42 SENSORIAL ACTIONS. Sect. XI. 3. 2. 



have thus gradually been brought to act 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 inftinet. 



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

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

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

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

 fuppofed to be aflbciated 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 tlie 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 ac~r. from the irritation of diftention, 

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

 men and diaphragm are brought into motion by aflbciation with 

 thofe cf the fphin&er and rectum. 



SECT. 



