DIGESTION 209 



charge of nerve impulses through the hypogastric nerve to the internal 

 sphincter and perhaps the external sphincter as well, calling forth their 

 relaxation or inhibition. With the discharge of the feces the former condi- 

 tion is re-established. A stimulus, the nature of which is not fully known, 

 causes a stimulation of the inhibitor center for the rectal muscles and a 

 stimulation of the motor center for the sphincters, the nerve impulses reaching 

 the muscles through the hypogastric and pelvic nerves respectively. 



