If the diaphragm received only diaphragmatic nerves, it would be easy to resist the contraction of this muscle by dividing these nerves; but it also receives filaments from dorsal pairs, and these filaments are sufficient to support its contractions. Yet experiment shows us, that the diaphragmatic nerves being cut, the contraction of the diaphragm is very evidently diminished in power, and it may be said, without much hazard of mistake, that this muscle loses, by this division, three quarters of its contractile force. It was then useful to see what influence the division of these nerves would have on the production of this phenomenon. I made this division in the neck of a dog of three years old, and I afterwards injected into the jugular vein three grains of emetic; there was only a very feeble vomiting; another injection of emetic, a quarter of an hour after, excited no vomiting. I opened the abdomen and endeavoured to produce vomiting by compressing the stomach. The compression, though very powerful and long continued, excited no effort of vomiting; it did not even appear to produce nausea. I thought that this circumstance might be owing to the idiosyncrasy of the animal; but having many times since repeated this experiment, I have never obtained any other result. In order to understand what part the abdominal muscles by their contractions take in vomiting, we ought to observe what takes place when these muscles are unable to act. There is but one way of coming at this, which is, to separate these muscles from their attachments at the sides of the linea alba; this we have done on many animals; we have detached successively the external oblique, the internal oblique and the transversalis, leaving on the anterior face of the abdomen only the peritoneum. When these muscles are thus removed, we can see very distinctly through the peritoneum, all that takes place in this cavity; we distinguish, for example, perfectly the peristaltic motion of the stomach and the intestines; and if the stomach contracts it will be easy to see it. The abdominal muscles being thus detached, I injected three grains of emetic into the jugular vein, and also immediately nausea and vomiting took place by the contraction of the diaphragm alone. It was curious to see, in the convulsive contraction of this muscle, the whole intestinal mass pushed downwards, and pressing strongly against the peritoneum, which was ruptured in some places. In this case, the linea alba, formed by a very strong fibrous texture, is the only part which resists the pressure of the viscera; its existence then is indispensable to the action of vomiting; perhaps it performs an analogous office in the ordinary state. This experiment proves that vomiting can be produced by the efforts of the diaphragm alone; this is also confirmed by the following experiment: