THE INFLUENCE OF NATURAL CHEMICAL STIMULI ON THE MOVEMENTS OF THE FROG'S STOMACH

¹ The Physiological Laboratory, University of Odessa

1. The most active part of an isolated stomach of the frog is the pyloric part, from which both ascending and descending waves of contraction may arise.

2. The influence of hydrochloric acid on the spontaneous contractions of a frog's stomach varies according to the concentration of the solution employed. In weak solutions (0·05 per cent.) hydrochloric acid increases the contractions while diminishing their frequency. In more concentrated solutions (0·1 per cent. to 0·2 per cent.) it weakens or arrests them. In the latter case a marked lowering of tone is observed.

3. The pyloric part of the stomach is the most sensitive to hydrochloric acid.

4. The effect of sodium carbonate (0·3-0·5 per cent.) is to raise the tone and to increase the intensity and frequency of the contractions of the frog's stomach.

5. The effects of sodium carbonate vary with the excitability of the neuro-muscular apparatus of the stomach. On weakened preparations what is observed is principally a rise in tone; but—with sufficient excitability of the preparation—special "sodium" contractions are caused.

6. Sodium carbonate, unlike hydrochloric acid, stimulates the activity of the pyloric part.

This investigation was begun in 1918 in the Physiological Department of the Institute of Experimental Medicine in Petrograd, and was finished in the Physiological Laboratory of the University of Odessa. I owe a debt of gratitude to Professor I. P. Pavlov, not only for allowing me to work in his Laboratory, but also for his helpful criticism throughout the work.