Nervous Control of Stomach Movements in Dogfishes and Rays

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Abstract
The organization of the alimentary canal of fishes differs greatly between species of different dietary habit, but is not well understood. The vagus and sympathetic systems are very different in elasmobranchs and teleosts, but there has been little work on the corresponding physiology and pharmacology. The digestive system of elasmobranchs has unusual features connected with the fact that the absorbtive surface is provided by the spiral intestine (Fig. 1). This is a short fat tube whose surface is greatly increased by the presence of a coiled fold, the spiral valve. This arrangement provides a large area for absorbtion, neatly packed, but it leaves only a narrow lumen, so that no large particles can pass along the spiral intestine. Presumably it is in connexion with this condition that the stomach is divided into two parts. The cardiac division is a large sac into which the prey is received whole, its wall is very glandular and much breakdown of the food proceeds there (Hogben, 1967). The pyloric division is a narrower tube, leading from the hind end of the cardiac part to the pylorus.

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