OF THE MUSCLES. 83 



Or let a person only observe his own hand whilst he is 

 writing; the number of muscles, which are brought to 

 bear upon the pen ; how the joint and adjusted operation 

 of several tendons is concerned in every stroke, yet that 

 five hundred such strokes, are drawn in a minute. Not a 

 letter can be turned without more than one or two or three 

 tendinous contractions, definite, both as to the choice of 

 the tendon and as to the space through which the con- 

 traction moves, yet how currently does the work proceed ' 

 and when we look at it, how faithful have the muscles 

 been to their duty, how true to the order which endeavour 

 or habit hath inculcated ! For let it be remembered, that, 

 whilst a man's hand writing 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 the do- 

 cility. 



IL Regarding the particular configuration of muscles, 

 spliincter or circular muscles appear to me admirable pieces 

 of mechanism. (PL XIV. fig. 3.) It is the muscular pow- 

 er 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 mechanical, is not the only thing in sphincters 

 which deserves our notice. The regulated degree of con- 

 tractile force with which they are endowed, sufficient for 

 retention, yet vincible when requisite ; together with their 

 ordinary state of actual contraction, by means of which 

 their dependence upon the will is not constant but occasion- 

 al, gives to them a constitution of which the conveniency 

 is inestimable. This their semi-voluntary character, is ex- 

 actly such as suits with the wants and functions of the ani- 

 mal, 



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 

 diagonal motion is produced, by the contraction of tendons, 

 pulling in the direction of the sides of the parallelogram. 

 This is the case, as hath been already noticed, with some 

 of the oblique nutations of the head. Sometimes the num- 

 ber of co-operating muscles is very great. Dr. Nieuentyt, 

 in the Leipzic Transactions, reckons up a hundred muscles 

 that are employed every time we breathe ; yet we take in, 

 or let out, our breath, without reflecting what a work is 

 thereby performed ; what an apparatus is laid in of instru- 



