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Overview
This easy-to-read text explains the horse as a machine designed for movement. Using different colors in his drawings, the author not only describes with clarity the horse's skeleton and the functions of various muscles, but also creates images that have the power to suggest movement and stress. More than 75 illustrations include accurate diagrams and color illustrations fo the horse's anatomy, as well as meticulously rendered sketches of the entire animal.
Of value to students and teachers of art, this book will also appeal to horse lovers who want a deeper understanding — without having to examine the anatomical complexities of the subject — of why this animal is capable of moving with such grace and speed.
Product Details
| ISBN-13: | 9780486145365 |
|---|---|
| Publisher: | Dover Publications |
| Publication date: | 07/06/2012 |
| Series: | Dover Anatomy for Artists |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 160 |
| Sales rank: | 468,225 |
| File size: | 9 MB |
Read an Excerpt
THE ANATOMY AND ACTION OF THE HORSE
By Lowes D. Luard
Dover Publications, Inc.
Copyright © 2014 Dover Publications, Inc.All rights reserved.
ISBN: 978-0-486-14536-5
CHAPTER 1
The Frame
As the only purpose of an artistic anatomy is to help the artist in the observation of form, it can neglect the intricacies of nerves, veins, arteries and many other organs to concern itself almost exclusively with the bones and muscles — one might say the superficial muscles, if it were not that occasionally muscles that are completely hidden should be studied, because an understanding of their action leads to the better understanding of the action of the muscles that show.
Thus limited, the study of what we may call the mechanical anatomy of the horse is comparatively simple, the more so that a horse can do so few things. Outcry from some reader at this aspersion on a noble animal!
The horse excels indeed in trotting, galloping, jumping, pulling weights and carrying loads; a true title to nobility, for such powers serve the convenience and pleasure of man. Its strength and endurance are prodigious. It can lift itself with the added weight of a rider over a jump and recover safely on landing, and even when mounted can gallop down a free running deer.
But to achieve such amazing feats it needs to be made rather rigid. Consequently though it goes forward so brilliantly it goes backwards moderately, lies down and gets up awkwardly, and generally has to make several clumsy efforts before it can roll over on its back. And this necessary rigidity of its backbone and other parts limits the variety of its possible attitudes, and reduces its scope as a subject for the draughtsman. Think of the bending and twisting powers of a cat.
The Bones
Let us begin our study by looking at the bones, and try to see what is required of the muscles to make them act. Bones and muscles are, of course, interdependent, the bones deciding as it were the points of attachment of the muscles and the directions in which they are to pull; being moulded in their turn by the requirements of the muscles, with twists and channels and knobs, that the muscles may get their required purchase and be able to do their work without interfering with each other.
Look first at that essential principle in the construction of all quadrupeds, the difference in the way in which the body is supported by the fore and hind legs.
Support of the Body
The support of the body by the hind legs is through the direct contact of bone with bone, the head of the femur being fitted into the socket of the pelvis, whereas in front the body is slung, being supported from the underside of the shoulder blade by muscles and tendons attached to the ribs (see skeleton, Frontispiece, and Pl. 5, p. 58).
Such differences in construction are adapted to the special duties of the fore and hind quarters. Thus the force of the hind legs, the chief engines of propulsion, is transmitted without loss through the direct thrust of bone on bone, and the fore legs are able to take up without shock the momentum of horse and rider alighting over a jump because the body is attached to them by slings. It may be objected that a man alights upon legs which are fitted directly into the socket of his pelvis and yet jumps without injury. But the comparison is not quite fair; for his legs both propel and catch him and so are not asked to catch more than they themselves have lifted, as the horse's fore legs are. For a horse's hind legs have a power which far exceeds that of the fore legs, galloping, jumping, pulling depending chiefly upon their action. A comparison of the masses of muscle that work the hind and fore legs makes this clear.
The Feet
Another notable difference of structure is in the feet. The fore legs have hoofs which are larger and rounder than those of the hind feet, being designed to carry more weight, for they have to support the weight of the head and neck in addition to their share of the weight of the body; and the hind feet are narrower and more pointed, the better to grip the ground when galloping and jumping. The front feet too have a wider stance.
Correspondence of Fore and Hind Limbs
Despite the differences, there is a correspondence between the fore and hind legs both in construction and in action (see skeleton, Frontispiece, and Pl. 11, p. 108). The shoulder blade, which transmits the propulsion of the fore limb to the body, slopes forwards and downwards to its junction with the upper arm, as the femur, which conveys the propulsion of the hind limb, does to its junction with the tibia at the stifle joint; the upper arm slopes backwards to the elbow, the 'hock' of the fore limb, as the tibia does to the hock; from which points the legs descend similarly to the pastern and hoof, the hind leg directly, the fore legs with an added joint, the 'knee'. But the knee makes no difference in ordinary paces between the propulsive action of the fore leg and that of the hind leg, as it is maintained unbent; it is in the advancement of the foreleg that the use of the knee comes in, to lift the foot clear of the ground to prevent tripping, and to raise it well out of the way as when jumping.
In a quiet pace such as the walk, the fore and hind legs behave very similarly, serving much like the spoke of a wheel. It is only in violent movements such as galloping and jumping that their differences of action really come out and the purpose of their differences of structure becomes clear.
Often in books of artistic anatomy little or no attempt is made to study the effect of the action and interplay of the different parts, the muscles being merely mapped as flexors and extensors, that is, muscles that close a joint or pull it open. Such classifications, necessary as they are, should be supplemented with some explanation of the movements resulting from the action of muscles when working in combination. And this can best be done, I think, by trying to work out how some particular action is effected.
Action of Muscles
Let us think then not of how a horse shoots his foot backwards as in kicking, but of how from the resistance of the stationary hoof on the ground these same muscles of his leg are used to push him forwards. To think always of his movements in this way is to get, I believe, a better understanding of a horse's action, a better 'feel' of the forces and stresses which create the sequence of shapes and rhythms that the artist enjoys. Let us approach the study of the muscles as an inventor's problem of how best to operate the given levers, the bones, so as to supply the required momentum to the body. Study the skeleton and before you look at the diagrams of the muscles ask yourself what muscles you would design, and you will, I am sure, understand better nature's solution of the problem.
But before studying the muscles, which are reserved for another chapter, let us continue our general survey of the skeleton (see the Frontispiece).
Look at the vertebral column and for the moment that part of it from the hips to the chest which forms the back. The vertebral column, which runs from the head to the tip of the tail, is composed of a series of bones connected by joints, which vary enormously in their construction and their flexibility, the neck bones being deeply embedded one in the other, with ball - and - socket joints, whereas the tail bones are really not socketed into each other at all. This gives such flexibility to the tail that a horse can swish it up and down, sideways or round and round with absolute freedom; and the deep ball and socketing of the neck bones allows for the pull of strong muscles without any danger of dislocation. In the backbone the vertebrae are firmly connected without much play, so that it may be a firm though not rigid column.
The Vertebral Column
The horse's power of carrying weight depends upon this firm knitting of the bones of the back, to which the slight arching of it contributes. The backbone runs up to the pelvis from a point in the middle of the chest where the neck properly begins. And the height of the withers, so characteristic of the shape of a horse, is, we see, not directly due to the backbone, but to the long processes which stand up from it.
The variation in the processes on the different vertebræ is very striking. They are, of course, modified to suit their duties. The long processes that form the withers serve to support the neck and head, and are raked backwards the better to resist this pull. On the loins the upright processes are shorter and blunter (it is the only comfortable place to sit on a bare-backed donkey, with its knife-edged backbone), and are inclined slightly forward: and the transverse processes are very strongly developed into broad flat blades, for the attachment of strong muscles (see illustration, p. 33). Where the pelvis is attached, a section of the backbone is actually rigid, for the vertebrae are welded into a solid mass, called the sacrum; and the sacrum, making a unit with the pelvis, transmits the drive of the hind legs to the body.
The Neck
The neck is not equally flexible in all directions. It moves freely downwards, upwards to a certain height, but not very freely sideways; for the deep entry of the ball of one vertebra into the socket of its neighbour and the large development of their transverse processes check the lateral movement. The two points of its greatest flexibility are near the chest and just behind the head. There the skull is supported by the atlas bone on which it has an up-and-down movement only, the atlas being able to rotate upon the axis bone through about three-quarters of a circle. The flanges on the atlas, necessarily strongly developed for the attachment of the strong muscles that support the head, are very noticeable in the living animal, being indeed the only bone the forms of which show on the surface between the head and the chest.
The Skull
In the skull itself a striking characteristic is the enormous depth of the jaw and maxilla to give the molar teeth deep secure sockets, and the marked ridges of bone on the side of the face for the attachment of the strong Masseter muscles that work it. In a dead horse, or one that is lying down, the head looks almost too large and too heavy to be lifted. It is, however, lighter than it looks, for the skull contains immense hollow chambers, the sinuses, which communicate with the nasal cavity.
The Ribs
The horse has eighteen ribs on each side, of which the strongest are at the chest where they are attached firmly to the breast bone, the first eight ribs receiving the insertions of the branches of the big Serratus muscle (39b) upon which the weight of the body is carried from the shoulder blade. Towards the quarters the ribs are inclined backwards and are thinner and more mobile, allowing play to the lungs and other internal organs.
The Shoulder Blades
A horse has no collar bones, as we have, because they would not serve him. Our shoulder blades are on our flat back and our collar bones keep our arms apart that we may the better use them. A horse is flattened laterally and his shoulder blades, which lie along his chest, move freely forwards and backwards at every stride. If you will look at his skeleton from in front (see illustration, p. 27), you will see that his chest is boat-shaped, so that his shoulder blade in moving forward comes nearer to and brings his foot nearer to the central line of his motion.
There are many constructions and adaptations of shape in the bones, on which I have not touched, to which reference will be made later when treating of the muscles and their action.
And now let us turn from the skeleton to the muscles that work it.
CHAPTER 2Action and Mechanics
I suggested that the best way for the reader to understand the muscles and their action would be to study the bones, and try to invent some of the required muscles for himself. A difficult task, for a horse, like any living thing, is of an intricacy beyond the most ingenious machine ever invented by man.
Man indeed has only surpassed the animals in speed and power by limiting each machine to some special purpose, and he has been anticipated in all his inventions by nature — at least it is difficult to think of anything that he has done the principle of which is not embodied in some creature. There is the eel that stuns with an electrical discharge: creatures in the darkness of the deep sea that light their way with head lamps like a car: the little Indian fish that can shoot at a distance of six feet the insects that flutter overhead with a jet of water, as the naturalist shoots humming birds: there is a fish too that has a rod and line with hooks, with which he grapples and stroke-hauls his prey: in the eye there is a muscle that changes the direction of its pull by working through a ring as its pulley: the bird's wing is both plane and propeller; and the aeroplane that does not lift its wheels and carriage wears 'trousers', to break the air resistance, as the eagle wears feathers on his legs: and the horse's leg, when on the ground, works like the spoke of a wheel — which brings us back to our subject.
Automatic Support
In our study of the muscles let us begin with the legs, as we did in studying the bones. When a horse is standing still, as in stable, he remains planted firmly on both his fore legs for a long time without altering his position, but is continually shifting the weight of his quarters from one hind leg to the other. The reason for this is that his forehand is entirely supported by inelastic tissues, whereas his quarters are supported partly by muscular force, so that he is compelled frequently to change his position to rest his muscles. If a horse does not stand planted equally on both fore feet, but eases one of them, it is a sure sign that he has some soreness or inflammation in the limb.
The weight of the fore part of the body is supported from the underside of the shoulder blade by the great Serratus Thoracis muscle (39b), the eight branches of which are attached to the first eight ribs (see Pls. 2, 5 and 11).
Automatic Support
The middle branches of the muscle are interspersed with inelastic fibres which, when the muscle is relaxed, support the body without any fatigue to the horse. The weight of the body pulling on the shoulder blade tends to flex, to close, the joint at A (Pl. 11, p. 108), so here also there is an arrangement of inelastic tissue to keep the joint from closing. The Biceps Brachii muscle (47), which is attached to the shoulder blade at one end and, passing over the humerus, is attached to the radius at the other, could do this work and often does, for it is the extensor of the joint, but it would become exhausted if it had to support the horse all the time, and so it is relieved of this duty by the inelastic tissue which forms part of it.
The only possibility now of the horse collapsing is if his knee, C, were to buckle forward, so another inelastic string is inserted at a point on the cannon bone below the knee. A strong tendinous band, found in the External Radial Extensor (53), it is attached at its upper end to the Biceps muscle (47), so that it is drawn the tighter, the more the latter tightens.
In Pl. 11 the construction is depicted diagrammatically with coloured lines, the Biceps green, the External Radial Extensor mauve, which make it clear, I think, that the cord to below the knee is not only useful for the purpose which has been described, but is indispensable in violent movements such as landing over a jump. For then the greater the pull of the body upon the shoulder blade the greater the tension of this cord and the more firmly the knee is closed against any possibility of buckling over.
Automatic Support
The automatic support of the horse's weight is completed at the fetlock, D, by the Suspensory Ligament (62) and at the pastern joints, E and F, by the tendons of the Perforans (61) and Perforatus (60) muscles with their check ligaments.
The Suspensory Ligament (62) is a broad elastic cord attached at the back of the knee and cannon bone, very visible towards the lower end of the cannon bone; it divides just above the fetlock into two branches which are inserted on the sesamoid bones, a band passing forward on each side of the joint to the front of the first phalanx, to join the tendon of the Common Digital Extensor (54): see Pl. 6, p. 62.
This arrangement serves two purposes. It supports the fetlock automatically, and by its prolongation to the front prevents the pasterns from knuckling over forwards, much as the tie string below the knee prevents the knee from buckling forward.
To test the principle of the automatic support of the horse by his fore legs, I made a rough model with bits of wood and string like this, and found that a weight, W, representing the downward pull of the body, attached as depicted, was supported by my gimcrack construction. So the muscular effort demanded of the front legs when at rest is apparently no greater than the small muscular adjustments we ourselves make, when standing, to keep the jointed column of our legs upright under our body.
The hind leg, as we noticed in Chapter I, corresponds very closely to the fore leg in the general character and relation of the bones; and the correspondence is close, for it is provided with an inelastic string, the Peronaeus Tertius (82), which connects the femur with the cannon bone, much as the Biceps Brachii connects the shoulder blade with the Radius. Yet the hind quarters are not automatically supported without effort on the part of the muscles, since the articulation of the femur with the pelvis falls too far forward in relation to the foot.
(Continues...)
Excerpted from THE ANATOMY AND ACTION OF THE HORSE by Lowes D. Luard. Copyright © 2014 Dover Publications, Inc.. Excerpted by permission of Dover Publications, Inc..
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Table of Contents
Contents
Title Page,Copyright Page,
Preface,
The Skeleton,
Chapter I. The Frame,
Chapter II. Action and Mechanics,
Chapter III. The Skeleton,
Chapter IV. The Muscles,
Chapter V. Proportions,
Chapter VI. Movement,
Chapter VII. Art,
Chapter VIII. Glossary,
Chapter IX. Notes on the Text,
Bibliography,
Index,