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SUMMARYThe aim of this study was to determine the mechanisms controlling gastric emptying of viscous meals. In four conscious dogs the antral, pyloric and duodenal activities were recorded with strain-gauge transducers and induction coils during gastric evacuation of an inert cellulose meal and of four nutrient meals containing mannitol, casein, glucose or oleic acid. Gastric emptying and the internal pyloric and duodenal diameters were measured from radiographs. The nutrients delayed gastric emptying and diminished to a various extent the antral and duodenal motility as well as the pyloric opening. The motility gradient between antral and duodenal activity showed no relationship to the emptying delay. The duodenal lumen was reduced and the propulsive contractions of the duodenum decreased while the segmental activity increased. The findings suggest that gastric emptying is controlled by (1) the depth of the antral waves, (2) the pyloric opening, (3) the receptive relaxation of the duodenum and (4) the type of the duodenal contractions. By contrast the sequence of the terminal antral contraction and the pyloric closure, as well as the co-ordination between pyloric and duodenal contractions, played no important role in regulating gastric emptying.

SUMMARY1. Rabbits produce hard and soft faeces in a circadian rhythm. This study was undertaken in order to examine the motor function of the colon in relation to the formation of these two types of faeces.2. Colonic motility was measured in unanaesthetized rabbits using strain-gauge transducers and simultaneous radiography.3. Three types of contractions were found in the rabbit proximal colon: haustral activity, segmental activity, and mass peristalsis. Distinctly different motor patterns were observed during the formation of hard and soft faeces.4. When hard faeces were produced, the motor activity of the proximal colon was enhanced. It consisted ofsegmental and haustral activity. The segmental contractions separated the digesta into faecal pellets and forced them slowly aborad, whereas the movements of the haustra carried the liquid contents back towards the caecum.5. When soft faeces were produced haustral and segmental activity was reduced and transfer of the digesta through the proximal colon was accelerated by mass movements.6. In contrast to the proximal colon, the motility of the distal colon was enhanced during the formation of soft faeces and decreased during the production ofhard faeces.7. The results support the concept that hard faeces are chiefly produced by a separation of liquids and solids and by a retrograde transfer of liquid digesta rather than by an increased absorption of water.

In the canine small intestine several simple (S) and complex (C) patterns of propulsive and nonpropulsive activities were found. The nonpropulsive activity consisted of 1) stationary individual contractions (S) and 2) stationary clusters of contractions (C). Patterns leading to aboral propulsion of luminal contents were 1) propagating contractions (S), 2) propagating power contractions (S), 3) phase III of the migrating motor complex (C), and 4) migrating clusters of contractions (C). The propagation velocities of the propulsive motor patterns differed markedly; they increased in the following order: phase III, migrating clustered contractions, propagating power contractions, propagating contractions. A retrograde transport of luminal contents was produced by two different activities: 1) retrograde propagating contractions (S) and 2) retrograde power contractions (S). They were accompanied with enterogastric reflux.

SUMMARY In five conscious dogs motility of the antrum, pyloric sphincter, and duodenum was recorded with strain gauge transducers and induction coils. Gastric evacuation of low, medium, and high viscosity meals was measured via a duodenal cannula and observed simultaneously by radiography. Computer analysis of the propagation of the gastric waves revealed increased velocity in the distal antrum but no simultaneous contractions of the terminal antrum and pyloric sphincter. Radiography showed, and measurements of the antral diameter confirmed, that the indentations of the gastric waves were significantly deeper with the low viscosity liquid meal compared with the medium and high viscosity meals. Thereby, retropulsion of the medium and high viscosity ingesta was produced. Results indicated that gastric evacuation was regulated predominantly by the depth of the peristaltic indentation, which depended on the viscosity ofthe gastric contents. Nothing indicated that the phasic contractions of the pyloric sphincter were of importance for the regulation of gastric emptying.In previous studies on rabbits' it was found that gastric evacuation depended on the viscosity of the test meals. These findings were in agreement with the results of other groups which have measured gastric emptying of solid particles and of liquids labelled with isotopes.3-7 However, little is known about the different mechanisms involved in the gastric emptying of liquids and solids. Dozois et aL8 and Wilbur and Kelly9 studied the effect of antrectomy and vagotomy on gastric emptying of liquids and of radiopaque plastic spheres in dogs. They concluded that the gastric emptying of liquids is regulated by the proximal stomach, whereas that of solids is regulated by the distal stomach. The simultaneous contractions of the terminal antrum and of the pyloric sphincter produced retropulsion as described in dogs'0 and in humans."-'3 Thereby, the plastic spheres were retained in the stomach, while liquids were emptied very quickly. These results support the idea ofCannon'4 that the pyloric sphincter is the 'keeper of the gate'. However, it is doubtful whether the evacuation of large plastic spheres represents the emptying pattern of normal food. Moreover, these results are largely based on fluoroscopic observations. Exact measurements of Our objective was to clarify the mechanism by which gastric evacuation of liquid and visc us ingesta is regulated. This was accomplished by simultaneous radiography, recording the gastric and duodenal motility, and measuring the gastric evacuation.The study was part of a dissertation.'5 An abstract of the results was presented at the 7th

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SUMMARYIn five dogs gastric emptying of low, medium and high viscosity meals was measured via a duodenal cannula. The rate of emptying depended on the viscosity of the test meals: the time for half emptying was 45+22min with the low viscosity liquid meal (I centipoise), 28-9 + 9 5 min with the test meal of medium viscosity (105 centipoise), and 43 + 11 8 min with the test meal of high viscosity (106 centipoise). The emptying curves of the medium and high viscosity meals were sigmoid, whereas the curve representing the emptying of the low viscosity liquid meal followed an exponential pattern. Results indicate that the viscosity of the meal is an important factor for the rate of gastric emptying.

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