The process of vomiting serves to empty the stomach of its contents by the shortest way, that is, through the oesophagus and mouth. The mechanism of this action is very complicated and a large number of striated and non-striated muscles participate in it. At first the abdominal muscles and the diaphragm contract and compress the. abdominal cavity; then the stomach contracts and the pylorus closes firmly. At the same time the longitudinal fibres of the lower end of the oesophagus contract and open the cardia; the pressure which is exerted by the stomach upon its contents throws them into the open oesophagus, which becomes wider and shorter by the contraction of its longitudinal fibres. The epiglottis turns upon the larynx and closes up this canal, while the soft palate rises and covers the posterior nares. Both these actions serve to prevent the contents from reaching either the larynx or the nasal cavity. The only canal which remains open is the mouth. From the oesophagus, by an antiperistaltic contraction of the same, the contents are quickly emptied through the mouth. It is generally believed that there exists a centre for the act of vomiting in the vagus nucleus.

It may even be that the respiratory centre and the centre for vomiting are situated at one and the same spot.

1 Poosgen "Die motorisehen Verrichtungen des menschlichen Magens." Strassburg, 1882, p. 127.

Vomiting may be a consequence of various pathological conditions of the stomach, or may be due to an abnormal state of the food. Nervous vomiting is characterized by the absence of either of the two conditions mentioned.

The vomiting may be due to some spinal or cerebral irritation, or may originate reflexly from abnormal conditions in other organs (pharynx, oesophagus, larynx, palate, kidneys, liver, peritoneum, genital organs, etc.), or it may be due to neurasthenia or hysteria. Among these different kinds of nervous vomiting juvenile vomiting and the periodic vomiting of Leyden1 deserve special consideration.

1 E. Levden: l. c.

Diagnosis

The diagnosis of nervous vomiting has a twofold object in view: (1) To recognize the nervous character of the condition, and (2) to reveal, if possible, its cause. Stiller1 gives the following points as characteristic of nervous vomiting: It occurs easily, without any effort and without any preparatory stage. It is, as a rule, independent of the quality and quantity of the ingested food. Other points he mentions are: The capriciousness with which certain kinds of food (sometimes very easily digestible) are ejected, while other indigestible substances are well borne; the faculty which sometimes exists in selecting only one certain substance from the various food-stuffs present in the stomach for the vomiting; the carelessness with which the patients bear this condition for a long time; the very slight or hardly marked degree of inanition, notwithstanding the long duration of the ailment. The vomiting is not always dependent upon the meals, but may occur occasionally in the fasting condition. There exist other neuropathic symptcnis, which may be associated with the vomiting or alternate with it - the influence which psychical conditions exert upon the vomiting. To these points Boas2 adds another one, namely, normal secretory and motor functions of the stomach.

I agree, however, with Bouveret that, while this may be present in some cases, there certainly occur cases of nervous vomiting in which the gastric secretory function is greatly diminished or even absent.