MUSCLE. 35 1 



The immediate cause of cadaveric rigidity has never yet 

 been satisfactorily explained. Some have supposed that it de- 

 pends upon the coagulation of the blood in the capillaries an 

 hypothesis scarcely tenable : others, with more reason, con- 

 ceive that it proceeds from the solidification of the fibrin of 

 which muscle is chiefly constituted that it is in fact a phe- 

 nomenon precisely analogous to the coagulation of the fibrin 

 of the blood. 



An explanation differing from both of the former has sug- 

 gested itself to my mind. I conceive that muscular con- 

 traction may possibly be brought about by the stimulus of 

 the thinner and more watery parts of the blood, &c. acting 

 on the still irritable muscular fibre, and which are known to 

 escape from their containing vessels very shortly after the 

 extinction of life. Of this passage of fluid through the walls 

 of its receptacle we have a familiar instance in the case of 

 the gall-bladder and its contents. 



Two other points require to be briefly alluded to in rela- 

 tion to the subject of muscular contraction : the first is the 

 muscular sound heard on applying the ear to a muscle in 

 action, and which has been likened by Dr. Wollaston * to 

 the distant rumbling of carriage wheels : the second relates 

 to the fact made known by MM. Bequerel and Breschet, 

 that a muscle during contraction experiences an augmentation 

 of temperature. 



DEVELOPMENT OF MUSCLE. 



The muscular tissue, like the majority of those which 

 have hitherto been described, takes its origin in cells. 



The term fibre is applicable only to the striped form of 

 muscle in which a number of fibrilla3 are included in an in- 

 vesting sheath common to them : these striped fibrilta of the 

 striped fibre of voluntary muscles, are analogous to the un- 

 striped fibrillas of the involuntary muscles. 



The process of the development of muscle may be divided 

 into three stages : 



* Phil. Trans. 1811. 



