3 4 3 Mnfdes of involuntary Motion. [Book IX. 



fuch as chemical or mechanical injury, and flill more 

 remarkably by the electric fhock, which influences 

 mufcks infenfible to every other kr^own ftimulus.. 



Mufcles retain a contractile power for a confider- 

 able time after they are removed from the living 

 body ; this power, however, gradually diminifhes, till, 

 fboner or later, according to a variety of circum- 

 ftances, it ceafes altogether. The mufcles of invo- 

 luntary motion, when removed fnem the reft of the 

 body, retain their contractile power longer than thofe 

 of voluntary motion j the former, indeed, from this 

 circamftance, as well as from their uninterrupted mo- 

 tion in the living body, feem to be pofTerled of a 

 capacity for contraction beyond that of the other 

 mufcles. 



What has been hitherto flated, relates principally 

 to the more remarkable mufcular contractions, by 

 which the actions of the body are performed , but it 

 is to be remembered, that befides thefe occafional 

 contractions, there is a continual tendency in the 

 mufcular fibre to fnorten itfelf , and even after death* 

 when a mufcle is divided, the wounded extremities 

 recede from each other. A ftrong illuftraticn of this 

 circumftance is obtained, by obferving the confe- 

 quence of dividing a mufcle in the living body, for in 

 this cafe its antagonift will conftantly draw the parr 

 which thefe mufcles were defigned to move, towards 

 its own fide. 



That power by which the different parts of a mufcle, 

 divided after death, recede from each other, is called 

 the vis mortua, and is common to mufcles and other 

 animal fibres. The power by which a mufcle obeys a 

 ftimulus after being feparated from the body, or after 

 its communication with the fenlbrium has been cut 

 off by other meansa as by dividing or tying its nerves, 



