JAMES APJOHN, M.D. M.R.I.A. Professor of Chemistry to the Royal College of Surgeons in Ireland. R. ARROWSMITH, M.D. Physician to the Coventry

Dispensary.

EDWARD ASH, M.D. Physician to the Norwich Dispensary.

JAMES L. BARDSLEY, M.D. Physician to the Manchester Royal Infirmary, Dispensary, &c. EDWARD BARLOW, M.D. Physician to the Bath United Hospital and Infirmary.

THOMAS EDWARD BEATTY, M.D. Professor of Medical Jurisprudence to the Royal College of Surgeons in Ireland.

JOHN J. BIGSBY, M.D. F.L.S. Senior Physician to the Newark Dispensary, Foreign Member of the American Philosophical Society, Philadelphia, &c. &c.

J. BOSTOCK, M.D. V.P.R.S. F.L.S. F.G.S. &c.
JOSEPH BROWN, M.D. Physician to the Sunder-
land and Bishopwearmouth Infirmary.
THOMAS H. BURDER, M.D. Member of the Royal
College of Physicians, London.

JOHN BURNE, M.D. Physician to the Carey-street
Dispensary.

ROBERT CARSWELL, M.D. Professor of Morbid Anatomy in the University of London.

H. W. CARTER, M.D. F.R.S. E. Fellow of the Royal College of Physicians, London, Physician to the Kent and Canterbury Hospital. JOHN CHEYNE, M.D. F.R.S.E. M.R.I.A. Phy sician General to the Forces in Ireland, &c. JAMES CLARK, M.D. F.R.S. Physician to St. George's Infirmary, &c. &c.

HENRY CLUTTERBUCK, M.D. Physician to the General Dispensary.

JOHN CRAMPTON, M.D. M.R.I.A. King's Professor of Materia Medica, Physician to Steevens's Hospital, &c. Dublin.

ADAIR CRAWFORD, M.D. London.

ANDREW CRAWFORD, M.D. Physician to the Hamp-
shire County Hospital, Winchester.
WILLIAM CUMIN, M.D. Member of the Faculty of
Physicians, Glasgow.

JOHN DARWALL, M.D. Physician to the Birmingham General Hospital.

JOHN ELLIOTSON, M.D. F.R.S. Physician to St. Thomas's Hospital, and Professor of Medicine in the London University.

J. GILLKREST, M.D. Deputy Inspector of Hospitals, London.

GEORGE GOLDIE, M.D. Shrewsbury, late Physician to the York County Hospital.

GEORGE GREGORY, M.D. Physician to the Small Pox Hospital.

MARSHALL HALL, M.D. F.R.S. L.&E. &c. &c. THOMAS HANCOCK, M.D. Liverpool, Member of the Royal College of Physicians, London. CHARLES HASTINGS, M.D. Physician to the Worcester Infirmary, &c. &c.

BISSET HAWKINS, M.D. Fellow of the Royal College of Physicians, Professor of Materia Medica and Therapeutics in King's College, London.

J. HOPE, M.D. F.R.S. Member of the Royal College of Physicians, London, and Physician to the Mary-le-bone Infirmary.

JAMES HOUGHTON, M.D. Physician to the SouthEastern Dispensary, Dublin.

ARTHUR JACOB, M.D. M.R.I.A. Professor of Anatomy to the Royal College of Surgeons in Ireland.

CHARLES JOHNSON, M.D. Professor of Midwifery to the Royal College of Surgeons, Dublin. WILLIAM BRUCE JOY, M.D. Fellow of the King and Queen's College of Physicians in Ireland, Physician to the Dublin General Dispensary. WILLIAM KERR, M.D. Physician to the Northampton General Infirmary.

ROBERT LAW, M.D. Fellow of the King and Queen's College in Ireland, Physician Extraordinary to Sir Patrick Dun's Hospital.

ROBERT LEE, M.D. F.R.S. Physician to the British Lying-in Hospital.

CHARLES LOCOCK, M.D. Physician to the Westminster General Lying-in Hospital, &c.

H. MARSH, M.D. M.R.I.A. Professor of the Principles and Practice of Medicine to the Royal College of Surgeons in Ireland, &c. Dublin. WILLIAM F. MONTGOMERY, M.D. Fellow and Professor of Midwifery to the King and Queen's College of Physicians in Ireland.

J. A. PARIS, M.D. F.R.S. Fellow of the Royal College of Physicians, London.

J. C. PRICHARD, M.D. F.R.S. Physician to the Infirmary and to St. Peter's Hospital, Bristol. JONES QUAIN, M.B. Professor of Anatomy and Physiology in the London University. ARCHIBALD ROBERTSON, M.D. Physician to the Northampton General Infirmary.

P. M. ROGET, M.D. Sec. R.S. Consulting Physician to the Queen Charlotte's Lying-in Hospital and to the Northern Dispensary, &c. JOHN SCOTT, M.D. Edinburgh.

WILLIAM STOKES, M.D. Physician to the Meath Hospital, Dublin.

A. T. THOMSON, M.D. F.L.S. Professor of Materia Medica and Therapeutics in the London Univer.

sity.

THOMAS THOMSON, M.D. F.R.S. L. and E. Regius Professor of Chemistry in the University of Giasgow, &c.

T. J. TODD, M.D. Physician to the Dispensary, Brighton.

RICHARD TOWNSEND, M.D. M.R.I.A. Fellow of the King and Queen's College of Physicians, Dublin.

THOMAS WATSON, M.D. Fellow of the Royal College of Physicians, Physician to the Middlesex Hospital, and Professor of Medical Jurisprudence in King's College, London, &c. &c. JOHN WHITING, M.D. Member of the Royal College of Physicians, London, Physician to the Surrey Dispensary, &c.

CHARLES J. B. WILLIAMS, M.D. Member of the Royal College of Physicians, London.

EMETICS. (Þápμana iμerina, emetica; from w, vomo.) Emetics may be defined -substances which cause the ejection of the contents of the stomach by the mouth, independently of the stimulus of quantity, or of the influence of any nauseous taste or flavour. When these substances, with a few exceptions, are taken into the stomach in certain quantities, they do not immediately operate, but produce an uneasy sensation attended with nausea, which increases, and terminates in vomiting. Even before vomiting commences, the influence of the emetic substance is not confined to the stomach. As soon as the nausea is felt, the countenance becomes pale; and the pulse, diminished in strength and frequency, is quick and irregular. There is occasionally great anxiety, listlessness, and depression of spirits, with a tendency to fainting: at length sweat breaks forth, and just before vomiting commences, a peculiar sensation is experienced at the clavicles. After the vomiting has begun, the face flushes, the pulse is quickened, and it remains so betwixt each effort of vomiting, which occurs several times in succession, at short intervals, before it ceases. The nausea now subsides, either at once or by degrees, leaving a transitory feeling of depression, which makes the patient indifferent to every thing around him.

When emetic substances, with the few exceptions to which we have already alluded, are received into the stomach, they do not operate by any local stimulating influence on the coats of that organ; the time which elapses after they are swallowed sets aside such an opinion; and there exist other sufficient reasons for affirming that they are absorbed and carried into the circulation before vomiting is induced. When a solution of tartar emetic is injected into the jugular vein, it produces vomiting

VOL. II.

sooner than if it had been swallowed; and an experiment of M. Majendie has demonstrated that vomiting produced by an emetic substance may be stopped by pressure made upon the medulla oblongata. Now the inference that may be drawn from this fact is, that the action of emetics is not owing to any local stimulus on the nerves of the stomach, but to the action of the emetic substance, after being absorbed into the circulation, as a direct stimulus to the origin of the nerves, whereby contractions of the stomach, and the actions of the other muscles concerned in the act of vomiting, are induced. These nerves comprehend a branch of the eighth pair, the intercostal, and the phrenic nerves.

It may be inquired-what is the nature of the irritation which excites vomiting? Does it depend on the physical character of the particles of the substance employed? or is it the result of some chemical or electro-chemical change? These are queries which cannot be satisfactorily answered: all that can be said is, that there is, probably, something connected with the substances which cause vomiting, which has the power of irritating a particular set of nerves only: for, were this not the case, why should tartar emetic, when injected into the jugular veins, excite vomiting?

Vomiting may be produced by a variety of causes, either connected directly with the stomach itself, or indirectly, by sympathy with it through the medium of the nervous system.

1. Vomiting may be directly induced by food undergoing changes inconsistent with healthy digestion; by mechanical irritants lodging in the stomach; by tumours pressing on the pylorus; by inverted actions of the intestinal canal, forcing the contents of the duodenum, particularly the bile discharged into it from the biliary duct, into the stomach; by chemical acrids and other poisons, or emetic

B

substances taken into it; by any the mildest substances, when inflammation of its coats, or ulceration, augments its nervous irritability.

2. Vomiting may be indirectly induced by strangulations of the intestinal canal ; by the irritation arising from biliary or renal calculi impacted in the excretory ducts of the liver or of the kidneys; by titillation of the fauces; by inflammation of certain portions of the contents of the cranium, for example, of the arachnoid membrane covering the base of the brain; by repelled cutaneous eruptions; by emetic substances injected into the veins; by sailing, swinging, riding in a carriage, and other movements of the body; by pregnancy; by the influence of certain odours; and by mental impressions. Whichever of these causes produces vomiting, a specific action of the stomach, and the consent of certain muscles of the thorax and the abdomen are, in every instance, necessary to produce the effect: thence the question, in what manner is vomiting effected? In replying to this query, let us first inquire what opinions have been advanced regarding it by others.

M. Chirac first suggested the opinion that the stomach is passive during vomiting, which he contends is effected solely by the action of the diaphragm and the abdominal muscles; an opinion afterwards adopted by Duverney, Bayle, and John Hunter. M. Litre denied the influence of the abdominal muscles, and maintained that the diaphragm is the chief agent in producing vomiting. Lieutaud and Haller supported the idea that the stomach is the real agent; the former founding his opinion on having observed, in a patient who could not be made to vomit by the most powerful emetics, that the stomach was greatly distended and insensible. Sir Charles Bell+ appears to hold nearly similar opinions to those of Lieutaud upon this subject. "That vomiting," says he, " may be produced by the inverted motion of the stomach and diaphragm alone, is apparent from experiments upon living animals, where the abdominal muscles are laid open, and from cases in which the stomach has rested in the thorax, and yet been excited to active vomiting." He also states that the walls of a stomach in his possession "had become so thick that they could no longer suffer contraction by the muscular fibres; the consequence of which was, that although the inner coat of the stomach was in a raw and ulcerated state, there was no vomiting." Sir Charles, however, modifies this opinion by remarking," that when the stomach is excited to vomiting, there is consent of the abdominal muscles, by which they are brought into violent spasmodic action; not alternating in their action, as in the motion of respiration, but acting synchronously, so as greatly to assist in compressing the stomach; but," he adds, "at the same time, the action of these muscles, however forcible their contraction, cannot alone cause vomiting; nor has this action any tendency to produce such an

Histoire de l'Académie des Sciences, 1686. Anatomy of the Human Body, vol. iv. p. 54.

effect on other occasions, in which the utmost contraction of the diaphragm and abdominal muscles is required to the compression of the viscera."

M. Majendie, in an able memoir published in 1813, supports the opinion of Chirac.* In one of his experiments, he drew the stomach through an opening of the abdomen, thus freeing it from the influence of the diaphragm and abdominal muscles, and he found that vomiting could not be excited. He also ascertained that, if all the abdominal muscles be removed, leaving only the linea alba, vomiting still occurs from the stomach being pressed, as he supposes, between that part and the diaphragm. In another experiment he states that he substituted a pig's bladder for the stomach, and, nevertheless, vomiting took place! He found that the division of the phrenic nerve weakens the action of vomiting, but does not altogether prevent it.

These experiments prove-1. that the influence of the nervous system is essential to the production of vomiting; 2. that the abdominal muscles greatly influence the ejectment of the contents of the stomach. But they do not satisfactorily explain the action of the diaphragm, nor the part which the esophagus bears in the operation of vomiting. Dr. Richard Harrison, in his Gulstonian Lecture, adopts the opinions of Chirac and Majendie, as far as regards the action of the diaphragm and the abdominal muscles; but he adds to this call upon the expiratory muscles through the agency of the brain, and their consequent action, the contraction of the stomach itself. There can be no doubt of the agency of the nervous system in this operation; the only question is, whether the excitement be first exerted on the extremities of the nerves of the stomach itself, from which the impression is communicated to the brain by sympathy, and the auxiliary muscles be thus called into action: or whether, as the writer of this article imagines to be the case, the impression is made upon the spinal marrow from the absorption of the emetic substances, and through the influence of the motor nerves to the respiratory muscles, so that all the machinery concerned in the operation is excited into simultaneous action.

Dr. Marshall Hall has endeavoured to prove that Majendie's assertions respecting the influence of the diaphragm are incorrect, and that the act of vomiting is in fact a forcible expiratory effort. He contends that, if the diaphragm contracted, as Majendie affirms, the act of vomiting would be attended by inspiration; that the glottis, in such a case, would necessarily be open, and that the fluids ejected from the stomach would be drawn into the larynx, and induce great irritation there; an event which does not occur in vomiting. On the contrary, as M. Majendie admits, although he contends for the agency of the diaphragm, the larynx is accurately closed at the instant that the vomited matter is passing through the pharynx. Dr. Hall's explanation of the mechanism

See also Précis Elémentaire de Physiologie vol. ii. p. 140.