When Bichat wrote this work, hardly any thing of the motions of the œsophagus was known, except from the writings of Haller, who made but four experiments on the subject. I wished to observe them myself, and I have discovered many facts which I think interesting; I shall relate them here as I described them in a memoir read to the Institute in 1813. Before attempting to ascertain what part the œsophagus took in the passage of the food, it was proper to ascertain its state when it was supposed to be at rest. In the first experiments, I noticed an important phenomenon, and which hitherto had escaped the observation of physiologists, viz., that the lower third of the œsophagus has constantly an alternate motion of contraction and relaxation, which appears to be independent of all foreign irritation. This motion appears to be confined to the portion of the tube which is surrounded by the plexus of nerves of the eighth pair, that is to say, to about its lower third; there is no trace of it in the neck nor in the superior part of the thorax. The contraction appears like a peristaltic motion, it begins at the junction of the superior two thirds with the inferior third, and is continued to the insertion of this tube in the stomach. When the contraction is once produced, it continues for an uncertain time; usually it is less than half an hour. The œsophagus contracted in this way in its lower third is hard like a cord powerfully stretched. Some persons whom I have made feel of it in this state have compared it to a rod. When the contraction has lasted the time I have just mentioned, the relaxation takes place suddenly and simultaneously in each of the contracted fibres; in some cases, however, the relaxation seems to take place from the superior fibres towards the inferior ones. The œsophagus examined during the state of relaxation exhibits a remarkable flaccidity, which contrasts wonderfully with the state of contraction. This alternate motion is dependent on the nerves of the eighth pair. When these nerves are cut in an animal, this motion entirely ceases; the œsophagus contracts no more, but it is not in a state of relaxation; its fibres without the control of nervous influence shorten; it is this which produces, so far as the touch is concerned, an intermediate state between contraction and relaxation. When the stomach is empty or half full of food, the contraction of the œsophagus recurs at much longer intervals; but if the stomach be powerfully distended by any cause, the contraction of the œsophagus is usually very powerful, and continues for a much longer time. I have seen it, in cases of this kind, continue more than ten minutes; under the same circumstances, that is to say, when the stomach is excessively full, the relaxation is always much shorter.