966 



PRACTICE OF AGRICULTURE. Part III. 



In the ox it is wanting ; in the dog and eat, as requiring numerous motions in their limbs, it is, on the 



™2££F , jJEtdriiil,Or hock ofth, hone (10, 10), is a striking instance of Hie perfect mechanism displayed 

 in the bony structure of thU admired animal it is formed by an assemblage ot six bonea, and (ometimea 

 of seven ■ while in the ox, sheep, and deer, there are Mldom more than five Between these bones there 



an open aiiu'lc with III*- tilna, aim is lar iraiuun m>m mi *• ...... ... ,....., ...... ..... d-— --— ■ --- -• 



anadraneda all the bones, from Hie hock downwards, are much elongated, and form a part of the upright 

 Dillar of the linili In the horse, therefore, the point of the hoek is the true point ol the heel, and, as in 

 the human liu-nrc the great twisted tendons Ot the gastrnciieimi muscles are inserted into it: but the 

 ■imicll ition oftendo vchilles would be too forced here A broad hoek, as already observed m the exterior 

 conformation, may be now still more plainly seen to be very important to strength and speed; for the 

 tenser the calcaneum or heel bone of the hock, the longer must be the lever that the muscles ot the thi^h 

 let'bv • and a very slight increase or diminution in its length must make a very great difference in the 

 nower of the joint It it by this tendon acting on this mechanism, that, when the animal has inclined 

 the ancle between the canon and the tibia, or, in other words, when the extremities arc bent under him 

 in theraUop OX trot, he is enabled to open it again. The bones of the hock, like those of the knee, are 

 united Wether by strong ligamentous fibres; and it is to an inflammation of those uniting the calcaneum 

 and cuboid boms,' that the disease called curb is to be attributed ; and to a similar inflammatory affection 

 of the ligaments in the front of the hocks, that spavin* of the first stage are owing : in the latter stages 

 the periosteum and bones themselves become affected. The remainder of the bones below do not differ 

 so easenti illy from the corresponding bones in the fore extremities as to need an individual description. 

 It lmv however be remarked, that the hinder canon or shank bone is longer than the lore, and that the 

 pastern is also the same, but is less oblique in its situation ; by which wise provision the horse is enabled 

 to elevate and sustain his body entirely on his hinder parts without danger; which would not have been 

 the case if the obliquity of those parts had been considerable. 



Subsect. 4. General Functions of the Bony Skeleton. 



RS29 The tkeletOH of the horse must be considered as a mechanism of admirable wisdom and contrivance, 

 which having considered in detail, we offer the following summary of its functions generally as a whole. 

 It will be found to present nearly a quadrilateral figure, having an inclined cylinder resting on four sup. 

 uortin" pillars The spinal column, as the inclined cylinder, serves as a base for the soft parts, and is 

 found not truly horizontal, but dipping downwards over the forelegs; by which the propelling force of 

 the hinder extremities is relieved by the maximum of strength thus transferred. 1 he increased weight 

 of the hinder part of the cylinder is admirably counterpoised by the head and neck, which are projected 

 forwards • by these means leaving the line of direction near the centre of the whole. The length of a 

 cylinder may be such as not to support its own weight ; Nature, therefore, has limited the length of the 

 spines of animals : hence, ceteribus paribus, a long-backed horse must be weaker than a short one ; and 

 thus likewise, small horses can carrv proportionably more than larger ones. Ihe four pillars which 

 suDu'ort this cylinder are not perpendicular partially ; but they are so totally : lor a perpendicular drawn 

 from their common centre of gravity will be found to fall nearly in their common base, by which means 

 thev are supported as firmly as though their individual axes had been in a line perpendicular to the 

 horizon Had they been perpendicularly opposed to each other, there could have been but little elas- 

 ticity and consequent ease in motion ; every exertion would have proved a jar, and every increased effort 

 would h-ive produced luxation or fracture. To increase our admiration ot this mechanism, we need only 

 turn our attention to the contra-disposition of these angles in the fore and hinder supporting pillars. 



the various bony portic... 



muscles • and wherever the angles are found most extensive, the muscles will be found proportionally 

 Btrone and large This muscular exertion, to counterbalance the angular inclination, occasions fatigue; 

 as the set of muscles immediately employed becoming weary, the animal is obliged to call another set into 

 action which change is necessarilv more or less freqnent as the animal is weaker or stronger. 



6A3l' The extent of the action of the bony portions of the extremities is the produce ol the length and 

 direction of the various parts entering their composition, and of the different angles they are capable of 

 forming- as progression itself is effected by these angles closing, and suddenly extending themselves 

 a-ain The force of the action arises from the direction of the component parts of the ankles, in combin- 

 ation with the agency of the muscles. The repetition of the action is dependent on the muscles alone ; 

 but as the original action arose out of the length and direction of the parts, so it will be evident that in 

 every subsequent repetition, it will be more or less extensive, as these are more or less perfect in their 

 formation even though the muscular exertions should be the same; thus, some strong animals cannot 

 mote so fast as others with less strength, as the cart-horse and racer, or greyhound and mastiff: 



6o3" The bony mechanism of the fore and hinder extremities presents some differences. 1 hat of the fore 

 limb may be said to exhibit altogether a different character. The fore-leg bones are much less angular, 

 and appear framed purposely to receive the weight imposed on them by the impulse ot the hinder limbs. 

 This weight thev are destined to sustain, until the elevation is forced on them by the tendency the general 

 inclined mass has to meet the ground, or to find its common centre in the earth. The tore extremities, 

 under this view of the matter, could not have been placed with equal wisdom in any other situation, nor 

 have taken any other form. The hinder extremities having less weight on them, and at no time bearing an 

 increase of pressure, as the fore do by the impetus communicated from behind, are much more angular; 

 and their angles, by being thrown into a backward direction, afford the necessary impetus for the projection 

 of" the body forward. This important operation of impelling the mass being almost wholly dependent on 

 the hind extremities, as that of sustaining it is principally confined to the fore extremities ; so the former 

 are also much stronger in point of muscular apparatus; by which their angles can be advantageously 

 opened and closed with superior effect in progression. 



Sect. IV. Anatomy and Physiology of the soft Parts. 



6333. We shall include under appendages to bone, the muscles and tendons, blood- 

 vessels, absorbents, nerves and glands, integuments, head, ear, eve, nose, mouth, neck, 

 chest, abdomen, organs of gent-ration, and the foot. 



Subsect. 1. Appendages to Bone, the Muscles, and Tendons. 



fV534. The appendages to bone are cartilages or gristle, periosteum, medulla or marrow, ligaments, and 

 synovia or joint oil. 



