412 Mr. F. O.Ward's Physiological Remarks 



the effect of equalizing the length of the muscular fibres. 

 But independently of the consideration that the insertion would 

 have been quite as compact if the tendon had been thick and 

 single, instead of thin and double; and that the fibres are not 

 by any means equal in length, according to the second hy- 

 pothesis, — bolh explanations are defective, in as much as they 

 show no reason for the muscular fibres crossing each other, 

 so that the upper are attached below, and the lower above, the 

 medium point of the whole insertion. 



I think that the arrangement becomes perfectly intelligible 

 Avhen the separate actions of the upper and lower portions of 

 the muscle are considered with reference to the species of mo- 

 tion those actions require. 



The separate action of the lower fibres is to depress the 

 arm when raised; that of the upper fibres, to raise the arm 

 when depressed. Of this any person may convince himself 

 by laying the hand on the muscle ; first, while imitating the 

 action of hammering; and then, while raising or supporting 

 a weight: in the former case he will perceive a momentary 

 convulsive contraction of the lower fibres; and, in the latter, 

 a steady, continued tension of the upper. 



In the third and fourth sketches which exhibit these posi- 

 tions, the several directions of the humerus, and of the upper 

 and lower portions of the muscle, are represented by lines, the 

 arrow-head denoting in each figure which set is exerted, and 

 in what direction it acts. 



Now since the humerus is a lever having the fulcrum at 

 one end and the resistance at the other, the velocity it ac- 

 quires must be directly, and the force inversely, proportionate 

 to the proximit}' of the moving power to the fulcrum. 



The most common, and therefore most important purpose, 

 to which the depressing fibres are applied, is that of bringing 

 down the arm in using the hammer, pickaxe, &c., as the car- 

 penter, blacksmith, goldbeater, and a hundred other artizans 

 testify. In these motions velocity alone is required from the 

 muscle, the gravity of the tool giving force to the blow; and 

 to produce this velocity the lower division is attached near to 

 the fulcrum. Again, the commonest employment of the upper 

 fibres consists in such actions as lifting, drawing, and the like, 

 in which force, not velocity, is the desideratum ; and, in order 

 to obtain force at the expense of velocity, the insertion of 

 these fibres is brought down as far as possible towards the re- 

 sistance. 



It is remarkable that, in each instance, that very fasciculus 

 of the muscle, which possesses most of the action peculiar to 

 its division, possesses likewise that very point of the insertion 



