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
E. The Blood-Vessels and Nerves.
Vessels which carry blood from the heart to the tissues are called arteries, while those which return the blood to the heart from the tissues are called veins. Arteries and veins are connected by very small, thread-like vessels called capillaries, which originate in the smallest arteries and are so minute that they can not be seen without the aid of a microscope. The capillaries penetrate the soft tissues in every direction, and finally unite to form small veins. For our purpose we need consider only the arteries and veins.
The arteries carrying blood from the heart ramify and subdivide in all parts of the body, and thus reach the foot. They are thick-walled, very elastic tubes, without valves, and carry bright-red blood, which flows in spurts, as can be seen when an artery is cut. If a finger be pressed lightly over an artery lying near the surface, the blood-wave can be felt as a light stroke (pulse). The character of the pulse is important, because in inflammations of the pododerm or horn-producing membrane of the foot we can ascertain by feeling that the pulse is stronger than usual in the large arteries carrying blood to the inflamed foot.
On either side of the phalanges below the fetlock-joint there lies an artery called the digital artery (Fig. 25, a). The pulse can be felt in it as it passes over the fetlock at A, Fig. 25. It gives off the following collateral (side) branches: 1. The artery of the first phalanx (perpendicular artery), with anterior and posterior branches. 2. The artery of the plantar cushion, which supplies with blood the plantar cushion, the velvety tissue of the sole and frog, the bar portion of the coronary band, and the sensitive laminae of the bars. 3. The coronary artery, which carries blood to the coronary band, os coronae, ligaments of the coronary and pedal joints, flexor tendons, and skin.
The terminal branches of the digital arteries are the preplantar and plantar ungual arteries. The preplantar artery passes through the notch in the wing of the os pedis, then along the preplantar fissure, splitting up into many branches, which spread over and penetrate the porous surface of the os pedis. The plantar artery courses along the plantar fissure, enters the plantar foramen, and passes into the semilunar sinus of the os pedis, where it unites with the terminal branch of the opposite digital artery, forming the semi-lunar arch.
After the arterial or pure blood passes through the capillaries it is collected by the veins, to be returned to the heart; then it is driven to the lungs for purification, and is again returned to the heart, from whence it is pumped through the arteries to all parts of the body.
The veins are more numerous than the arteries; they have thinner walls, and the larger ones are provided with valves that prevent the impure blood from flowing backward. The veins carry impure or dark-red blood towards the heart, and if one is opened the dark blood flows in a steady stream; it does not spurt. The great number of veinlets in the lower parts of the foot form a complex net-work (plexus) of vessels which are in such manifold and close union with one another that checking the flood in one part does not seriously interfere with the flowing of the blood towards the larger veins. The following are the most important of these net-works of veins or veinous plexus: (1) the solar venous plexus (Fig. 26, D); (2) the podophyllous venous plexus (Fig. 25, C); (3) superficial coronary venous plexus (Fig. 25, B); (4) bulbar venous plexus (Fig. 26, B). All these plexus of small veins contribute to form the digital veins (Fig. 25 and 26, A).
Nerves are roundish white cords which come from the brain and spinal cord; they generally accompany arteries. They divide and subdivide into smaller and smaller branches till they become invisible to the naked eye and are lost in the tissues. The nerves that are found in the foot come from the spinal cord, and because the largest nerves of the foot accompany the digital arteries they are called digital nerves (Fig. 25, 1). The branches ramify throughout all parts of the foot except the horny box and the hair. Nerves, according to their use or function, are classed as motor and sensory. The motor nerves end in muscles which they stimulate to action and control. The sensory nerves terminate in the skin and in the soft tissues just under the horny box or hoof (pododerm), and render these parts sensitive; that is, they convey certain feelings, as, for example, the pain caused by bruising, pricking, or close-nailing, to the brain and consciousness.
F. The Protective Organs of the Foot
The protective organs are the skin and the horny box or hoof.
The external skin, or hide, covers the entire body; in the feet it covers the bones, tendons, and ligaments, even passing in under the hoof and directly covering the os pedis. This portion of the skin, enclosed by the hoof and therefore invisible, is called the pododerm or foot-skin. In Germany it is called the hoof-skin (huflederhaut), because it is a continuation of the outer visible skin, and because it secretes the hoof – that is, the hoof is produced by it. That part of the skin which is covered with hair is known as the external or hair-skin.
(a) The hair-skin (Fig. 27, a) consists of three superposed layers – (1) the external superficial layer, or epidermis; (2) the middle layer, derm or leather-skin (so-called because leather is made from it); (3) the internal layer, or subcutaneous connective tissue.
- The external layer, or epidermis, is composed merely of single flattened, horn-like cells (scales) lying side by side and over one another, and uniting to form one entire structure – a thin, horn-like layer, without blood-vessels or nerves. It extends over the entire surface of the body, and protects the underlying, very sensitive middle layer from external influences. The oldest cell-layers lie on the outer surface, and are being continuously brushed off in patches or scales, while new ones are constantly being formed on the outer surface of the middle layer.
- The middle layer, leather-skin or dermis, is composed of solid, fibrous, and elastic tissues, and contains many blood-vessels, small nerves, sweat- and oil-glands, and hair follicles from which the hair grows. The hair upon the posterior surface of the fetlock-joint is usually long and coarse, forming a tuft known as the “footlock,” which encloses a horny spur, called the ergot. Common bred horses have, as a rule, larger and coarser footlocks than thoroughbreds. The derm or leather-skin, which produces the hair and epiderm, is the thickest and most important layer of the skin.
- The inner layer, or subcutaneous tissue, unites the middle layer with the muscles, tendons, ligaments, bones, or other structures. It is that loose fibrous mesh or net-work through which the butcher cuts in removing the hide from the carcass.
(b) The hoof-skin (Figs. 27 and 28, b, c, d), or pododerm, is completely enclosed by the hoof. Although it is only an extension of the derm or middle layer of the hair-skin, it differs from the latter in structure and relations.
In order to study the pododerm we should not wrench the hoof off with violence, but should allow the foot to partially decompose by leaving it for six to eight days at ordinary room temperature; it can then be removed without injuring the pododerm. After the hoof has been removed the entire pododerm presents a more or less dark-red color (flesh-color), which is due to the great number of blood-vessels that it contains. For this reason different parts of the pododerm have received the prefix “fleshy,” as for example, fleshy wall, fleshy sole, fleshy frog, etc. The pododerm is what the uninformed horseshoer calls the “quick.” I will here remark that the three layers of the external or hair-skin are represented in the foot; however, the epidermis is in an entirely different form – namely, the horny box or hoof. The internal layer or subcutaneous tissue of the hair-skin is absent in those parts of the foot where the pododerm covers the os pedis. There remains, therefore, only the middle layer, derm, or pododerm, which secretes the hoof, and which is the prolongation and representative of the middle layer of the hair-skin. The pododerm is distinguished from the derm of the hair-skin chiefly by the absence of hairs, oil- and sweat-glands, and the presence on its outer surface of fleshy, sensitive laminae and small thread-like projections called villi.
The pododerm consists of five different parts: the perioplic band, the coronary band, the sensitive laminae (podophyllous tissue), the velvety tissue of the sole, and the velvety tissue of the fleshy frog.
1. The perioplic band (Fig. 28, b) is a narrow ridge, about one-fifth to one-fourth or an inch wide, lying between the hair-skin and the coronary band. Somewhat broader at the toe than on the sides, it broadens out near the bulbs of the heels, over which it passes to end in the velvety tissue of the fleshy frog. It is separated from the coronary band by a narrow depression called the coronary furrow (Moeller). The surface of the perioplic band glistens faintly, and is thickly studded with numerous thread-like projections called villi, which are from one twenty-fourth to one-twelfth of an inch in length. The perioplic band secretes the soft horn of the perioplic ring and the perioplic or varnish-like outer layer of the wall.
2. The coronary band (Fig. 27, c) lies between the perioplic band and the sensitive laminae or fleshy leaves. It presents a prominent convex band or cushion about three-fourths of an inch wide, which extends entirely around the foot from one bulb of the heel to the other. In front it directly covers the anterior extensor tendon of the toe, and at the sides the lateral surfaces of the os coronae and the upper part of the lateral cartilages, while farther back towards the heels the lateral cartilages project considerably above both coronary and perioplic bands. The coronary band is more convex (rounded) in front than on the sides of the foot, and is flattened in the region of the bulbs of the heels. Its surface is thickly covered with villi, which are longer and stronger than those of the perioplic bands. At the bulbs of the heels the coronary band turns forward and inward along the fleshy frog nearly to its summit. This portion of the coronary band is from one-third to one-half an inch wide, and is called the bar portion of the coronary band. It is also covered with villi, which are directly continous with those of the fleshy frog. The coronary band secretes the principal part (middle layer) of the horny wall of the hoof, including the bar portion (bars) of the wall.
3. The fleshy wall, or podophyllous tissue (Figs. 27, 28, d, and 29, a), is all that portion of the pododerm on which there are fleshy leaves. This leafy tissue covers the anterior surface of the os pedis and the lower portion of the external surface of the lateral cartilages. At the bulbs of the heels it turns inward at a sharp angle and extends forward and inward between the bar portion of the coronary band and the posterior part of the velvety tissue of the sole, nearly to the middle of the solar surface of the foot, to form the laminae of the bars (Fig. 29, a). The fleshy wall and fleshy bars are not covered with villi, but with numerous prominent, parallel, fleshy leaves placed close together, each of which runs in a straight line downward and forward from the coronary band to the lower border of the os pedis. Between the fleshy leaves are deep furrows in which, in a foot which has not been deprived of its horny capsule, lie the horny or insensitive leaves of the wall. The fleshy leaves (podophyllous laminae) are related to one another somewhat as the leaves of a boot; their posterior borders are attached to the body or basement membrane of the fleshy wall, while their anterior borders and sides are free. At their upper ends immediately below the coronary band the leaves are quite narrow, but they gradually increase in width down to the middle, and thereafter maintain that breadth to the lower border of the os pedis, where they terminate in free, fleshy villi, which differ in no respect from those of the fleshy sole. The number and length of the fleshy leaves vary; in a medium-sized foot there are about five hundred, while in a large foot there may be as many as six hundred. On the anterior surface of the os pedis the leaves are thickest and longest; on the sides and quarters they gradually decrease in length, while in the bar region they are the shortest and gradually disappear near the anterior ends of the bars. The width of the leaves decreases as they become shorter. Viewed with the naked eye the leaves appear flat and smooth, but under the microscope one can see on both sides of a fleshy leaf numerous small, fleshy leaflets parallel to one another and extending lengthwise with the larger leaf. The large ones are called principal leaves, and the small ones are known as collateral leaves, or simply as leaflets.
The fleshy leaves (podophyllus tissue) secrete the horny leaves (keraphyllous tissue) and serve to bind the horny wall to the pododerm. The strength of this union is due largely to the dovetailing of the horny leaves and their leaflets with the fleshy leaves and their leaflets.
4. The fleshy sole or velvety tissue of the sole (Fig. 29, b) is that part of the pododerm which covers all the under surface of the foot except the plantar cushion, the bar laminae, and the bar portion of the coronary band. It is sometimes slate-colored or studded with black spots, but is usually dark red. It is thickly set with villi, which are especially long and strong* near its periphery. The fleshy sole covers the solar plexus, or net-work of veins, and secretes the horny scale.
*In order to see the length, thickness, and abundance of the villi of the pododerm, place the foot deprived of its hoof in a clear glass jar and cover it with water, renewing the latter until it is no longer tinged with blood.
5. The velvety tissue of the frog (Fig. 29, c) covers the lower surface of the plantar cushion, and in the region of the bulbs (e) passes insensibly into the perioplic band. In comparison with the fleshy sole, it has much finer and shorter villi and contains fewer blood-vessels. It secretes the soft, horny frog.
(c) The horn capsule or hoof (Fig. 30) is the entire mass made up of the horn-cells secreted from the whole surface of the pododerm, and next to the shoe is the organ with which the horse-shoer has most to do. The horn capsule or hoof is nothing more than a very thick epidermis that protects the horse’s foot, just as a well fitting shoe protects the human foot. The hoof of a sound foot is so firmly united with the underlying pododerm that only an extraordinary force can separate them. In its normal condition the hoof exactly fits the soft structures within it; hence it is evident that local or general contraction of the hoof must produce pressure on the blood-vessels and nerve-endings of the pododerm, disturb the circulation of the blood and the nutrition of the foot, and cause pain.
The hoof is divided into three principal parts, which are solidly united in the healthy foot – namely, the wall, the sole, and the frog. That part of the hoof which is almost wholly invisible when the foot is on the ground (Fig. 30, b, c), and which protects the foot in front and upon the sides, is known as the wall. In position, course, direction, and arrangement of its parts it simulates the different parts of the pododerm from which it is developed. It extends from the edge of the hair just above the coronary band to the ground; backward it gradually decreases in height (length), passes around the bulbs of the heels, and turns forward and inward (Fig. 32, d, e, and 34, a, b) to form the bars, which are finally lost in the edge of the sole near the summit of the frog. It thus forms at each heel an angle (Fig. 31, d, and 32, d) known as a buttress, which encloses a branch of horny sole. Externally the wall is smooth, covered with the varnish-like periople, and presents indistinct ring-like markings (Fig. 30). Its inner surface, on the contrary presents a great number of horn-leaves which are spoken of collectively as the keraphyllous tissue (Figs. 32, g, and 35, f). The upper or coronary border of the wall is thin and flexible, and on its inner aspect is the coronary groove, into which fits the coronary band (Fig. 30, f). The lower border of the wall, called the “bearing-edge” or plantar border (Fig. 31, a), is the one to which the horseshoe is fastened. By dividing a hoof from before to behind along its median line, outer and inner halves or walls are produced, and by dividing the entire lower circumference of the wall into five equal parts or sections, a toe, two side walls or mammae, and two quarters will be exhibited (Figs. 32 and 33). In order to designate these regions of the hoof still more accurately, they are spoken of as outer and inner toes, quarters, and heels.
The direction (slant) and length of the wall vary in one and the same hoof, as well as between fore and hind hoofs. The portion of the wall of fore hoofs is the most slanting – that is, forms the most acute angle with the surface of the ground – and is also the longest. Towards the quarters the wall gradually becomes very nearly vertical; in almost all hoofs the posterior part of the quarters slants downward and inward towards the median vertical antero-posterior plane of the foot. At the same time the wall, in passing back from the toe to the heel, becomes gradually shorter in such a manner in that the heights of the toe, side walls, and quarters are related to one another about as 3:2:1 in front hoofs and as 4:3:2 in hind hoofs. The outer wall is, as a rule, somewhat more slanting than the inner. Viewing a foot in profile, the toe and heel should be parallel; that is, the line from the hair to the ground at the toe should be parallel to the line from the hair to the ground at the buttress. All deviations of the wall from a straight line (outward or inward bendings) are to be regarded as faults or defects.
The thickness of the wall is also variable. In front hoofs the wall is thickest at the toe, and becomes gradually thinner towards the quarters, while in hind hoofs, there is very little difference in the thickness of the wall of the toe, sides, and quarters. The more slanting half of the hoof is always the thicker; thus, for example, the outer wall of a base-wide foot is always longer and more oblique than the inner wall, and is also thicker. According to Mayer, the thickness of the wall at the toe varies from three- to five-eights of an inch, and at the quarters from two to three eighths of an inch. These measurements are dependent upon the size and breeding of the horse.
The horn wall is composed of three superposed layers. These from without to within are: (1) the periople, secreted by the perioplic band. It is very thin, glistening, and varnish-like in appearance, and covers the entire outer surface of the wall except where it has been removed by the rasp, and prevents rapid evaporation of moisture from the horn. (2) The middle or protective layer (Fig. 35, d) is the thickest, strongest, and most important of the three layers; it forms the principle mass of the wall, and is developed or secreted by the coronary band, which fits into the coronary groove. There are in the coronary groove a great number of small, funnel-shaped openings into which project the horn-producing villi or papillae of the coronary band. (3) The inner layer or keraphyllous layer (Fig. 35, f) consists of prominent, parallel horn-leaves lying side by side over the entire inner surface of the middle layer of the wall, and continuing beyond the buttresses to the ends of the bars (Fig. 35, f’). This layer of horn-leaves (keraphyllous layer) has in a general way about the same shape and arrangement as the layer of fleshy leaves (podophyllous layer) which secretes it; for the horn-leaves fit in with the fleshy leaves in such a way that every fleshy leaf is embraced by two horn-leaves, and every horn-leaf by two fleshy leaves (Fig. 36). The keraphyllous layer and the horn of the inmost part of the middle or protective layer are always white, even in pigmented (colored) hoofs.
The horn sole (Fig. 31, f, and Fig. 35, g) is secreted by the velvety tissue of the sole. A sole from which the loose flakes of old horn have been removed is about as thick as the wall. It covers the under surface of the foot, and presents upon its upper surface a convexity which exactly fits into the concavity on the under surface of the os pedis. This upper surface is thickly covered by a multitude of minute funnel-shaped openings for the reception of the villi of the velvety tissue of the sole (Fig. 37). The lower surface of the sole is more or less concave, rough, uneven, and often covered by loose scales of a dead horn. Behind, the sole presents a triangular opening whose borders lie partly in contact with the horny frog and partly with the bars. This opening or re-entering angle divides the sole into a body (Fig. 31, f) and two wings or branches (Fig. 31, f’) The outer border of the sole unites through the medium of the white line with the lower part of the inner surface of the wall – that is, with the keraphyllous layer of the wall. This white line (Figs. 31, g, and 35, h), of so much importance to the horse-shoer, is formed by the horn leaves, and by those short plugs of tubular horn which are secreted by the villi that are always found at the lower ends of the fleshy leaves. The white line may be said to exist wherever the horn-leaves can be discerned upon the plantar surface of the hoof. It not only passes around the conference of the sole from heel to heel, but may be followed forward from the buttresses along the bars almost to the summit of the frog. The horn of the white line is soft, unpigmented (white), and possesses so very little resistance (strength) that it is often found crumbling or even absent in places. The visible part of the white line is usually of a grayish-black color, owing to the working in from below of dirt and liquid manure, and to staining by rust from the nails. The white line is very important, since it serves as the point from which we judge of the thickness of the wall, and because the horseshoe nail should penetrate it.
The frog (Figs. 31, h, 35, k, l, 38, and 39), secreted by the velvety tissue covering the plantar cushion and presenting almost the same form as the latter, lies as a wedge between the bars and between the edges of the sole just in front of the bars, with both of which structures it is intimately united. Its horn is quite soft and very elastic. The median lacuna or cleft of the frog (Fig. 31, l) divides it into two branches (Fig. 31, i), which pass backward and outward into the horny bulbs (Fig. 31, k). In front of the median lacuna the two branches unite to form the body of the frog (Fig. 31, h), which ends in a point, designated the point, apex, or summit of the frog. On the upper surface of the frog, directly over the median cleft of the lower surface, there is a small projection called the frog-stay (Figs. 35, l, 38 and 39, b), which fits into the median cleft of the plantar cushion. Besides, the upper surface of the frog shows many minute openings, similar to but smaller than those of the sole and coronary groove, for the reception of villi. In unshod hoofs the frog, sole, bars, and bearing-edge of the wall are on a level; that is, the plantar surface of such hoofs is perfectly flat.
The minute structure of the horn can scarcely be considered in detail in an elementary treatise such as this is. However, a few of the most important facts are as follows:
If we carefully examine the transverse section of the horn of the wall (Fig. 41), sole, or frog, we will see with the naked eye, though much better with a magnifying glass, many minute points quite close to one another, and greatly resembling the small openings which we have seen in the coronary groove of the wall and on the upper surface of the horny sole and frog. If, now, we examine a longitudinal section of the wall (Fig. 40) or sole, we will see a number of fine, dark stripes which are straight, parallel, quite close to one another, of different widths, are which are separated by bands of lighter horn also of different widths. A thin section or slice of the wall taken at right angles to the direction of these dark lines (Figs. 41) shows us that the minute points that are visible to the naked eye, when held up to the light or moderately magnified, prove to be small openings (Fig. 41, a). Since these openings, shown in Fig. 41, represent the dark lines shown in Fig. 40, because an opening is found wherever there is a dark line, we must regard all dark lines seen in longitudinal sections of wall, sole and frog as hollow cylinders or tubes, though they are not always hollow, but are often filled with loosely adjusted, crumbling, broken-down horn-cells. The dark edges of the openings (a) consist of thick layers of horn-cells (tube-walls). The entire structure is called a horn-tube, and the lighter-colored masses of horn (Fig. 41, b) between the tubes are known as intertubular horn.
With the exception of the horny leaves of the wall and bars, all the horn of the hoof is composed of horn-tubes and intertubular horn.
The horn-tubes of the wall, sole, and frog always run downward and forward parallel to the direction of the wall at the toe – that is, in a direction parallel with the inclination of the hoof as a whole. Although the wall, sole, and frog differ from one another considerably with respect to the size and number of the horn-tubes, the quality of the intertubular horn, and the thickness and strength of the horn-cells, these differences are only of subordinate interest or importance to the horse-shoer; but he who desires to learn more of this matter is referred to the work of Leisering & Hartmann, “Der Fuss des Pferdes in Rücksicht auf Bau, Verrichtungen und Hufbeschlag,” eighth edition, Dresden, 1893. This book also treats of the variations in the quality of hoofs, which is very important for the practical horse-shoer to know. It, furthermore, considers the solidity and strength of the horn of the different parts of the hoof.
With the respect to solidity, two kinds of horn are distinguished – namely, hard and soft horn. The periople, the white line, and the frog are soft horn structures; the middle layer of the wall and the sole are hard or solid horn. The wall, however, is somewhat harder and more tenacious than the sole, for the latter passes off in more or less large flakes (exfoliates) or crumbles away on its lower surface, at least in shod feet, while no such spontaneous shortening occurs in the wall.
Soft horn differs from hard horn in that its horn-cells never become hard and horn-like. It is very elastic, absorbs water quickly, and as readily dries out and becomes very hard and brittle and easily fissured and chapped. With respect to quality we distinguish good and bad horn; the former is fine and tenacious (tough), the latter coarse and either soft and crumbling or hard and brittle. If not dried out, all horn is elastic, though soft horn is more elastic than hard. All horn is a poor conductor of heat.
The relative positions of the various parts of the foot are shown in Fig. 42.
Fig. 43 represents the exterior of a well-formed foot.