A Text-Book of
by A. Lungwitz and John W. Adams, copyright 1897
This is the first part in what will be a complete reprint of Lungwitz & Adams’ important ‘Textbook of Horse-Shoeing’ originally written in the 1880’s and containing some remarkably modern information. This volume goes into the greatest detail on the subject and with a intelligent clarity that belies how old it is. Coming as it did at end of the first horse era, and well before anyone might have reasonably predicted the advent of the automobile and tractor, it is apparent how important the equine was to the whole of society. The authors, of Germany and Pennsylvania, compiled what was, at the time, to be the ultimate word on the subject. As with all of the reprints we have offered over forty years time, we trust that readers will be triggered by these words to complete their education with diligence and introspection. Just because something is old doesn’t always make it right, and of course just because something is new doesn’t make it the true culmination. LRM
A. The Bones of the Foot
Since the horse is useful to man only by reason of his movements, his foot deserves the most careful attention. The horse-shoer should be familiar with all its parts. Fig. 3 shows the osseous framework of the foot, consisting of the lower end of the cannon bone (A), the long pastern (B), the two sesamoid bones (C), the short pastern (D), and the pedal bone (E). The lower end of the cannon, or large metacarpal bone (A) exhibits two convex articular surfaces (condyles) separated by a median ridge running from before to behind, and all covered by articular cartilage. On both the external and internal aspects of the lower end of the cannon are small uneven depressions in which ligaments take their attachment.
The condyles of the cannon articulate with the os suffraginis (long pastern) and the two sesamoids (Figs. 3, C, and 4, B) in such a manner that in the forefeet the cannon makes an angle with the long pastern of from one hundred and thirty-five to one hundred and forty degrees, and in the hind feet of from one hundred and forty to one hundred and forty-five degrees.
The long pastern (first phalanx) (Fig. 4, A) is about one-third the length of the cannon; its upper and thicker end presents two condyloid cavities (a) (glenoid cavities), separated by a median groove, which exactly fit the condyles and ridge at the lower end of the cannon. The lower end of the long pastern is smaller than the upper, and is provided with two condyles, between which is a shallow groove (e). The anterior face of the bone is smooth, rounded from side to side, and blends into the lateral borders. The posterior face is flatter, and shows a clearly marked triangle to which ligaments attach.
The two sesamoid bones (Fig. 4, B) are small, and somewhat pyramidal in shape, and, lying against the posterior part of the condyles of the cannon bone, increase the articular surfaces at the upper end of the long pastern.
The short pastern (second phalanx) (Figs. 5 and 6) lies under the first phalanx and above the os pedis; it is somewhat cubical in shape. Its upper articular surface (Fig. 5, a) presents two glenoid cavities to correspond with the condyles of the first phalanx. The lower articular surface (Fig. 5, d) resembles the lower end of the first phalanx. The upper posterior border of this bone is prominent and prolonged transversely (Fig. 6, a), to serve as a supporting ledge for the first phalanx, as a point of attachment for the perforatus tendon, and as a gliding surface for the perforans tendon.
The lowest bone of the limb is the third phalanx or os pedis (Fig. 7). In form it is similar to the hoof. The anterior or wall-surface (a) is rough, like pumice stone. Above and in front is the pyramidal eminence to which the tendon of the anterior extensor of the phalanges attaches. Behind, the bone extends backward to form the inner and outer branches (c, c) or wings of the os pedis. The upper, articular surface (b) slopes backward and downward. The lower, solar or plantar surface (Fig. 8, a) is slightly concave, and presents posteriorly a half-moon-shaped excavation, with a roughened border called the semilunar crest (c), to which the perforans tendon attaches; just above this crest are two small holes (e) known as the plantar foramina, through which the plantar arteries pass into the bone. The surfaces of wall and sole come together in a sharp edge, which is circular in its course. It is easy to tell whether a pedal bone is from a fore or a hind limb; the os pedis of a hind leg has a steeper and more pointed toe, and a more strongly concaved solar surface than the same bone of a foreleg. Not only is the outline of the sharp inferior border of the os pedis of a front foot more rounded at the toe, but when placed on a flat surface the toe does not touch by reason of being turned slightly upward, much as a shoe designed to give a “rolling motion.” The os pedis of a hind foot is narrower from side to side (pointed), and does not turn up at the toe.
The right and left hoof-bones are also, as a rule, easily distinguished by variations in the surfaces of wall and sole. The shape of the os pedis corresponds to the form of the horny box or hoof, and therefore a knowledge of this bone is absolutely necessary.
The navicular bone (os naviculare, nut-bone, Fig. 9 and 10) is an accessory or sesamoid bone to the os pedis. It is a small bone, transversely elongated and situated behind and below the os pedis and between the wings of the latter. It adds to the articular surface of the pedal joint. Its under surface is smooth, and acts as a gliding surface for the perforans tendon which is quite wide at this point.
The long axes of the three phalanges (os suffraginis, os coronae, and os pedis) should unite to form a straight line, when viewed either from in front or from one side; that is, the direction of each of these three bones should be the same as the common direction of the three considered as a whole.
B. The Articulations of the Foot.
There are three articulations in the foot – namely, the fetlock, coronary, and pedal joints. All are hinge-joints, the fetlock being a perfect hinge-joint, and the other two imperfect hinge-joints. Each has a capsular ligament, and also several funicular or cord-like ligaments which are placed at the sides of (lateral ligaments), or behind (on the side of flexion) the joint.
I. The fetlock or metacarpo-phalangeal articulation is formed by the condyles at the lower end of the cannon bone and the glenoid cavities formed by the union of the articular surfaces of the sesamoids and the upper end of the first phalanx. The following ligaments are about this joints:
- Two lateral ligaments, an external and internal (Fig. 11, a).
- Two lateral sesamoid ligaments (f).
- An intersesamoid ligament (Fig. 12, b), a thick, fibrous mass, binding the sesamoid bones almost immovably together, extending above them and presenting on its posterior face a smooth groove, in which glide the flexor tendons of the phalanges (perforans and perforatus).
- The suspensory ligament of the fetlock (Figs. 11, c, 12, c, and 13, c). This may also be called the superior sesamoid ligament. It is a long and very powerful brace, originating on the lower row of carpal bones (bones of the hock in the hind leg) and on the upper end of the cannon between the heads of the two splint-bones, and dividing at the lower third of the cannon into two branches (c), which are attached one to each sesamoid bone. Below these bones these two branches are prolonged obliquely downward and forward on opposte sides of the lond pastern to pass into the borders of the anterior extensor tendon of the toe at about the middle of the long pastern (Fig. 14, b’).
- The inferior sesamoid ligament (Figs. 11, d’, 12, d, d’, and 13, d’ and E). This originates at the lowest part of the sesamoid bones and intersesamoid ligament and consists of three parts or branches. The median branch (d) is the longest and strongest, and takes its lower attachment in the middle of the fibro-cartilaginous lip found on the upper border of the posterior face of the second phalanx. The two lateral branches (d’) approach each other as they descend, and terminate on the sides of the roughened triangle on the posterior face of the first phalanx.
- The deep inferior sesamoid ligament (Fig. 13, e) is quite short, and consists of a number of distinct, thin fibrous bands lying directly against the bone and entirely covered by the median and lateral inferior sesamoid ligaments. These fibrous bands cross one another in passing from the sesamoids to the first phalanx.
II. The coronary joint is the simplest of the three articulations of the foot. The long pastern furnishes two condyles and the short pastern two glenoid cavities. Besides a capsular ligament there are —
- Two lateral coronary ligaments (k), and,
- Six posterior coronary ligaments, — namely, two superior coronary ligaments (h), two median coronary ligaments (h’), and two inferior coronary ligaments (g).
III. The pedal articulation (“coffin” joint) is an imperfect hinge-joint, and is formed by the condyles at the lower end of the short pastern and the two glenoid cavities in the united upper surfaces of the pedal and navicular bones. Besides the capsular ligament (Figs. 12 and 13, l), which binds all three bones together, there are the following accessory ligaments:
- Two strong lateral ligaments, an external and an internal (Fig. 11, i), whose posterior borders are lost in the lateral cartilages which cover them.
- Two lateral suspensory ligaments of the navicular bone (k). They begin on the posterior border and ends of the navicular bone, and terminate on the lower part of the anterior surface of the os suffraginis, where they are lost in the lateral ligaments of the coronary articulation.
- The lateral ligaments of the lateral cartilages, navicular bone, and os pedis. They are short, and unite the navicular bone with the os pedis and lateral cartilages.
Of the three phalangeal articulations, the pedal is the only one that permits of any lateral movement; hence it is an imperfect hinge-joint.
C. The Locomotory Organs of the Foot.
Though the muscles are the organs which produce motion, the horseshoer need concern himself only with the tendons of those muscles which extend and flex the phalanges. These tendons are either extensors or flexors. The extensors lie on the anterior face and the flexors on the posterior face of the phalanges.
The anterior extensor of the phalanges (Fig. 14, a) extends the long and short pasterns and the hoof-bone; it is broad, and made somewhat broader by receiving the branches of the suspensory ligament (b’) that some from the sesamoid bones. It takes a firm attachment on the pyramidal eminence of the os pedis. In the forefeet the long pastern has a special extensor tendon (c), which is known as the lateral extensor. When the muscles to which these tendons are attached act – that is, when they draw themselves together, or contract as we term this action – the foot is carried forward (extended).
There are two flexor tendons of the phalanges – namely, the superficial (perforatus tendon) and the deep (perforans tendon).
- The superficial flexor or perforatus tendon (Figs. 15, b, and 16, a, b) lies behind, immediately under the skin, and covers the deep flexor or perforans tendon. At the gliding surface between sesamoid bones (Fig. 15, b’) through which the perforans tendon (a”’) passes, while a short distance farther down it bifurcates, or divides into to branches (Figs. 15, b”, and 16, b), which terminate, one on either side, partly on the inferior lateral borders of the first phalanx and partly on the fibro-cartilage of the second phalanx. It acts simultaneously on the long and short pasterns.
- The deep flexor or perforans tendon (Figs. 15, a, and 16, c) is cylindrical and stronger than the perforatus tendon; above the fetlock-joint it lies between the perforatus and the suspensory ligament of the fetlock. At the sesamoid bones it passes through the ring formed by the perforatus tendon (Fig. 15, b’), then becomes broad and double-edged, passes between the two terminal branches of the perforatus, glides over the fibro-cartilage of the second phalanx and over the inferior surface of the navicular bone, and finally ends on the semilunar crest of the third phalanx. In common with the perforatus tendon it flexes the foot.
If a point a few inches above the fetlock a limb be cut through from behind, the knife will pass successively through the following structures; skin, perforatus tendon, perforans tendon, suspensory ligament, cannon bone, lateral extensor tendon, anterior extensor tendon, and lastly, the skin on the anterior surface of the limb. The flexor tendons are frequently thickened and shortened by inflammation due to injury, and as a result the foot is pulled backward and the hoof grandually becomes nearly upright – i.e., stubby, steep-toed. A knowledge of the normal condition of the tendons is, therefore, absolutely necessary to the horseshoer. Both flexor tendons are embraced and held in place by ligaments and fascia passing our from the phalanges (Figs. 16, d’, and 24, e, f). The extensor and flexor tendons essentially contribute to the strong union of the phalangeal bones, and especially to the support and stability of the fetlock-joint. The gliding of the tendons is made easy by the secretion of a lubricating fluid, called synovia, from the inner surface of the sheaths which surround them. In thin-skinned well-bred horses with sound limbs, one can not only distinctly feel the tendons through the skin, but can see their outline. When the tendons and bones are free from all inflammatory thickenings, and the tendon sheaths are not visibly distended, we say that the leg is “clean.”
Mucous Bursae and Tendon Sheaths.
Accessory to the tendons, there are in the foot roundish, membranous sacs (mucous bursae) and membranous tubes (tendon sheaths). Both contain a liquid resembling synovia (“joint water”), which facilitates the gliding of the tendons. These bursae and sheaths are often distended to form soft tumors, known as hygromata (“wind-puffs,” “wind-galls”).
(a) Mucous Bursae. – They lie beneath tendons at those places where the tendons pass over bony prominences.
- The mucous bursa of the anterior extensor tendon of the toe is about the size of a walnut, and lies between the tendon and the capsular ligament of the fetlock-joint (Figs. 17, g, and 18, e).
- The mucous bursa of the extensor tendon of the long pastern (lateral extensor) is somewhat smaller, and lies, likewise, beneath the tendon, between it and the capsular ligament of the fetlock-joint (Fig. 17, h).
- The mucous bursa of the navicular region lies between the under surface (gliding surface) of the navicular bone and the flexor pedis perforans tendon (deep flexor). Its width equals the length of the navicular bone, and it extends upward and downward beyond the bone. Above, it is separated from the sheath of the perforans tendon (“great sesamoid sheath”) by a membranous partition; below, it passes to the attachment of the perforans tendon to the semilunar crest of the os pedis.
(b) There is but one tendon sheath in the foot – the sheath common to the two flexor tendons (great sesamoid sheath). It encloses the flexor tendons from the middle third of the cannon down to the middle of the short pastern, and is intimately united with the flexor pedis perforans tendon (Fig. 17, f, f’, f”, f”’. Fig. 18, d, d’, d”, d”’).
Alerting the Relative Tension of the Flexor Tendons and Suspensory Ligament of the Fetlock-Joint.
The body-weight imposed at the fetlock-joint is supported, in large part, by the suspensory ligament; somewhat less weight is borne by the perforans tendon, and a still smaller amount by the perforatus. The coronary joint is supported chiefly by the perforatus, assisted by the perforans. The pedal joint is pressed forward and upward by the perforans tendon passing in a curve beneath the navicular bone. Each of these three structures bears its normal proportion of the body-weight when the three phalanges, as viewed from the side, form a continuous straight line from the fetlock-joint to the ground. In such a case the obliquity of the long foot pastern will be the same as that of the toe (see Foot-Axis, p. 70.)
Raising the toe by means of a tip, a full shoe with thinned branches or a toe-calk, or pairing away the quarters will tilt the os pedis backward, break the foot-axis backward in the pedal joint and to a less extent in the coronary joint, and increase the tension of the perforans tendon considerable and of the perforatus slightly. These tendons tightening behind the fetlock-joint force it forward, causing the long pastern to stand steeper, and taking some strain from the suspensory ligament. Hence, the perforans tendon is under greatest tension, and the suspensory ligament under least tension, when the foot-axis is broken strongly backward.
Shortening the toe, or raising the quarters by heel-calks or thickened branches, will tilt the os pedis forward, break the foot-axis forward in the pedal joint, and will greatly lessen the tension of the perforans tendon. The aggregate tension of perforans and perforatus tendons being diminished, the fetlock sinks downward and backward, the long pastern assumes a more nearly horizontal direction, and the tension of the suspensory ligament is increased. Thus, the perforans tendon is under least tension, and the suspensory ligament under greatest strain, when the foot axis is broken strongly forward.
D. The Elastic Parts of the Foot.
All bodies which under pressure or traction change their form, but return again to their original shape as soon as the pressure or traction ceases, are called elastic or springy. Nearly all parts of the horse’s foot, except the bones, possess more or less elasticity. The lateral cartilages and the plantar cushion are elastic to a high degree, but the coronary band, the lamince, the articular cartilage, and the horny box or hoof are less elastic. This property of characteristic is possessed by the respective parts of the foot in accordance with their function, location, and structure.
The two lateral cartilages (Figs. 19, C and 20, b) are irregular, quadrangular plates, attached to the wings of the os pedis, and extending so far upward and backward that one can feel them yield to pressure on the skin above the coronet, and can thus test their elasticity. The perforans tendon and the plantar cushion lie between the lateral cartilages, and on the sides and behind are partially enclosed by them. The internal concave surface of the lateral cartilage (Fig. 20) is attached to the plantar cushion, os pedis, the navicular bone, and, like the external, slightly convex surface, is covered with many blood-vessels (veins) (Fig. 25, B).
The plantar cushion (Figs. 21, 22, 23) is composed almost entirely of yellow elastic and white fibrous tissues, with adipose (fat) cells distributed throughout their substance. It is similar in form to the horny frog, and lies between it and the perforans tendon (Fig. 24, a). The bulbs are formed by the posterior thicker portion which lies between the lateral cartilages and is divided into two parts by the cleft or median lacuna (Figs. 21, a, and 23, d). The summit is attached to the plantar face of the os pedis in front of the semilunar crest, and the bulbs are attached to the lateral cartilages. It is covered inferiorly by the velvety tissue of the frog (pododerm).