New evidence is presented to clarify to some extent the significance of the gradient of rhythmicity in the small intestine of the unanesthetized dog. The gradient of rhythmicity was studied on five dogs prepared with duodenal fistulas. Rhythmic contractions were recorded from the small intestine by a small rubber balloon. The gradient of rhythmicity was found to decrease in a stepwise manner as the distance from the pylorus is increased. Roughly, the rhythmic contractions were found to be 18 to 19 per minute in the duodenum and 14 to 15 per minute in the ileum. In the terminal ileum there was somewhat of a reversal in the gradient of rhythmicity.

Additional evidence is presented to suggest that a duodenal pacemaker controls the normal frequency of contractions in the jejunum and in the ileum. The effects of hot and cold water, applied above or below the level of the fistula, on the frequency of contractions recorded at various levels were studied. The duodenum was locally heated or cooled either directly by applying water through a finger cot attracted at the end of a Miller Abbott tube. During local cooling of the duodenum the average frequency of contractions recorded at 50, 100 and 150 cm. for all five dogs decreased 3.5, 2.6 and 1.7 beats per minute, respectively. The effects of local heating applied to the duodenum in most instances gave no significant results.

In a few preliminary experiments combined mechanical and electrical activity were recorded from the mucosal surface of the small intestine. The typical slow waves were recorded using an electrode-bearing balloon. Slow waves were recorded in the absence of apparent mechanical activity. These slow waves corresponded in frequency with the mechanical contractions when they were present.

LLU Discipline





Graduate Studies

First Advisor

J. Earl Thomas

Second Advisor

Guy M. Hunt

Third Advisor

Robert W. Woods

Fourth Advisor

Robert B. Pearson

Fifth Advisor

Don R. Goe

Degree Name

Master of Science (MS)

Degree Level


Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

Intestine, Small



Page Count

vi; 45

Digital Format


Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.


Loma Linda University Electronic Theses and Dissertations

Collection Website



Loma Linda University. Del E. Webb Memorial Library. University Archives