42 SENSORIAL ACTIONS. SECT. XL 3. 2* 



have thus gradually been brought to aft in concert, which hab- 

 its began to be acquired as early as the very formation of the 

 moving organs, long before the nativity of the animal ; as ex- 

 plained in the Section XVI. 2. on inftinct. 



2. There are many motions of the body, belonging to the ir- 

 ritative clafs, which might by a hafty obferver be miftaken for 

 aflbciated ones ; as the periftaltic motion of the ftomach and in- 

 teftines, and the contractions of the heart and arteries, might be 

 fuppofed to be affbciated with the irritative motions of their 

 nerves of fenfe, rather than to be excited by the irritation of 

 their mufcular fibres by the diftention, acrimony, or momentum 

 of the blood. So the diftention or elongation of mufcles by ob- 

 jects external to them irritates them into contraction, though 

 the cuticle or other parts may intervene between the ftimulating 

 body and the contracting mufcle. Thus a horfe voids his ex- 

 crement when its weight or bulk irritates the rectum or fphinc- 

 ter ani. Thefe mufcles act from the irritation of diftention, 

 when he excludes his excrement, but the mufcles of the abdo- 

 men and diaphragm are brought into motion by affociation with 

 thofe of the fphinder and rectum. 



SECT. 



