VOMITING. 629 



conveyed to the brain by the optic nerves, and from that organ the 

 sensation must emanate. It is probable, too, that when emetics are 

 injected into the veins, the first effect takes place on the brain, and the 

 stomach is affected secondarily. 



When the state of nausea, howsoever induced, continues for any 

 length of time, it is usually followed by vomiting. The rejected mat- 

 ters are generally from the stomach; but if the retching or violent 

 contractile efforts of the muscles concerned be long continued, the con- 

 tents of the small intestine also form part ; hence, we account for the 

 universality of the presence of bile in the rejected matters after an 

 emetic has been taken. Its presence is, therefore, in the generality of 

 cases, no evidence of the person's being what is termed bilious. The 

 contents of the small' intestine are returned into the stomach by the 

 antiperistaltic action. The longitudinal fibres take their fixed point 

 below, and contract from above downwards ; so that the chymous mass 

 is forced towards the upper part of the canal, whilst the circular fibres 

 contract from below to above. In cases of colica ileus or iliac passion, 

 the inverted action extends through the whole intestinal canal; so that 

 faecal matters, and even substances injected into the rectum, pass the 

 ileo-csecal valve, and are discharged by the mouth. 



Of old, it was universally maintained, that vomiting is caused by the 

 sudden and convulsive inverted contraction of the stomach ; and they, 

 who admitted that the diaphragm and abdominal muscles take part in 

 the action, looked upon them simply as accessories. Francis Bayle, 1 

 Professor in the University of Toulouse, in 1681, appears to have been 

 the first who suggested, that the stomach is nearly passive in the act ; 

 and that vomiting is caused almost exclusively by the pressure exerted 

 upon that organ by the diaphragm and abdominal muscles. His reason 

 for the belief was founded on the fact, that having introduced his finger 

 into the abdomen of a living animal whilst it was vomiting he could not 

 perceive any contraction of the stomach. In 1686, M. Chirac repeated 

 the experiment with similar results ; after which, the views of Bayle 

 were embraced by many of the most eminent physiologists and patho- 

 logists, Senac, Van Swieten, and Schwartz, 2 and, at a later period, 

 by the celebrated John Hunter, 3 who maintained, that the contraction 

 of the muscular fibres of the stomach is not essential to the act. Many 

 distinguished physiologists ranged themselves on the opposite side. 

 M. Littre maintained, that the stomach is provided with considerable 

 muscular bands, capable of powerful contraction ; and that vomiting, 

 as in the case of ruminant animals, is often caused without the partici- 

 pation of the abdominal muscles. We have seen, however, that the 

 rumination of animals more resembles regurgitation. M. Lieutaud 4 

 argued, that, according to Bayle's theory, vomiting ought to be a vo- 

 luntary phenomenon; that the stomach is too deeply seated to be com- 

 pressed, so as to empty it of its contents, by the neighbouring muscles; 



1 Problemata Medico-physica et Meclica, Hagae Comitis, 1678. 



2 Haller, Elementa Physiol., lib. xix. 4, Bern., 1764. 



3 Observations on certain parts of the Animal Economy, with Notes by Prof. Owen, Amer. 

 edit., p. 121, Philad., 1840. 



4 Memoir, de 1'Acad. pour 1752, p. 223. 



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