316 



STOMACH AND INTESTINE. 



the obstructed canal, fseces pass through it 

 from the duodenum with equal facility, al- 

 though the stomach soon resents their pre- 

 sence by vomiting ; an act which seems 

 generally to imply a shut pylorus. And 

 Magendie* has observed, that the gases of 

 this upper portion of the intestine can be 

 made to pass the valve with equal facility ; 

 while those distending the stomach excite its 

 contraction. 



Under ordinary circumstances, whatever 

 be the period during which the contents of 

 the stomach sojourn in its cavity, or the 

 movements they experience at this time, they 

 are finally propelled onwards into the duo- 

 denum. 



Sometimes, however, they take a backward 

 course ; and pass through the ossophagus, to 

 re-enter the mouth, and be expelled from this 

 cavity. Such a reversal of their normal 

 direction occurs in the acts of eructation, 

 regurgitation, and vomiting. These acts, 

 however they may differ in their details, must 

 ( priori) agree in the conditions of their oc- 

 currence. They require a relaxation of _the 

 cardia, a closure f of the pylorus, and a com- 

 pression of the stomach. The latter of these 

 three requirements may either be the result 

 of the contractions of the organ itself, or may 

 be effected by an external or independent 

 pressure. 



In simple eructation or belching, part of 

 the gaseous contents of the stomach are 

 ejected from the mouth. This act generally 

 occurs towards the close of digestion, and in 

 dyspeptic individuals ; the quantities of gas 

 thus evolved being often very considerable. 

 In what way the cardia is opened, or how far 

 the evolution of large quantities of these aeri- 

 form fluids in the stomach may not contribute 

 to render it patulous, is at present very doubt- 

 ful. But the intermittent character of the 

 occurrence certainly looks unlike a mere leak- 

 age of an aeriform fluid. While the frequency 

 with which the human stomach contains gases, 

 and the completeness with which the cardia 

 resists their expulsion in vivisected animalsj, 

 increase the difficulty of such a supposition, 

 and, so far, tend to confirm that of a tem- 

 porary relaxation of this aperture. The di- 

 rect agent of the expulsive act seems equally 

 uncertain. The contractions of the stomach 

 seem quite sufficient to account for it. And 

 there is certainly no violent abdominal pres- 

 sure. But such mobile fluids would scarce 

 require a remarkable effort. While, as far as 

 can be judged, the act appears to coincide with 

 the period of expiration. 



An examination of that voluntary eructa- 

 tion which most persons can accomplish, may 

 perhaps strengthen the conjecture, that some 



* Op. cit. p. 83. 



f Of course this closure need only be comparative : 

 that is, the mere resistance of the contents of the 

 stomach to compression would suffice to determine 

 their passage through the more relaxed of its two 

 orifices. 



J As in Magendie's observations, elsewhere al- 

 luded to. 



slight abdominal pressure is a constituent of 

 the ordinary act. Here, by a kind of twitch- 

 ing* action of the oesophagus, which is ac- 

 companied by a sensation that is referred to 

 the upper portion of this tube, air is intro- 

 duced into its interior; and is then expelled, 

 with a considerable sound, by a well-marked 

 movement of expiration, during which the 

 glottis appears to be at least partially closed. 

 And the expulsion of the air artificially intro- 

 duced is often accompanied by that of a por- 

 tion which was previously contained in the 

 stomach itself. So that involuntary and vo- 

 luntary eructation may be said to merge into 

 each other.f 



In the act of regurgitation, more or less of 

 the liquid contents of the stomach are returned 

 into the mouth. This act closely resembles the 

 preceding, of which it often appears to be an 

 accidental complication ; a small portion of 

 liquid being carried *upwards, along with an 

 eructation of gas. In other instances, how- 

 ever, the liquid is unaccompanied by elastic 

 fluid ; and rises so quietly, that it is only per- 

 ceived on reaching the fauces and back of the 

 tongue, where its acid taste causes it to be at 

 once recognized. It is probable that the pro- 

 cess which effects this expulsion is similar to 

 that of eructation. If we could conjecture 

 any difference, it would be, that the abdominal 

 pressure plays a less important part. 



The act of vomiting differs from both of 

 the preceding : not only in the miscellaneous 

 character of the matters which it can expel 

 from the stomach, and in the greater energy 

 with which it is effected ; but also in the fact, 

 that a pressure extrinsic to the organ itself 

 here forms what is, at any rate, the chief agent 

 of the process. 



This abdominal pressure, which has been 

 before alluded to, we shall now proceed to 

 describe. 



In those ordinary movements of respiration 

 which are executed chiefly by the diaphragm 

 and abdominal muscles, the bulk or capacity 

 of the belly is little affected. For during the 

 act of inspiration, the descent or contraction 

 of the former, exactly coincides with the relax- 

 ation of the latter muscular structures ; while 

 during that of expiration, the compression 

 which these exercise is neutralized by the re- 

 cession or ascent of the now relaxed dia- 

 phragm. Hence the moveable viscera of the 

 belly themselves evade all pressure; and 

 merely transfer a very slight force from the 

 anterior to the upper wall of the cavity, or 

 vice versa. But if, while the diaphragm re- 

 mains depressed and contracted, the abdo- 



* This is often called a deglutition of air, although 

 the movement is utterly unlike that of swallowing. 



f Thus the dyspeptic poor who crowd the out- 

 patient rooms of hospitals, sometimes eructate so 

 voluntarily, and even ostentatiously, that the act 

 really seems to be done, not so much to expel gas 

 from an over-distended stomach as to attract com- 

 miseration. And it is said that, in polite Chinese 

 circles, a chorus of eructations at the end of a 

 banquet formally acquaints the host with the re- 

 pletion of his grateful guests. 



