10 ounces of this water, or 4375 grains, therefore, contain

4.4

0.07

0.3

8.4

2.52

57.00

4302.30

4375.00

The striking facts relating to this mineral water are its existence at such a great altitude, and the presence of hydriodide of potassa in it. We know that muriatic acid does not decompose the hydriodides; we are not, therefore, surprised to find hydriodide of potassa in waters in which the muriate of soda exists; but the sulphuric acid does decompose them; its affinity for soda is less than for potassa, with which the hydriodic acid is here combined, and yet it would appear that no change is effected by double decomposition. With abundance of carbonate of soda, and the sulphate of the oxide of sodium in solution with hydriodide of potassa, we should expect, in the order of affinities, to find the hydriodic acid united with the soda, and the sulphuric acid to retain the potassa; this, therefore, seems an exception to a general rule. Thenard states, in his System of Chemistry, that iodine has never been found to exist in nature but in the state of iodide of potassium. It is surprising that this water does not contain a single atom more of potassa than is held in combination by the hydriodic acid, and it seems to countenance the opinion that iodine does not naturally exist. but in combination with potassa.

Earthy Bitumen, called Murindó.

This substance is found at Murindó, near Navitá, in the Province of Chocó, in Colombia. It takes its name from the village of Murindó.

It is externally of a blackish brown colour; when broken, the fracture is earthy and uneven, and the colour of the fractured part is much lighter. It yields to the nail, and is sectile; it is dull, and leaves a mark on paper: when in powder, it has a pungent smell; the taste is hot and peculiar. Before the blowpipe, it first ignites, and burns with a thick smoke, leaving a shining black coal. The smoke, whilst burning, has the pleasant odour of benzoin.

Examination of this Substance.

Specific gravity less than water.

2000 grains of distilled water at 60° Fahrenheit dissolve three grains of this substance; alcohol of specific gravity 82, at 60° Fahrenheit, dissolves a considerable quantity of it, and forms a red tincture.

Water decomposes this tincture and precipitates resin. It has not any tannin.

Benzoic acid may be obtained from it by sublimation. This substance consists of altered resin, benzoic acid, and earth, and appears to be produced by the decay and carbonization of some tree containing benzoin, of which there are many in Colombia. It is used by the natives medicinally as a styptic or astringent. In this particular the Indians follow the Persians, in the country of which people a similar substance exists, and is so highly prized for its medical virtues, as to become royal property. Murindó resembles, in many respects, this bituminous earth from Persia.

On the Mechanism of the Act of Vomiting. By MARSHALL HALL, M.D., F. R. S. E., &c. &c.

Two opinions have divided physiologists respecting the nature of the act of vomiting. It was originally and long thought that this act consisted simply in a sudden and forcible contraction of the stomach itself. Afterwards Bayle, and Chirac, and more recently M. Majendie, considered that the stomach is inactive, and evacuated by being subjected to pressure by the simultaneous contraction of the diaphragm and abdominal muscles.

It appears to me that neither of these opinions is correct. M. Majendie distinctly proves by actual observation, and by the substitution of a bladder in the place of the stomach, that the contraction of this organ is not usually subservient or necessary to the act of vomiting. I refer to the interesting paper* of that eminent physiologist for the more full elucidation of this first question. I proceed to state such observations as appear to me to controvert the second, and to establish that view of this subject which I have myself been led to adopt.

* Mémoire sur le Vomissement, par M. Majendie. A Paris, 1813.

It is obvious that, if vomiting were effected by a contraction of the diaphragm, it must be attended by inspiration. If this were the case, the fluids ejected from the stomach would be drawn into the larynx, and induce great irritation, events which are not observed. These events are, indeed, effectually prevented by an accurate closure of the larynx, a fact observed in an actual experiment by M. Majendie, who makes the following observation :-" Dans le vomissement, au moment où les matières vomies traversent la pharynx, la glotte se ferme très-exactement *." It is astonishing that this observation did not lead its acute author to see that, under such circumstances, a contraction of the diaphragm, unless the thorax followed precisely pari passu, was impossible.

Complete vomiting has been observed, too, in cases in which the stomach had entirely passed through a wound of the diaphragm into the thorax, and in which it could not, consequently, be subjected to the action of that muscle †. In some experiments, vomiting was observed also to take place, although the diaphragm had been paralysed by a division of the phrenic nerves, or its influence subtracted by a division of its anterior attachments 1.

This view of the subject is still further confirmed by facts, which I now proceed to state, which prove that the act of vomiting is an effort, not of inspiration, but of expiration. This is obvious enough, indeed, on a mere observation of the state of the thorax and abdomen during vomiting. The larynx is evidently abruptly and forcibly closed, the thorax drawn downwards, and the abdomen inwards.

Such, indeed, appears to me to be the precise nature of the act of vomiting, in ordinary circumstances. The contents of the thorax and abdomen are subjected to the sudden and almost spasmodic contraction of all the muscles of expiration, the larynx being closed so that no air can escape from the chest, and the two cavities being made one by the floating or inert condition of the diaphragm. The mere mechanism of the act of vomiting differs little, therefore, from that of cough* Mémoire sur l'Usage de l'Epiglotte dans la Déglutition, p. 3, note.

Such a case is mentioned by Wepfer. A similar one was also recently witnessed by Dr. Webster and Mr. Hunt. The whole of the stomach was found in the thorax, having passed through a wound of the diaphragm. There was repeated vomiting of a substance resembling coffee-grounds.

Œuvres de Car. Legallois. A Paris, 1824, tom, ii.

p.

104.

ing, by which, indeed, the contents of the stomach are frequently expelled: the larynx, in the former, is, however, permanently, -in the latter, only momentarily closed; and there is, doubtless, a different condition of the cardiac orifice and of the oesophagus. It appeared to me, from these views of this subject, that, if an opening were made into the trachea, or through the parietes of the thorax, the effort of expiration constituting the act of vomiting, would issue in expelling the air through these orifices respectively, and the evacuation of the stomach would be prevented; and I determined to submit the fact to the test of experiment. I took a little dog, made an ample opening into the windpipe, and gave a few grains of the sub-sulphate of mercury. The animal soon became sick. The first efforts to vomit induced a forcible expulsion of air through the orifice in the trachea. These efforts soon became very violent, however, and the stomach at length yielded a part of its contents. It was perfectly evident that the violent contractions of the abdominal muscles pressed upon the viscera of the abdomen so as to carry the diaphragm upwards to its fullest extent, and that at this moment vomiting was effected. The act of expiration was so forcible, that a lighted candle placed near the tracheal orifice was several times extinguished. In a second experiment, a free opening was made into the thorax between the sixth and seventh ribs of the right side. The lung collapsed partially only. During the first efforts to vomit, air was forcibly expelled through this orifice, the lung was brought almost into contact with it, the stomach was not evacuated. But as the efforts to vomit became extreme, a portion of lung was driven through the thoracic opening with violence and a sort of explosion, and at the same instant the stomach yielded its contents. These experiments appear to admit only of one explanation, of one conclusion,-that the act of vomiting is a forcible expiratory effort, the larynx being firmly closed, and the diaphragm perfectly inert.

It must be regarded as singular that M. Bourdon, by whom the action of the expiratory muscles, in their various" efforts," has been so well investigated*, should have adopted other views of the act of vomiting.

Recherches sur le Méchanisme de la Respiration, &c, Par Isid. Bourdon, A Paris, 1820.

It is not intended to state that the act of vomiting is simply such as I have described. There are many facts which appear to show that the oesophagus is not without its share of influence in this act, and it is plain that the cardiac orifice must be freely opened; for mere pressure upon the viscera of the abdomen will not, in ordinary circumstances, evacuate the contents of the stomach. To effect this open state of the cardiac orifice, it is probably necessary that the diaphragm should, indeed, be in a relaxed rather than in a contracted state.

A singular and interesting fact was noticed by M. Majendie, of which he has not given any explanation. During the state of nausea which preceded the act of vomiting, in some of his experiments, air was drawn into the stomach. I am disposed to think that this effect was produced in the following manner the larynx being closed preparatorily to the act of vomiting, an attempt at inspiration is made before the effort of expira tion. In this attempt, air is drawn into the œsophagus, the larynx being impervious, and it is afterwards probably propelled along that canal into the stomach itself. It is not improbable, too, that, in some instances of vomiting, in which the action of the abdominal muscles was subtracted*, a similar effort of inspiration has drawn substances from the stomach into the oesophagus, which has eventually expelled them by an inverted action. Neither of these phenomena could result from any action of the diaphragm, and much less from contraction of the abdominal muscles. But it is easy, by closing the larynx and attempting to inspire, to draw air into the oesophagus. A similar act, if very forcible, might draw a portion of the contents of the stomach through the cardiac orifice.

Such, then, appears to be the nature of the act of vomiting. How different is this act from one in which the diaphragm does, indeed, contract suddenly, under similar circumstances of closure of the larynx,-viz. singultus: the action of the diaphragm being an effort of inspiration, air is apt to be drawn into the oesophagus with considerable noise; and there is occasionally pain, not only about the insertions of the diaphragm, but about the closed larynx.

* Euvres de Legallois, tom ii. p. 105.