THE ARM. 365 



When describing tlie proper obliquity of tlie shoulder, it was stated that 

 the power was exerted with most advantage in a line perpendicular to thu 

 arm of the lever, and that the slightest deviation from that hne was mani- 

 festly disadvantageous. If the reader Avill examine the cut, he will perceive 

 that muscles from the shoulder and the bone of the arm. take a du-ection 

 much nearer to a perpendicular line in the long than in the short elbow, 

 and therefore act with proportionably greater advantage ; and if this 

 advantage from the dii-ection in which the power is appKed to that which 

 we gain from the increased length of the bone is considered, it will be 

 plain that the addition of one-third to the length or projection of the 

 elbow would be attended by a saving of one-half in the expenditure of 

 muscular power. There is, however, a limit to this. In proportion as 

 the elbow is lengthened, it must move over a greater space in order to give 

 the requisite extension to the limb ; and consequently the muscles which 

 act upon it must be lengthened, otherwise, although the action might be 

 easy, it would be confined. There must be harmony of iJroportion in the 

 diSerent parts of the hmb, but a deep elbow, within a certain rano-e, is 

 always connected with increased power of action. 



Enlargements sometimes appear about the elbow, either the consequenco 

 of a violent blow, or from the calkins of the shoes injuring this part when 

 the horse sleeps with his legs doubled under him. If a seton is passed 

 through the tumour, it will sometimes rapidly diminish, and even disap- 

 pear ; but if it is of considerable magnitude, the skin should Le opened 

 along the middle of the swelling, and the tumoui' dissected out. The 

 result of these operations may be successful, but if the operator does not 

 repent of having performed them long before they heal again, he is a very 

 fortunate fellow. The better part of valour, however, is discretion, and in 

 the cases alluded to, supposing, as is generally the case, that no bad effect 

 beyond the eyesore accompanies it, it had better, much better, be left alone. 



One of the most powerful muscles for bending the leg, the jlexor Lmcliii, 

 arises from the point of the shoulder, in the form of a large round tendon, 

 which rans over a groove or pulley in the front of the humerus : it then 

 swells out into a round fleshy body, contributing materially to the bulk in 

 front of the arm, and is inserted into a tubercle in the inner and uj)per 

 part of the radius. It is the main muscle by which, almost alone, the 

 whole of the leg below the arm is bent. It acts at great disadvantage. It 

 is inserted into the very head of the bone of the arm, and expanded even 

 upon the joint. Then the power is applied almost close to the centre ot 

 motion, while the weight to be raised is far distant from it. The power 

 is thirty times nearer the centre of motion than is the weight, and calcu- 

 lating as before, the weight of the arm and rest of the hmb at 60 lbs., it 

 must act >vith a force of thirty times sixty, or 1,800 lbs. In addition to 

 this, the line of the dii^ection of the force strangely deviates from a per- 

 pendicular : the direction of the muscle is nearly the same as that of the 

 limb, and the mechanical disadvantage is almost incalculably great. We 

 will take it as only ten times more : then this muscle, and its feeble 

 coadjutors, act -with a force of ten times 1,800 or 18,000 lbs. Wliy this 

 almost incredible expenditure of muscular power ? First, that the beauty 

 of the limb might be preserved, and the joint might be compact. If the 

 tendon had been inserted half way do\\ai the arm, the elbow-joint would 

 have offered a very unsightly appearance. 



Beauty of form, however, is but the least result of this conformation. 

 Extensive and rapid motion are among the excellences of the horse. He is 

 valuable in proportion as he has them combined with stoutness ; and by 

 tliis conformation of the limb could he alone obtain them. Therefore the 

 tendon is at first unusually strong: it plays through the natural but 



