We have now to point out the precise mode in which these contractions are induced, to explain the intermediate links between the ap plication of a stimillus to the mucous mem brane and the occurrence of the muscular con traction. In the first place, unless we swallow a very large or • a very hot morsel of food, no sensation attends its passage along the (eso phagus. After the food has passed that portion of the pharynx upon which the glosso-pha ryngeal nerve is distributed, we cease to be con scious of its presence; and again, when a bitter liquid is eructated from the stomach, it pro duces no sensation of taste until it reaches the same point. As the passage of food along the cesophagus is unattended by sensation, so is it uninfluenced by volition. We cannot by any effort of the will perform the action of deglu tition unless we bring a portion of food, or a liquid (as the saliva), into contact with the pha rynx, by means of which the action of the parts may be excited. Again, no effort of the will can arrest the process of deglutition after the food has entered the cesophagus, and if a liquid be made to pass into the pharynx of a person in whom the exercise of volition is suspended by a fit of apoplexy, deglutition is performed in a manner almost as perfect as by a person in heal th. An apparent exception to the general rule that 'the movements of the cesophagus are beyond the control of the will is afforded by the very rare examples of persons possessing the power of rumination. A voluntary power over the cesophagus,however, appears by no means neceg sary to account for this. It probably depends on the possession of an unusual degree of vo luntary power over the movements of the sto mach, and especially of its cardiac orifice, by means of which the contents of the stomach can be expelled at will into the inferior extre mity of the cesophag-us, and thus are brought within the influence of its involuntary move ments. Any one may satisfy himself that he possesses some degree of voluntary power over the cardiac orifice of the stoinaeli, if after swallowing a bottle of soda water he will direct attention to the power which he pos sesses of preventing the sudden escape of gas from the stomach, and, on the contrary, of increasing the propulsive effort probably by contracting the abdominal muscles. It is pro bable that many persons might by practice acquire the power of rumination. Since the contractions of the cesophagus cannot be ex cited by volition, are they dependent on the direct stimulus of the muscular fibres by con tact of the food, independently of the nerves and of the nervous centres? That this is not the case is proved by an experiment performed by Dr. J. Reid.. He divided in a rabbit the vagus nerve on each side above the cesopliageal plexus, but below the pharyngeal branches. fhe animal received the food which was offered to it, and by a propulsive effort of the tongue and pharynx transmitted it to the (esophagus, which, having lost all power of contraction, remained passive, and became at length com pletely distended and choked up by the mate rials thrust into it from above. It is evident then that the (esophagus loses its power of contraction if we cut off its communication with the nervous centres. As we have before seen that the will is not the agent which deter mines the contractions of the (esophagus, there remains butoneexplanation of these movements, which is, that they belong to the class of reflex actions. An impression made upon the mucous meinbrane of the cesophagus is communicated by the afferent nerves to the medulla oblon g-ata, and thence an influence, the precise na ture of which we are ignorant of, is reflected . along the efferent nerves to the muscular fibres of the part to which the stimulus was applied.i The only parts of this circle of actions whiclt we recognise by our senses are the application I of the stimulus and the occurrence of the mus cular contraction; but these are doubtless con nected in the manner above mentioned. T cesophagus receives both its excitor and i motor nerves from the pneumo-gastric ; it th derives its nervous influence from that porti of the nervous centre, namely, the medul oblongata, which is the centre of the respira movements. Hence it will be seen that in any case of disease of the nervous deglutition becomes seriously impaired, t much reason to fear that the more important tion of respiration will soon become involve Abnormal anatomy.—The (esophagus may d viate from the normal state in form or in stru ture. In some cases malformation may exi without obvious change of structure, but it more common to find them combined.
formation of the cesophagus may be eith genital or acquired.
Congenital malformation.— It sont happens that the (esophagus is conge deficient, terminating above in a cul-d the inferior extremity of the pharynx also t rninating in the same manner. This is usual associated with an imperfect developement the oral cavity and of the lower jaw, the latt being in great part or altogether deficient. In some cases the pharynx does not terminate in a cul-de-sac, but opens by a small orifice at the side of the neck. Another corigenital mal
formation more rare than the last consists in the division of a poition of the cesophagus into two canals placed side by side.
Acquired maljbrination.—One of the most common kinds of acquired malformation is dilatation either general or partial. In the Museum of King's College there is a remark able specimen of a dilated cesophagus. At each extremity it is healthy and of the natural size; the intermediate part is enlarged to an extra ordinary degree of dilatation ; the lining mern brane is thickened and opaque, and has the appearance of having partially yielded from dilatation. The muscular fibres were of the natural colour arid thickness. The dysphagia in this case vvas as great as in a case of stric ture.4` Dilatation is a common consequence of stricture. In such cases the dilatation usually occupies the vvhole circumference of the canal. In some rare cases dilatation occurs in the form of a pouch projecting on one side of the canal. Occasionally the mucous mem brane alone becomes pouched, protruding as a hernia between the muscular fibres, but more commonly the muscular coat also dilates and expands over the pouch. Bleuland mentions a case in which a large pouch containing ali mentary matters compressed the canal below so as completely to close it, and to prevent the passage of food into the stomach. These pouches are most common at the upper ex tremity of the cesophagus, probably in ,con sequence of the sudden constriction which the canal undergoes at this point, and partly too in consequence of the muscular coat being thinner 1 here than in any other part.t I Structural changes.—Arnong the most com mon are those which result from inflam II mation, which however is seldom idiopathic, but generally the consequence of swallowing irritating substances, hot liquids, the strong acids or alkalies. The effects in such cases vary in degree from slight redness and soften ing of the mucous membrane, to ulceration and sloughing of the-Whole circumference of the tube. The Museum at King's College con tains a preparation of an cesophagus and of a slough discharged from it, which was taken from ayoung -woman who had swallowed oil of vitriol. A week afterwards she brought up a slough having a tubular form, and consisting of the whole lining membrane of the gullet. Some 1 i of the muscular fibres were plainly visible on I the outside of the slough, in its recent state.t 1 Dr. Baillie gives a drawing of a Also mem brane lining the pharynx and cesopliagus, taken 'from a patient who had thrush.
I The cesophagus is very frequently the seat of stricture, the causes of which are various. Not unfrequently it depends on the contraction of ki cicatrix after sloughing produced by the con tact of some irritating agent. The constriction in these cases appears to go on continually in creasing. Sir C. Bell mentiorra a case in which starvation was the consequence of stricture of the cesopliagus, twenty years after swallowing a quantity of soap lees. Another common cause of stricture is cancerous disease. This is generally confined to the lower extremity, but occasionally it pervades every part of the cesophagus, A more rare case of stricture is described by Sir E. Home t In this case a membrunouspartition extended across the canal; in the centre of the partition was a narrow passage; the coats of the esophagus surround ing the stricture were but slightly changed. In cases of simple imflammatory stricture all the coats of the cesophagus are thickened and indurated at the seat of stricture, lymph is effused between them, and the bloodvessels are enlarged and distended. In consequence of stricture the cesophagus above becomes much dilated; sometimes ulceration and abscess occur. Dr. Monro mentions a case in which death occurred suddenly in' consequence of purulent matter escaping into the trachea.
Morbid growths are occasionally found in the cesophagus. Dr. Monrot describes the dissection of a man aged 68, in whom the cesophagus was dilated by a large fleshy excre scence or polypus. It was attached three inches below the epiglottis and reached down to the upper orifice of the stomach. Haller§ gives an account of the dissection of a man, in whom was found a polypus about seven fingers' breadth long, and of the thickness of a 'worm, which in its general appearance it very much resembled ; it had a carneo-fibrous appearance, a soft consistence, and a deep red colour. Fatty and steatomatous tumours have occasionally been found in the gullet. In other cases a portion of the canal has been found converted into bone, or cartilaginous tumours have grown from.it.
An aneurism springing from the posterior part of the arch of the aorta may compress the cesophagus against the spine. The imme diate consequence is difficulty of swallowing and other symptoms of stiicture, and at length in many cases ulceration and sloughing of the esophagus with escape of blood from the aneu rism either into the mouth or the stomach.