[ 879 ] 



MISCELLANEOUS ESSAYS. 



Of the Muscles, icith their Tendons, 

 being the Indruinents by nhich 

 Animal Mofioti is performed. — ■ 

 Frojn Palejj's Natural Theolugj/. 



It will be our business to point 

 out instances in wiiich, and proper- 

 ties with respeft to which, the dis- 

 position of these muscles is as stri6t- 

 \y mechanical, as that of the wires 

 and strings of a puppet. 



1. We may observe, what I be- 

 lieve is universal, an i'xa&. relation 

 between the joint, and the mnscles 

 which move it. Whatever motion 

 the joint, by its mechanical con- 

 struction, is capable of performing, 

 that motion, the annexed muscles, by 

 their position, are capable of pro- 

 ducing. For example: if there be, 

 ■ as at the knee and elbow, a hinge 

 joint capable of motion only in the 

 same plane, the leaders, as they are 

 called, i. c. the muscular tendons, 

 are placed in dire(5tions paralTel to 

 the bone, so as by the contraction or 

 relaxation of the muscles to which 

 they belong, to produce that motion 

 and no other. If these joints were 

 capable of a freer motion, there arc 

 no mus.c]esto produce it. Whereas, 

 at the shoulders and hip, where the 

 ball and socket-joint allows, by its 

 •onstruction, of a rotary or sweeping 

 motion, tendons are placed in such a 

 position, and pull ia such a direc. 



tion, as to produce the motion of 

 which the joint admits. For in- 

 stance, the sariorius, or taylor's 

 muscle, rising from the spine, run- 

 ning diagonally across the thigh, and 

 taking hold of the main bone of the 

 leg a little below the knee, enables 

 us, by its contraction, to throw one 

 leg and thigh over the other ; giv- 

 ing effect, at the same time, to the 

 ball and socket-joint at the hip, and 

 the hinge joint at the knee. Ther& 

 is, as we have seen, a specific mecha- 

 nism in the bones for the rotatory 

 motions of the head and hands ; 

 there is also, in the oblique direc- 

 tion of the muscles belonging to 

 them, a specific provision for the 

 putting of this mechanism of the 

 bones into action. And mark the 

 consent of uses. The oblique mus- 

 cles would have been inefficient 

 without the articulation : the articu- 

 lation would have been lost, without 

 the oblique muscles. It may be 

 proper, however, to observe with 

 respcft to the head, although I 

 think it does not vary the case, that 

 its oblique motions and inclinations 

 are often motions in a diagonal, 

 produced by the joint action of 

 muscles lying in straight directions. 

 But whether the pull be single or 

 combined, the articulation is always 

 such, as to be capable of obeying 

 the aCtion of the muscles. The ob- 



li%u« 



