194 OF MUSCULAR MOTION. 



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 

 sphincters. 



313. The peculiar actions of muscles (311) corres- 

 pond with their peculiar powers, and consequently vary 

 so much as to be referrible to no general laws. 



To cite one instance out of many, that action of cer- 

 tain muscles is peculiar and anomalous which sel- 

 dom occurs alone but nearly always subsequently to, 

 or simultaneously with, the action of some of a dif- 

 ferent order. Such is that of the lumbricales, 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, either 

 adducens of which seldom acts, unless simultaneously 

 with the abducens of the other eye. 



The commonly received law — that a muscle during 

 its contraction draws the more moveable point of 

 insertion to the more fixed, must be considered, as 

 Winslow wisely remarks,* perfectly relative and sub- 

 ject to various limitations. Thus, for example, some- 

 times the one point, and sometimes the other, may be 

 the more moveable; accordingly as the united action 

 of. many different muscles may render the opposite 

 more fixed. 



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 does 



* Mem. dc Mead, des Scienc. de Parii. 1720. 



