9S PRACTICE OF AGRICULTURE. Part III. 



strength, and in the different lengths and directions of the parts, but also, in some degree, 

 in their uses. 



5655. The femur or thigh hone {3, 4:) is the ]argest o{ the body, its vast indentations and risings, almost 

 peculiar to it, shew the great strength of the muscles inserted into it. It articulates with the acetabulum 

 ^r hip joint by a strong head called the iu//rWwc. In this situation it is held not only by a powerful 

 capsular ligament, and still more powerful muscles, but by an admirable contrivance resulting from a liga- 

 mentous rope, which springs immediately from the middle of its head, and is firmly fixed within the 

 socket of the joint. In its natural situation it is not perpendicular as the human femur, but inclines to 

 an angle of about 45. This bone presents large protuberances for the attachment of very powerful 

 muscles called trochanters. Throughout it exhibits a mechanism uniting the combined qualities of 

 celerity and strength unknown to other animals. The inferior end of this bone is received by its condyles 

 into depressions of the tibia, while the patella or knee-pan slides over the anterior portions of both 

 bones. 



5656. The patella (5), which is by farriers called the stifle, is nearly angular, and serves for the insertion 

 of some of the strongest muscles of the thigh, which are then continued down to the leg. It thus 

 appears to act as a pulley. 



5657. The tibia or leg bone (6, 6) is usually in horsemen's language called the thigh. It is a bone formed 

 of a large epiphysis, with a small attached part called the fibula (7), a long body, and-an irregular inferior 

 ,end, adapted to the peculiarities in shape of the principal bones of the back with which it articulates. 

 The obliquity in the situation of this bone corresponds with that of the femur, being as oblique back- 

 wards as the former is forwards. The length of the tibia is a prominent character in all animals of quick 



progression ; and in this respect it corresponds with the fore arm, and the remarks before made on that, 

 apply with even more force to this that length is advantageous to the celerity, but less so to the ease 

 of the motion. 



5658. The fibula (7, 7) forms a prominent instance, in common with the splint bones, of what was re- 

 marked in the outset of our osteological detail of the extremities that many parts whose uses were not 

 apparent, would be found to be organs of harmony, placed in the body to prevent the interruption to the 

 completing the general plan of animal organization. In this way the fibula appears but a process spring, 

 angfrom the posterior part of the tibia, forming but the rudiments of the human bone of that name. 

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

 contrary, perfect. 



5659. The tarsus, or hock of the horse (10, 10), is a striking instance of the perfect mechanism displayed 

 in the bony structure of this admired animal. It is formed by an assemblage of six bones, and sometimes 

 of seven; while in the ox, sheep, and deer, there are seldom more than five. Between these bones there 

 is little motion, yet there is sufficient to give a spring to the parts, and to preserve the joints from the 

 veflfects of shocks, &c. As the human anatomy is generally received as the standard of comparison, we must, 

 in order to a proper consideration of the hock, consider it as the instep and heel ; and all the parts beyond 

 it as the foot. The human tarsus, and that of some quadrupeds, as the monkey, and some varieties of the 

 bear, makes a right angle with the tibia in standing or walking ; but in the horse, the hock makes an 

 open angle with the tibia, and is far removed from the ground. In him and the greater number of 

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

 pillar of the limb. In the horse, therefore, the point of the hock is the true point of the heel, and, as in the 

 iiuman figure, the great twisted tendons of the gastrocnemii muscles are inserted into it : but the appella- 

 tion of tendo achilles, would be too forced here. A broad hock, as already observed in the exterior con- 

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

 the calcaneum or heel bone of the hock, the longer must be the lever that the muscles of the thigh act 

 by ; and a very slight increase or diminution in its length must make a very great difference in the 

 power of the joint. It is by this tendon acting on this mechanism, that when the animal has inclined 

 the angle between the canon and the tibia, or in other words, when the extremities are bent under him 

 in the gallop or trot, that he is enabled to open it again. The bones of the hock, like those of the knee, 

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

 (Calcaneum and cuboid bones, that thfe disease called curb is to be attributed ; and to a similar inflam- 

 matory affection of the ligaments in the front of the hocks, that .Vyoaws 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 essentially from the corresponding bones in the fore extremities as to need an 

 individual description. It may, however, be remarked, that the hinder canon or shank bone is longer 

 than the fore, 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. 



Sect. IV. 0/ the Physiology or Functions of the Horse. 



5660. The admirable mechanism displayed in the composition of the body of the horse, 

 will appear by considering its various functions generally and particularly as a whole. 



SuBSECT. 1. General Functions of the Bony Skeleton. 



5661. The skeleton of the horse will be found to present nearly a quadrilateral figure, 

 having an inclined cylinder resting on four supporting 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 fore legs; by which the propelling force of the hinder 

 extremities is relieved by the maximum of strength thus transferred. The 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 the cylinder may be such as not to support its own 

 weight; nature, therefore, has limited the length of the spines of animals: hence, cete- 

 rihus paribus, a long-backed horse must be weaker than a short one ; and thus, likewise, 

 small horses can carry proportionably more than larger ones. The four pillars which 

 support this cylinder, are not perpendicular partially ; but they are so totally : for a 

 perpendicular drawn from their common centre of gravity, will be found to fall nearly 

 in their common base, by which means they are supported as firmly as though their in- 

 dividual axes had been in a line perpendicular to the horizon. Had they been perpen- 

 dicularly opposed to each other, there could have been but little elasticity, and conse- 

 quent ease in motion : every exertion would have proved a jar, and every increased 

 effort would have produced laxation or fracture. To increase our admiration of this 



