STUDIES ON THE FUNCTION OF THE INTESTINAL MUSCULATURE. II. THE VARIATIONS IN RATE AND CHARACTER OF THE NORMAL MOVEMENTS IN DIFFERENT REGIONS OF THE INTESTINE

¹ Department of Physiology, Medical College, Madras, South India

1. The rates and amplitudes of rhythmical contractions observed in excised segments from different regions of the bowel, and those observed in the intact bowel (cat) are analysed and examined. The records obtained with excised segments show the longitudinal muscle contractions best, the balloon records of movements in the intact bowel the circular muscle contractions best.

2. The rate of rhythmical contraction in the two muscle layers shows a definite gradation down the bowel. This corroborates the view of Alvarez and earlier observers.

3. The cause of the gradient in rhythm is discussed. It is pointed out that the gradient in rhythm cannot be due to a basic metabolic gradient as Alvarez first suggested, nor separated from the gradient in irritability as he more recently suggested. It is concluded that the gradient in rhythm is the result of a gradation in the tonus of the muscle layers. It is accompanied by a gradation down the bowel in the size and number of nerve-cells and fibres in Auerbach's plexus.

4. The amplitude and force of the contractions seem to depend not only on the degree of tonus and muscular thickness in the different regions, but also on the pressure within the bowel. The longitudinal muscle in the upper bowel has a tendency to show a greater amplitude in excised segments, while the circular muscle shows, with a high pressure from within, a greater amplitude and force in the upper bowel, and with a low pressure a greater amplitude in the lower bowel (ileum).

5. The normal direction of peristalsis from the oral to the caudal end of the small intestine is determined by the gradation in muscular strength, tone, and irritability.

I wish to express my thanks to Messrs C. K. Prasada Rao and C. Vareed for technical assistance in carrying out the experiments.