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A study of the function of the lower end of the oesophagus in the cat confirms that it behaves as a true physiological sphincter, even though histological evidence for such a structure is absent. Sphincteric action is a function of the circular muscle fibres in the lowest 2 cm. of the oesophagus. Reflex changes in tone of the sphincter are mediated through the autonomic nervous system. The effects of possible neurohumoral transmitters, nerve stimulation, and antagonists have been studied.
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Clark et al. (1961) studied this question.
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