MISCELLANEOUS ESSAYS. 



881 



by two muscles drawing against, 

 and balancine; each other. Inahe- 

 jniplegia, when the muscle on one 

 side is weakened, the muscle on the 

 other side draws the mouth awry. 



3. Another property of the mus- 

 cles, which could only be the result 

 of care, is their being almost uni- 

 versally so disposed as not to ob- 

 stru(5t or interfere Avith one ano- 

 ther's a6tion. I know but one in- 

 stance in which this impediment is 

 perceived : we cannot easily swallow 

 whilst we gape. This, I understand, 

 is owing to the muscles employed in 

 the adl of deglutition, being so im- 

 plicated with the muscles of the 

 lower jaw, that, whilst these last 

 are contrafted, the former cannot 

 aft with freedom. The obstruftion 

 is, in this instance, attended with 

 little inconveniency ; but it shews 

 "what the effe6t is where it docs exist, 

 and what loss of faculty there would 

 be, if it were more frequent. Now 

 "when we refleft upon the number of 

 muscles, not fewer than four hun- 

 dred and forty-six in the human 

 body, known and named,* how 

 contiguous they lie to each other, in 

 layers, as it were, over one another, 

 crossing one another, sometimes 

 embedded in one another, sometimes 

 perforating one another, an arrange- 

 ment, which leaves to each its li- 

 berty and its full play, must neces- 

 sarily require meditation and coun- 

 sel. 



4. The following is oftentimes 

 the case with the muscles. Their 

 action is wanted where their situa- 

 tion would be inconvenient. In 

 which case the body of the muscle 

 is placed in some commodious posi- 

 tion at a distance, and made to 

 communicate with ths point of ac- 



tion, by slender strings or wires. If 

 the muscles, which move the fingers, 

 had been placed in the palm or back 

 of the hand, they would have swel- 

 led that part to an awkward and 

 clumsy thickness. The beauty, the 

 proportions of the part, would have 

 Jieen destroyed. They are there- 

 fore disposed in the arm, and even 

 up to the elbow ; and aft by long 

 tendons, strapped down at the 

 wrist, and passing under the liga- 

 ment to the fingers, and to the joints 

 of the fingers, which they are seve- 

 rally to move. In like manner, the 

 muscle^ which move the toes, and 

 many of the joints of the foot, how 

 gracefully are they disposed in the 

 calf of the leg instead of forming an 

 unwieldy tumefaftion in the foot it- 

 self? The observation may be re- 

 peated of the muscle which draws 

 the niftitating membrane over the 

 eye. Its ofBce is in the front of the 

 eye, but its body is lodged in the 

 back part of the globe, where it is 

 safe, and where it incumbers no. 

 thing. 



.5. The great mechanical variety 

 in the figure of the muscles may be 

 thus stated. It appears to be a 

 fixed law, that the contraftion of a 

 muscle shall be towards its centre. 

 Therefore the subjeft for mechanism 

 on each occasion is, so to modify 

 the figure, and adjust the position 

 of the muscle, as to produce the 

 motion required, agreeable with this 

 law. This can only be done by 

 giving to different muscles a diver- 

 sity of configuration, suited to their 

 several offices, and to their situatioa 

 wilh rcspeft to the work which they 

 have to perform. On which ac- 

 count we find them under a multi- 

 plicity of forms aud attitudes j som6- 



VoL. XLVI. 



* Kcill's Anat. p. «95, cd. :id. 



times 



