Book VII. ANATOMY OF THE HORSE. 895 



lost. The 'iliu7n is the most considerable, and forms the haunches by a large unequal protuberance 

 which, when very prominent, occasions the horse to be called ragged hipped. The next largest portion 

 is ihQischiiim or hip bone, on each side. It forms a part of the cotyloid cavity, or hollow for the thi^h 

 bone, and then stretches back also into a tuberosity which forms the jwints of the buttocks. The pubis 

 or share bone is the least of the three : in conjunction with the former it forms the acetabulum or cavity 

 in which the head of the thifrh-bone lodges. The pelvis or basin is attached to the sacrum by ligaments 

 of immense strength ; but it has no bony union, by which means, as in the tore extremities, some play 

 is given, and the jar of pure bony connection is avoided. The ossa coccygis, or bones of the tail, vary 

 from eight to sixteen, but are very commonly thirteen or fourteen. 



5G43. The thorax or chest comprises the sternum or breast bone, and the ribs. The sfernufn (w) of 

 the horse is inclined like the keel of a ship to which the ribs are attached by strong ties. The ribs {x x) 

 are usually eighteen to each side, of which eight articulate with the sternurn, and are called true, while 

 the remaining ten, uniting together by intervening cartilages, are called false ribs. The centrals are 

 the longest, those more anteriorly as well as posteriorly are less so: the first is placed peri)endicularly, 

 the second less so, and their obliquity as well as dimensions increase as they advance, so as to enlarge 

 the chest to an almost circular form, which is the most desirable ; but when they are less arched, the 

 belly partakes of the defect, and a flat-sided horse is always without much carcase also. 



SuBSECT. 3. T/ie Anatomy of the Extremities. 



5644. An examination of the bony parts of the limbs excites our admiration at the 

 wonderful mechanism displayed in their formation : but this is not all, they must be 

 regarded as presenting parts which appear less useful than intended to keep up that vast 

 chain of continuity and similarity observable throughout nature's works. In the follow- 

 ing explanation we shall have occasion to notice several of these. 



5645. The scapula or shoulder blade presents itself first {k, I), and is a broad and rather triangular bone 

 very unlike the same bone of the human figure, having neither acromion, coracoid, nor recurrent process : 

 neither is its situation at all similar to the human blade bone applied to the back ; for in this instance the 

 horse may be said to have no proper back, but to be made up of sides and chest. In man, the scapula 

 is in a direct angle with the humerus, but in the horse it does not pass out of the plane of the arm. Its 

 up3rior surface is furnished with a considerable cartilage {l,m), by means of which its surface is aug- 

 mented without weight. The posterior surface ends in a superficial cavity called glenoid, which receives 

 the head of the humerus or arm bone. It is divided in its upper surface by its spine. The shoulder blade, 

 as has been already shown in the exterior conformation, has neither bony nor ligamentous union, but is 

 iield in its situation by very powerful muscles, as the serratus major, j)ectorals, and others. Its usual 

 situation is to a plane perppndicular to the horizon, at an angle of thirty degrees ; and it has a motion in 

 its greatest extent of twenty degrees: hence, as it does not pass beyond the perpendicular backwards, 

 so the more oblique its natural situation, the more extensive are its motions. 



5545. The humerus or arm bone (m), is so concealed by muscles as to be overlooked by a cursory ob- 

 server, and hence the radius or next bone is popularly called the arm. It extends from what is called 

 the point of the shoulder, but which in fact is a protuberance of its own to the elbow, forming an angle 

 with the scapula, and extending obliquely backwards as that does forwards. Near its upper extremity it 

 sends off a very powerful head to articulate with the shoulder blade. The motions of the humerus are 

 necessarily confined to a removal from its inclined,point backward to the perpendicular line of the body. 

 When this bone is too long, it carries the fore legs too much under the animal, and if this defect be 

 joined to a shallow upright shoulder, the evil will be increased. It however fortunately happens that 

 oth the angle and extent of these two parts are usually regulated by each other. 



5647. The fore arm {n n, o o) is composed of the radius (oo), and an appendage united to it, which in 

 man and some animals, forms the ulna (n n), but which as the leg of the horse requires no ro-. 

 totary motion was unnecessary in him. Here, however, to keep the link of resemblance in all her 

 children of the higher order, nature has stretched out a large process ; which in the colt is really distinct, 

 and may then deserve the name of ulna ; and in the adult horse unites with the radius, and serves as 

 an attachment to muscles. On the .slightest inspection of the skeleton, it will appear how much the 

 motions of the fore leg must depend on the length and obliquity of this process ; which acting on the princi. 

 pie of a lever in the extension of the arm, must necessarily, as it is either long or short, make all the 

 difference between a long and a short purchase. The breadth of the arm as it is called, at this part, will 

 from this reasoning be seen be very important. This bone articulates with the knee by its inferior 

 portion. 



5648. The carpus or wrist, called the knee (pp), is composed of seven bones, whose principal uses appear 

 to be to extend the surface of attachment of ligaments and tendons, and by their interruptions to lessen 

 the shocks of progression. It may be remarked that all hoofed quadrupeds have the anterior extremi- 

 ties permanently in the state of pronation, or with what is called the back of the wrist turned outwards. 

 The carpal bones articulate with each other, and have one investing capsular ligament, by which means 

 the smallest wound of the knee which penetrates this ligament, has the effect of opening the whole joint : 

 hence the quantity of synovia or joint oil which escapes in these cases, and hence also the dangerous con- 

 sequences which ensue. 



5649. The metacarpus {q q,rr), canon or shank, is formed of one large metacarpal bone (q), and two 

 small ones (r). Here the wide palm of the human, and the paw of the digitated animal, is formed into 

 one solid cylindrical bone, and two small additamentorffi, called splint bones ; which are united with it by 

 strong ligamentary attachment, converted by age into a bony one. Although these additions may some- 

 what increase the surface of attachment, their principal use appears to be to keep up the connection with 

 thedigitii, of which they apjiear the rudiments. In thecow there are no splintbones, but the uniformity is 

 more perfectly kept up by the divided hoof: in her, therefore, the canon branches at its inferior surface 

 into condyles for the reception of the two claws. 



5650. The pastern ijt t). The rest of the extremity below the canon, consists of one phalange only, 

 comprising all the mechanism, and a double i)ortion of comi)lexity of all the phalanges of the digitated 

 tribes. P'our bones enter into its composition with two small sesainoids {s s) to each fetlock ; placed 

 there not only to act as a spring and prevent concussion, but to throw the tendon of the foot which runs 

 over them, farther from the centre of motion. The pastern bone is situated obliquely forward^ and on 

 which obliquity depends the ease and elasticity of the motion of the animal : nevertheless when it is too 

 long, it requires too great efforts in the tendons and ligaments to preserve it in its situation j and thus 

 long jointed horses must be more subject to fatigue and to strains than others. 



5651. Thelesser pastern or coronari/ bone {f,v) receives the great pastern, and below expands into a 

 considerable surface articulating with the coltin and navicular bones. 



5652. The coffin bone {v v) forms the third phalange, and corresponds in shape with the hoof It is 

 very porous, and laterally receives two i r minent cartilages. It is around the outer surface of this bone 

 that the sensible lamina are attached ; and the inferior surface receives the flexor tendon. 



5653. The navicular nut or shuttle bone is situated at the posterior part of the coffin, and unites with 

 that and the preceding bone. 



5654. The posterior extremities differ muchfroin the anterior, not only in their superior 



