4-74- MUSCLES. 



perfect composition of the part during life than after death. A 

 muscle, however, may act, without shortening or growing thicker. 

 If we hold, or act upon, a resisting body without moving it, the 

 muscle, though in action, does not shorten. Again, a muscle 

 may be made to shorten without contraction. We can bend 

 the extremities of a person asleep, and thus his flexors be pas- 

 sively shortened. 



" To attempt, with J.and D. Bernouilli and other mathematical 

 physicians, to reduce the shortening of muscles to a general 

 admeasurement, is rendered impossible, by the great difference, 

 among other causes, between the hollow and solid muscles in 

 this respect, and between the solid muscles themselves, v. c. 

 between straight muscles (such as the intercostals) and sphinc- 

 ters." 



Some have peculiar actions, dependent upon figure, situation, 

 &c., " and, consequently, varying so much as to be referable to no 

 general laws. 



" To cite one instance out of many, that action of certain 

 muscles is peculiar and anomalous which seldom occurs alone, 

 but nearly always subsequently to, or simultaneously with, the 

 action of some of a different order. Such is that of the lum- 

 bricales, when, during rapid motions of the fingers, they follow 

 the action of other muscles of the metacarpus and fore-arm; and 

 of the lateral recti muscles of the eyes, the adducens of either 

 of which seldom acts unless simultaneously with the abducens of 

 the other eye. 



"And, on the other hand, although the action of the flexors is 

 generally so much stronger than that of their antagonists the 

 extensors, that, when the body is at rest, the arms, fingers, &c. 

 are a little bent, this docs not so much depend upon the strength 

 of the contraction of the flexors, as upon the voluntary relaxation 

 of the extensors for our own relief. 



"Every muscle has, moreover, a peculiar mechanism 1 , adapted 

 to the individual motions for which it is intended. 



" Besides the determinate figure of each, many other kinds of 

 assistance are afforded to their peculiar motions, v. c. by the 

 biirsce mucos<z, chiefly found among the muscles of the extremities ; 

 the annular ligaments by which some are surrounded ; the fat in 



1 " P. J. Barthez, Nouvelle Mechanique des Mouvemens de VHomme et des 

 Animaux. Carcass. 1798. 4to." 



