SUMMARY1. It has been ascertained experimentally that an open duodenal cannula does not cause any marked variation in emptying of the abomasum when compared to the rate of emptying of the normal viscus or when the cannulae are closed.2. Duodenal re-entrant cannulae provide a preparation whereby it is possible to infuse the duodenum via the distal cannula and to collect simultaneously the effluent fluid of the abomasum from the proximal arm of the cannula (Fig. 1).3. With this preparation the duodenal infusate is not contaminated by the gastric effluent and thus the duodenal stimulus can be restricted to the single non-varying effect of the infusate. 4. In the milk-fed calf using this preparation the following facts have been established.(a) On infusion into the duodenum, hypotonic and isotonic solutions of sodium chloride and sodium bicarbonate increase abomasal emptying; bicarbonate being the more effective stimulus.(b) Potassium chloride, calcium chloride, glucose and hydrochloric acid inhibit gastric emptying when infused into the duodenum.(c) Ammonium chloride, urea, lactose and acetic acid have little effect.

4. Glucose and lactose solutions inhibit abomasal emptying as well as acid production.5. Sodium chloride and sodium bicarbonate of low concentration, near isotonic with blood plasma, stimulate abomasal emptying but the bicarbonate is most effective. Hypertonic solutions of these salts inhibit abomasal emptying.6. Pepsin secretion in the abomasum of the calf is not affected by test meals of glucose, lactose, sodium chloride or sodium bicarbonate.7. These results shows a great similarity between the physiology of the abomasum of the milk-fed calf and the simple stomach. This suggests that the same duodenal receptors, discussed by Hunt & Knox (1968), which control gastric movement in man are also effective in controlling gastric emptying in the milk-fed calf.

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1. The abomasum of the milk‐fed calf has been examined using an adaptation of the Serial Test Meal method devised by Hunt & Spurrell (1951). The emptying process, acid secretion and pepsin secretion were studied. 2. Using serial test meals of simple solutions instilled into the abomasum via a cannula, our investigation leaves no doubt that the osmolarity of the abomasal contents significantly modifies the rate of abomasal emptying. 3. Hypotonic and isotonic solutions of sodium chloride and sodium bicarbonate increase abomasal emptying but bicarbonate is most effective. 4. Increasing the concentration of solutes in the abomasal contents slows abomasal emptying. Sodium chloride, sodium bicarbonate, ammonium chloride and urea do not delay abomasal emptying until hypertonic concentrations are attained. Hypotonic solutions of potassium chloride, calcium chloride, glucose, lactose, hydrochloric acid and acetic acid delay abomasal emptying. 5. The results obtained in the calf show that the abomasum is under restraint probably from duodenal receptors as is the simple stomach (Hunt & Knox, 1968) and that an osmoreceptor as postulated by Hunt (1956) is an important factor in this mechanism. 6. Acid secretion is inhibited when hypertonic solutions are instilled into the abomasum. 7. Pepsin secretion is not affected by simple solutions in the abomasum. 8. Gastric function in the milk‐fed calf appears to be controlled by mechanisms essentially similar to those already demonstrated in the simple stomach.

SUMMARY1. When the abomasum of the conscious calf is partially distended, rhythmic motility can readily be recorded from the e.m.g. of the smooth muscle of the fundus (body) and antrum.2. In gastric evacuation rhythmic contractions of the antrum are reinforced by both rhythmic and tonic fundic contractions.3. The output volume of the stomach can be directly correlated with e.m.g. activity.4. Intragastric fluid is usually emptied in gushes coinciding with a strong contraction of the antrum but fluid may be evacuated, when the antrum is inactive, through the force generated by persisting rhythmic fundic contractions.5. Using re-entrant cannulae so that the duodenum can be infused separately from the gastric effluent, isotonic sodium bicarbonate produced almost 100 % gastric evacuation with greatly enhanced e.m.g. activity of fundus and antrum. Infusion of the duodenum with a solution of HC1, 60 m-equiv/L., produced the opposite effect, the gastric muscle becoming quiescent and 100 % of the gastric test meal being retained.6. These results show that the activating or inhibitory effects of a duodenal infusate are produced through an activating or inhibitory effect on the smooth muscle of the stomach.7. The mechanism of the interrelation between duodenal receptor and gastric effector has not yet been elucidated but the connexion is not intramural since it continues when the duodenum is transacted near to the pylorus.