?GO 



(ESOPHAGUS. 



liarly called heartburn; and in pyrosis, or water- 

 brash, the amount of liquid which suddenly 

 enters the mouth is often very considerable. 

 This inverted action of the oesophagus admits 

 of a ready explanation. By the contraction 

 of the muscular fibres of the stomach a portion 

 of liquid is expelled into the lower extremity 

 of the oesophagus; here it immediately excites 

 contraction of the muscular fibres which sur- 

 round it, and being prevented from again en- 

 tering the stomach by the momentary continu- 

 ance of the same effort which has expelled it 

 into the oesophagus, it must necessarily pass 

 into the relaxed portion of the tube immedi- 

 ately above; and thus, by the contraction of 

 successive portions of the tube, the liquid soon 

 reaches the pharynx. In ruminants, the greater 

 portion of the food is returned from the sto- 

 mach to the mouth by this inverted action of 

 the oesophagus. During the action of vomiting 

 there is an inverted action of the oesophagus in 

 addition to the propulsive effort arising from 

 the contraction of the stomach and abdominal 

 muscles. 



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 stimulus 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 oeso- 

 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 frM>d along the 

 oesophagus 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 oesophagus, 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 health. 

 An apparent exception to the general rule that 

 the movements of the oesophagus 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 

 oesophagus, however, appears by no means neces- 

 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 oesophagus, 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 stomach, 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 oesophagus 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 cesophageal 

 plexus, but below the pharyngeal branches. 

 The animal received the food which was offered 

 to it, and by a propulsive effort of the tongue 

 and pharynx transmitted it to the oesophagus, 

 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 oesophagus 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 oesophagus, there 

 remains butoneexplanation of these movements, 

 which is, that they belong to the class of reflex 

 actions. An impression made upon the mucous 

 membrane of the oesophagus is communicated 

 by the afferent nerves to the medulla oblon- 

 gata, 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. 

 The only parts of this circle of actions which 

 we recognise by our senses are the application 

 of the stimulus and the occurrence of the mus- 

 cular contraction ; but these are doubtless con- 

 nected in the manner above mentioned. The 

 oesophagus receives both its excitor and its 

 motor nerves from the pneumo-gastric ; it thus 

 derives its nervous influence from that portion 

 of the nervous centre, namely, the medulla 

 oblongata, which is the centre of the respiratory 

 movements. Hence it will be seen that when 

 in any case of disease of the nervous centres 

 deglutition becomes seriously impaired, there is 

 much reason to fear that the moreimportantfunc- 

 tion of respiration will soon become involved. 



Abnormal anatomy. The oesophagus may de- 

 viate from the normal state in form or in struc- 

 ture. In some cases malformation may exist 

 without obvious change of structure, but it is 

 more common to find them combined. Mal- 

 formation of the oesophagus may be either con- 

 genital or acquired. 



Congenital malformation. It sometimes 

 happens that the oesophagus is congenitally 

 deficient, terminating above in a cul-de-sac, 

 the inferior extremity of the pharynx also ter- 

 minating in the same manner. This is usually 

 associated with an imperfect developement of 

 the oral cavity and of the lower jaw, the latter 



* Sec the Edin. Med. and Surg. Journal. 



