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weight of the animal is horne upon them; and the hocks behind, because they are the propelling power.
It is remarkable in cases of lameness, that when the disease is seated in the feet, the lameness becomes temporarily aggravated on work; whereas if it proceed from disease in the legs, it becomes apparently less after the limbs have been worked a while. With regard to animals keeping their condition while labouring under lameness, experience has taught me that horses lame in the fore feet will, if able to work at all, continue to do so without apparently losing condition from the fret of lameness; but when the hind legs are the seat of disease, the condition evaporates very rapidly. This, I imagine, is because an animal lame in the fore feet will lie down and take more rest than when sound; whereas if lame behind, he will not take sufficient rest, as rising and lying down cause him pain; hence he continually stands, and, of course, aggravates the disease.
The foot is thus sectionised and described by Delawere P. Blaine, Esq.:—
"On examining a perpendicular section of the foot and pasterns, there appear the coffin-bone (a), the navicular or nut bone (6), the coronary or little pastern bone (c), the large pastern bone (d), the back sinew or great flexor tendon of the foot (e), the same tendon sliding over the navicular bone (/), its termination or insertion into the bottom of the coffin-bone («), the elastic matter of the sensible frog (h), the insensible or horny frog (i), the horny sole (k), which includes the parts of the sensible foot; the outer wall of the hoof (I), the elastic processes (m), the attachment of the extensor tendon to the coffin-bone (n), and its attachment to the coronary bone (o), which completes the section.
"The coffin-bone (a) adapts itself to the figure of the hoof, or rather is adapted by nature to this eligible form. The eminence in its front receives the insertion of the tendon of the great extensor muscle of the foot. This important muscle has its upper attachment to the humerus or arm-bone, where it is principally fleshy; but as it passes downwards it becomes tendinous, expanding over every joint, both to prevent friction and to embrace and give firm attachment to each bone with its opposed bone, by which a firm connection of the various parts is maintained, and a simultaneous movement of the whole limb is effected. In the hinder limb this extensor tendon and its two less or tendinous adjuncts arise from the tibia, and in part from the femur, but in their origin are fleshy.
"In the sides of the coffin-bone are attached lateral cartilages, and around its surface are marks of the attachment of the laminated substance.
"The coronary, or small pastern bone (c), is seen to rest on the coffin-bone (a), with which it articulates by its lower end; its posterior part also may be seen to be closely articulated both with the coffin and with the I
navicular or nut bones (/), whose attachments to them are effected by ligaments of great power and some elasticity. Nor is it possible to view this horny box and its contents without being struck with the admirable display of mechanism and contrivance which meets our eye. We are apt to say, 'as strong as a horse,' and some of us use horses as though they were made of imperishable stuff; but surely, when we well consider the subject, we shall see both the necessity and the morality of using them with discretion."
This description of the structure of the foot will probably better enable the uninitiated to understand the seat and nature of various ailments of that part of the horse which are here touched upon.
Blaine further describes the construction of the hoof thus:—
"The hoof itself is conical, or rather, as Clark observes, slightly truncated, and is a secretion as well from the vascular parts of the foot as from the skin, as our nails are formed from the portion of skin called quick. The structure of the hoof is firm and fibrous. Externally it is plane and convex, but internally concave and laminated. The quarters are the lateral parts. As the horn approaches the heels it becomes soft and is reflected inwards. The heels are parted by the horny
frog (b, fig. 3); and without, the frog on each side the hoof inflects its fibres to form the bars which are seen on the under surface (c, fig. 4). In a healthy foot, fig. 4, tlie heels are round, wide, and smooth (a, a), the frog fully expanded, the bars or binders distinct (c, c), no corns in the usual angle (d), the sole broad and concave (d). In a diseased foot, fig. 3, the heels are high, and drawn together by contraction (a, a), the frog narrow, and filled with fissures from contraction and thrush (6), corn frequently present (d), the sole greatly shortened in its transverse diameter, which is morbidly counterbalanced by the increased heights in the truncated form (c). When the hoof is removed, the sensible or fleshy sole (h, section of foot), above which it immediately lies, presents itself, covering the whole of the horny sole, except so much as is taken up by the sensible frog (h). This part is exquisitely sensible and vascular, and thus we learn why injuries to it from puncture produce such serious effect, and why very slight pressure from contraction of the hoof gives so much pain. The sensible frog and the sensible sole form the insensible frog and sole; but when from pressure, too much moisture, or other causes, the sensible frog, instead of forming horn, secretes pus or matter as in thrush, the structure of the whole becomes injured, and the frog, thus losing its support, gradually wastes and decays. It is therefore evident that no thrush can be entirely harmless, as is erroneously supposed.
"Above the sensible frog is the great flexor tendon, or back sinew, inserting itself into the vaulted arch of the coffin (a, section of foot). This important tendon, arising from its parent muscle above the knee, whose origin is taken from the humerus and ulna, in its passage unites with an assistant flexor, but which latter is principally distributed to the pastern bones, while the perforans, so called because it is perforated by the assistant flexor tendon, is inserted into the vault of the coffin; in the posterior extremities the attachments of these two leading flexors and a smaller lateral one are from the femur and tibia.
"The Sensible Laminw.—Around the surface of the coffin-bone, it has been noticed that there are linear indentations to which about five hundred fibro-cartilaginous leaves are attached. Each of these is received between two of the horny lamellae, which line the interior of the horny hoof; and when it is considered what a vast surface of attachment is formed by these means, the strength of the union will not be wondered at. No common violence can separate these parts, and their use as a spring (for they are extensile) to support the action of an animal at once weighty, strong, and extremely agile, must be apparent.
"The vessels and nerves of the foot are derived from the metacarpal arteries, veins, and nerves, which pass behind the pastern, when the main trunks divide to proceed to each side of the foot, and are ramified from thence throughout. It is a division of the metacarpal nerve on each side of the lesser pastern, or on each side of the larger, as occasion suits, which forms the nerve operation now in vogue as a remedy (?) for navicular disease."
Laminitis, or Fever of the Feet, although generally the result of too long a journey, or any exercise where excessive and continuous concussion has been occasioned to the feet, frequently arises from other causes. It is often what is termed secondary, as one of the