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SPECIAL PHYSIOLOGY. 



inal muscles, and with certain peculiar states of the diaphragm and 

 muscles of respiration generally, so producing the acts of eructation, 

 regurgitation, retaking, and vomiting. 



The eructation of gaseous matters depends chiefly on the contrac- 

 tion of the walls of the stomach and oesophagus, aided slightly by that 

 of the abdominal muscles and the diaphragm. 



The act of vomiting is a more general and powerful movement, and 

 often involves a contraction of the small intestines; but it depends 

 essentially on a similar mechanism. Though an exceptional phenome- 

 non, and, in disease, often a serious or fatal symptom, it is, in many 

 instances, beneficial, relieving the stomach of indigestible, irritating, 

 or poisonous substances, expelling from it morbid secretions, or even 

 inducing a state of exhaustion, in some way favorable to ultimate re- 

 covery. Retching is unsuccessful vomiting. 



Regurgitation is performed by the same mechanism as vomiting; but 

 its effect is limited to the expulsion of small portions only of the con- 

 tents of the stomach. There are persons who possess a sort of power 

 of rumination, swallowing their food half chewed, and, after a time, 

 returning it to the mouth, where it is fully masticated, and then re- 

 swallowed. 



The actual contraction of the stomach, in vomiting, is sometimes 

 felt; indeed, it has been witnessed. In a man, in whom the entire 

 stomach protruded through a wound of the abdomen, forcible and re- 

 peated contractions of this organ were observed to continue for half 

 an hour, till it was entirely emptied of its contents (Lepine). As a 

 preliminary condition to the inverted action of the fibres of the stom- 

 ach generally, the pyloric muscular ring contracts tightly, whilst the 

 oblique fibres surrounding the cardiac orifice are always, and neces- 

 sarily, relaxed; otherwise the contents of the stomach could not enter 

 the oesophagus. The ineffectual attempts to vomit, sometimes noticed 

 before the actual expulsion of the contents of the stomach, are due to 

 the contraction of these cardiac fibres, which contraction ordinarily 

 serves to retain the contents of the stomach, during any violent effort 

 on the part of the abdominal muscles. The relaxation of these fibres, 

 in vomiting, is immediately followed by an anti-peristaltic action of 

 those of the oesophagus, movements which have been observed in the 

 horse, after the injection of tartar emetic into its veins, and have been 

 found to continue even when the oesophagus is separated from the 

 stomach. It has been suggested, that the upward propulsion of the 

 contents of the stomach or intestines, and of matters rising in the 

 oesophagus, is due to a downward or peristaltic action meeting with 

 resistance, and producing a central, or so-called axial current upwards 

 (Brinton); but this explanation is not generally adopted, and anti- 

 peristaltic movements certainly occur in animals. 



The influence of the abdominal muscles in vomiting is obvious, and, 

 indeed, Magendie suggested, that these muscles and the diaphragm 

 were alone concerned in this act, the stomach being, as it were, pas- 

 sive, and merely compressed by the descent of the diaphragm, and the 

 backward movement of the abdominal muscles. This view is supported 

 by Beclard and Budge. The administration of tartar emetic, to an 



