Abstract
In a preceding communication an apparently unknown spindle-shaped structure in the rabbit was described, which connects the transverse colon with the descending colon. Evidence was submitted which proved that this section of the gut forming the spindle was anatomically and functionally different from the neighboring transverse and descending colon. It was shown in brief that this organ was slightly curved, spindle shaped, 4.5 to 8.5 cm. in length along the greater curvature, provided with a sphincter towards the descending colon side, devoid practically of any mesentery, more pink and thicker-walled than either the ascending or the transverse colon, with a thick, smooth mucosa arranged in longitudinal folds, and quite different from that found in adjoining sections of the gut. It was emphasized that the scybala found in normal rabbits towards the ascending colon side were large, grayish, soft and rich in water, while those immediately below the sphincter in the descending colon, were smaller, grayish yellow, hard and dry.
Functionally the organ behaved as follows in a morphinized rabbit after laparotomy: the intravenous injection of 0.1 to 0.3 mg. of physostigmin caused well marked peristalsis in the ascending and transverse colon. As the wave of contraction reached approximately the middle part of the spindle, the neck of the spindle contracted powerfully and antiperistaltically, preventing the passage of the scybalum. The peristaltic wave relaxed first, and the contents of the bulging portion between the two constrictions is pushed back antiperistaltically by the maintained or increasing antiperistaltic contraction of the sphincter area. After this the sphincter area relaxes slowly. This phenomenon is repeated several times, and occasionally gas and liquid can be seen passing through the narrowing sphincter. Finally, however, the antiperistaltic contraction wave at the neck relaxes before the peristaltic contraction advancing from the transverse colon, and then the contents of the spindle is pushed into the dilating thin-
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