STOMACH AND INTESTINE. 



319 



instances of the second, we might adduce, not 

 only that ordinary form of vomiting which is 

 brought about by a direct irritation of the 

 stomach itself, but those numerous cases in 

 which it follows the application of various 

 stimuli to similar or different parts. Such are 

 mechanical irritations of the soft palate, intes- 

 tines, or peritoneum ; disgusting smells, sights, 

 or sounds ; prolonged immersion in cold water; 

 or even wounds of the extremities. 



The path by which these several kinds of 

 peripheral irritation reach the nervous centre 

 probably varies in different cases. Where they 

 are mechanical, it is obvious that they are con- 

 ducted to the central organ by the afferent or 

 sensitive nerves upon which they impinge. 

 Thus, as regards the stomach itself, irritation 

 or section of the pneumogastric or splanchnic 

 nerve often produces vomiting. But some 

 emetic substances, such as antimony*, are 

 equally active when introduced into the blood. 

 And Magendie's experiment f shows that 

 whether the poisoned current of this fluid ge- 

 nerally exerts a local action upon the stomach 

 or not it is to its influence upon the ner- 

 vous centres that the act of vomiting must 

 mainly be referred. The various constituent 

 phenomena of the process sufficiently indicate 

 the medulla oblongata as that segment of the 

 cerebro-spinal centre in which the reflection 

 towards the periphery occurs. But the en- 

 suing movement is by no means a simple reflex 

 action. On the contrary, the number of 

 organs linked together to produce it, and the 

 alteration in their ordinary times, modes, and 

 degrees of activity which they exhibit, render 

 the whole process so complex, so truly co- 

 ordinate, that, far from limiting* our attention 

 to the mere reflex course which its exciting 

 cause sometimes takes, we ought rather to 

 regard vomiting as an involuntary or physical 

 nervous action of the highest order. The 

 sensations that have been noticed as accom- 

 panying it seem probably due to the cogni- 

 zance taken by different organs, of changes 

 which are perhaps themselves motor. At 

 any rate, we are hardly justified in classify- 

 ing them along with the " reflex sensations " 

 sometimes met with in disease. 



In some instances, a curious variety of the 

 process of vomiting seems to return different 



purely mental emotion, and which is typified in the 

 exaggerated phrase of " being sick " of any thing or 

 topic. 



* With respect to the vomiting produced by tar- 

 tar-emetic, the author has made an observation 

 which tends to ahow that, whatever the mechanical 

 share taken by the stomach itself in the act, this 

 organ does, in some instances, effect such a local 

 secretion of the emetic from the blood into the 

 gastric cavity, as may tend to remove the drug from 

 the system. On injecting a solution of tartar-emetic 

 into the superficial femoral vein of a dog, the mi- 

 neral was found ten minutes afterwards in the fluid 

 contents of the animal's (digesting) stomach, in a 

 state of concentration much exceeding that in which 

 it must have been mixed with the mass of the blood. 

 And there seem to be reasons for conjecturing that 

 a similar local secretion occurs in the case of the salts 

 of some other metals ; and, probably, of ipecacuan. 



f Quoted at p. 317. 



parts of the gastric contents at different inter- 

 vals of time ; the expulsion of more fluid 

 and digested portions being followed, after 

 the lapse of a considerable period, by that of 

 crude and undigested masses of food. A small 

 number of such cases perhaps depend on a 

 peculiar hour-glass shape of the organ, aided 

 by a casual constriction due to its muscular 

 coat: conditions which might unite to iso- 

 late a part of the contents of the organ for a 

 longer or shorter period. But most of them 

 might probably be explained by the weight, 

 bulk, and situation of the alimentary masses 

 in the organ ; and by the other mechanical 

 circumstances which favour or impede the act 

 of vomiting itself. 



The last efforts of a prolonged vomiting 

 often bring up a quantity of bile. But from 

 what has already been stated, it is evident, 

 that during the intervals of energetic vo- 

 miting, a portion of the duodenal contents 

 may easily find their way into the stomach, 

 and be subsequently expelled thence. In- 

 deed, it may be doubted whether the pylorus 

 is completely occluded at the moment of the 

 expulsive act : especially in those cases in 

 which the intestines are themselves distended 

 with fluids exposed to the same violent pres- 

 sure as the contents of the gastric cavity. 



Rumination. There are certain individuals 

 who are capable of returning, at will, a greater 

 or smaller portion of the contents of the di- 

 gesting stomach into the cavity of the mouth. 

 This act has received the name of rumination, 

 from its analogy to the ruminant process 

 which forms a stage in the normal digestion 

 of some animals. Like the latter, it is a vo- 

 luntary return of the undigested food, which 

 is often followed by a re-mastication of its 

 more solid portions. Apart from its voluntary 

 character, it might be regarded in either of 

 two points of view : as a more complete form 

 of regurgitation ; or as a peculiar variety of 

 vomiting, akin to that seen in infants, and, like 

 it, especially distinguished by the absence of 

 nausea and of constitutional disturbance. 



The mechanism of the process appears to 

 be precisely what these analogies would imply. 



A very deep inspiration is followed by a vo- 

 luntary contraction of the abdominal muscles ; 

 and, after a moment during which the trunk 

 is kept motionless, the food rises into the 

 mouth.* From hence, after more or less mas- 

 tication, it is again swallowed in the ordinary 

 way. The abdominal contraction sometimes 

 requires to be aided by manual pressure in 

 the gastric region. The date and duration 

 of the act, as well as the frequency with 

 which it is repeated, vary greatly in different 

 cases. 



The precise share taken by the stomach 

 itself in this rumination seems just as ob- 

 scure and is probably as variable as that 

 by which it assists in the act of vomiting. 



In many instances an examination of the 

 organ after death has shown no peculiarity of 



* Magendie's Physiologic, tome ii. p. 152. 



