Some observations on the behaviour of isolated and interposed jejunal and ileal segments in the rabbit

Segments of jejunum and distal ileum of varying lengths and different vascular supply were isolated and interposed iso‐ and antiperistaltically. Pressures proximal to the interposed segment were recorded with a fine, soft, open‐tipped cathether introduced via a Mann‐Bollman fistula. 1. The distal ileal segments supplied by a single vessel exhibit an unpredictable high degree of tone in some cases, and when these segments were interposed they caused a high degree of partial obstruction irrespective of whether they were interposed iso‐ or antiperistaltically. Distal ilcal segments supplied two or more vessels interposed antiperistaltically caused a degree of obstruction related to their lengths, and interposed isoperistaltically they caused no obstruction. 2. Jejunal single‐vessel segments of both polarities exhibited low obstructive qualities. Antiperistaltic jejunal segments of two or more vessels supply behaved in a similar manner to corresponding ileal segments in that the degree of obstruction was related to the length of the segment. Isoperistaltic segments supplied bt two or more vessels caused no obstruction. 3. Possible mechanisms accounting for the differing findings in jejunum and ileum are discussed. 4. Some clinical applications are discussed.