Normally, vomiting is due to irritation of the endings of the vagus nerve in the stomach, although the afferent impulses may have other sources. Touching the upper surface of the epiglottis with the finger will provoke the reflex. So also will stimulation of the olfactory nerves by a foul smell. In this latter case the emotion of disgust to which the odour gives rise brings about the reflex action. A flow of saliva precedes the act of vomiting. A deep inspiration is then taken, in order that for a time the lungs may be independent of a fresh supply of air. The glottis is closed, the diaphragm fixed. Contraction of the abdominal wall presses the stomach against the diaphragm; its cardiac sphincter relaxes, and its contents are squirted into the œsophagus, which undergoes a forcible retrogressive peristalsis. It is interesting to note the difference between carnivora and herbivora in regard to vomiting. Carnivora swallow fur and other indigestible materials, as well as many unwholesome things which they need to be able to return. A dog can, apparently, vomit at will. Never, while in a state of nature, do herbivora need to return the contents of the stomach. No provision is made for vomiting. A heifer which has strayed into a dewy clover-field is not unlikely to die from the effects of distension of its paunch, if relief be not given by opening it with a knife. In a horse the cardiac sphincter is strong, the pyloric weak. Pressure on the stomach tends to drive its contents through the pyloric valve into the duodenum, not backwards into the œsophagus. The stomach is not so placed as to allow of its being compressed between the wall of the abdomen and the diaphragm. Horses cannot vomit. It is a mistake to suppose that they suffer from sea-sickness. In rough weather they sweat, their limbs tremble, they go off their feed; but these symptoms are probably due to the fatigue which results from excessive anxiety to maintain their balance, and to fear. We can never know their feelings, but there is no reason for supposing that they experience the sensation of nausea.