The functions of the large intestine / W.B. Cannon.

  • Walter Bradford Cannon
Date:
1912
Catalogue details

Licence: Public Domain Mark

Credit: The functions of the large intestine / W.B. Cannon. Source: Wellcome Collection.

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    and the excretion of its residue may vary when the bowels are opened regularly once a day, between nine and thirty- two houts—the period depending on the time of eating and the time of defecation. ‘ INNERVATION OF THE LARGE INTESTINE The large intestine receives, like the stomach and small intestine, a double nerve-supply from the central nervous system—a tonic or motor supply through the sacral visceral nerves, and an inhibitory supply from the lumbar cord through the, sympathetic system, by way of the inferior mesenteric ganglion. According to Elhott and Barclay-Smith the sacral visceral nerves do not innervate the proximal third of the colon in the cat or the cecum in the dog. Indeed, the regions of anastal- sis seem not to receive motor impulses. The functioning of the two sets of nerves is indicated by the results of sectioning, as well as by stimulating them. Severance of the sympathetic fibers in the cat and rabbit causes no lasting disturbance of the motor func- tions. After removal of the motor impulses, however, by destruction of the sacral cord or by cutting the nerves, feces accumulate and the contractions of the intestine are weak and sluggish.2! These functional defects may be due to the persistence of inhibitory tonus, for when both sets of nerves are abolished in the dog, the animal, after a few weeks, exhibits normal activity of the colon, with feces of usual consistency discharged at customary intervals. CONSTIPATION As already stated, defecation is a reflex initiated by the presence of feces in the rectum. The section of sensory roots of the sacral nerves supplying the rectal mucosa causes an abolition of the normal coordination.** It is a matter of much practical importance that the rectal mucosa soon becomes adapted to the presence of a fecal accumulation, and then fails either to induce the desire to defecate or to initiate reflex contraction of the colon. If the call to defecation is not promptly obeyed, therefore, it ceases to be given, and the feces stagnate in the rectum. 21. Elliott and. Barclay-Smith: Jour. Physiol., 1904, xxxi, 288. 29. Merzbacher: Arch. f. d. ges. Physiol., 1900, Ixxxi, 474.
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