1.   The occurrence and duration of external anal sphincter activity during rectal distension.

2.   In contrast, none of the spinal patients produced an increase in anal pressure or an increase in external anal sphincter activity when asked to contract their sphincter.

3.   Rectal contractions were associated with prolonged increases in external anal sphincter activity and anal pressure in all normal subjects.

4.   The external anal sphincter responses to intermittent rectal distension were noticeably attenuated in spinal patients compared with normal subjects.

5.   The absence of both voluntary contraction of the external sphincter and rectal sensation confirms that patients with complete supraconal lesions lose conscious control of sphincter activity.

6.   These observations reinforce the notion that the external anal sphincter response to increases in intra-abdominal pressure is a spinal reflex, triggered by tension receptors in the pelvis floor.

7.   Defecation requires the cortical inhibition of the external sphincter contraction in response to increases in intra-abdominal pressure.

8.   The external anal sphincter response to rectal distension is very closely associated with both rectal sensation and rectal contraction in normal subjects, and presumably acts to prevent soiling.

9.   These observations support previous conclusions that the external anal sphincter response to rectal distension is a spinal reflex, that has become extensively modulated by conscious mechanisms.