more remarkable when it comes home to us that the phenomena of magnetism and of light are certainly closely connected with the behaviour of spinning bodies, and indeed that a familiar knowledge of the behaviour of such bodies is absolutely necessary for a proper comprehension of most of the phenomena occurring in nature. ”

“ People now go to watch a cricket match, not for the sake of seeing a fair duel between bowler and batsman, a close finish, or a decisive result, but merely a batting spectacle. Fast bowlers get worn out prematurely, and are driven to banging the ball down in the hope of the batsman giving catches in the slips; while slow bowlers, in the attempt to bring about impossible breaks, sacrifice length, direction, and spin. The field grows weary, and cricket, instead of being a grand game, becomes a toil and a weariness. ”

“ The general idea of the relations of the brain and spinal cord is that the brain commands and the cord obeys. The brain requires such or such a movement, and the cord, working unconsciously, coördinates the elementary and individual movements required to produce the desired effect. ”

“ The spinal nerves consist of thirty-one pairs, which branch out from the spinal cord. Each pair of nerves contains a right and left member, distributed to the right and the left side of the body respectively. ”

“ 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 result is that the axes of the attracted spheres are given a wobbling movement, such as we may note in the spinning top, though in the toy the cause of the motion is not that which we are considering. ”