[ r 79 ] 
2d, Irritability, and 
3d, Nervous force. 
< , 1 • / \ . 
Of Contractility. 
Mufcles poflefs contradlility in com¬ 
mon with every other part of the body, 
if we except the bones. Thus they yield 
to a certain point, to an extending power, 
and return upon themfelves fo as to referve 
their original fize as foon as the extend¬ 
ing force is withdrawn. 
But when the parts have taken on their 
original flate, this power does not remain 
inactive, but operates continually by ma¬ 
king a gentle uninterrupted effort to bring 
the elements of the fibres into ftill more 
intimate contadt. 
% 
Thus, if we divide a mufcle in its 
length, whether in the living or dead fub- 
jedt, the divided parts recede from each 
other fo as to leave a considerable fpace 
between them. 
N 2 
If 
