THE MUSCLES. \>7 



for let it be remembered, that while a man's handwriting 

 is the same, an exactitude of order is preserved, whether he 

 write well or ill. These two instances of music and writing 

 show not only the quickness and precision of muscular action, 

 but thj docility.^ 



II. Regarding the particular configuration of muscles, 

 ^pJiincter or circular muscles appear to be admirable pieces 

 of mechanism. t It is the muscular power most happily 

 applied — the same quality of the muscular substance, but 

 under a new modification. The circular disposition of the 

 fibres is strictly mechanical ; but, though the most mechan- 

 ical, is not the only thing in sphincters which deserves our 

 notice. The regulated degree of contractile force with which 

 they are endowed, sufficient for retention, yet vincible when 

 requisite, together with their ordinary state of actual con- 

 traction, by means of which their dependence upon the will 

 is not constant but oc.casional, gives to them a constitution 

 of which the conveniency is inestimable. This their semi- 

 voluntary character is exactly such as suits with the wants 

 and functions of the animal. 



III. We may also, upon the subject of muscles, observe, 

 that many of our most important actions are achieved by 

 the combined help of different muscles. Frequently a diag- 

 onal motion is produced by the contraction of tendons pulling 

 in the direction of the sides of the parallelogram. This is 

 the case, as has been already noticed, with some of the 

 oblique nutations of the head. Sometimes the number of 

 cooperating muscles is very great. Dr. Nieuentyt, in the 

 Leipsic Transactions, reckons up a hundred muscles that are 

 employed every time we breathe ; yet we take in or let out 



* Fig. 5 exhibits the principal muscles ol the palm of the hand : 

 fl, a, a, a, are small muscles indispensably necessary in rapid move- 

 ments of the fingers ; c, c/, c, are muscles of the thumb ; f, g-, of tha 

 little finger. 



t Fig. 6 exliibits examples oi sphincter muscles : a, that encircling 

 the eyelid, closing and compressing the eye ; 6, is the muscle surround- 

 ing the mouth, and contracting the lips. 



Nat. Theol. 5 



