500 OF FOOD, AND THE DIGESTIVE PROCESS. 



[Fig. 203. 



A view of the interior of the Stomach and Duodenum in situ, the inferior portion of each having been 

 removed; 1, 1, the under side of the liver; 2, the gall bladder; 3. 3, the lesser curvature and anterior 

 faces, as seen from below ; 4, the rugte, about the cardiac orifice; 5, the pyloric orifice ; 6, the ruga;, and 

 thickness of this orifice ; 7, 7, the duodenum; S, lower end of the right kidney.] 



into the great curvature, to perform similar revolutions. These revolutions 

 are completed in from one to three minutes. They are probably induced in 

 a great measure, by the circular or transverse muscles of the stomach. They 

 are slower at first, than after chymification has considerably advanced ;" at 

 which time also there is an increased impulse towards the pylorus. It is 

 probable that, from the very commencement of chymification, until the organ 

 becomes empty, portions of chyme are continually passing into the duode- 

 num ; for the bulk of the alimentary mass progressively diminishes, and this 

 the more rapidly as the process is nearer its completion. The accelerated 

 expulsion appears to be effected by a peculiar action of the transverse mus- 

 cles ; and especially of that portion of them which surrounds the stomach at 

 about four inches from its pyloric extremity. This band is so forcibly con- 

 tracted in the latter part of the digestive process, that it almost separates the 

 two portions of the stomach, into a sort of hour-glass form ; and Dr. B. states 

 that, when he attempted to introduce a long thermometer tube into the pyloric 

 portion of the stomach, the bulb was at first gently resisted, then allowed to 

 pass, and then grasped by the muscular parietes beyond, so as to be drawn 

 in: whence it is evident that the contraction has for its object, to resist the 

 passage of solid bodies into the pyloric extremity of the stomach, at this stage 

 of digestion ; whilst the matter which has been reduced to the fluid form is 

 pumped away (as it were) by the action of that portion of the viscus. These 

 peculiar motions continue, until the stomach is perfectly empty, and not a par- 

 ticle of food or chyme remains. Of the degree in which they are dependent 

 upon the influence of the Nervous System, some idea has been already given 

 ( 387) ; there is yet much to be learned, however, especially in regard to the 

 degree in which the movements may be checked or altered, by impressions 

 transmitted through the nervous system. It is stated by Brachetthat, in some 

 of his experiments upon the Par Vagum some hours after section of the nerve 

 on both sides, the surface only of the alimentary mass was found to have un- 

 dergone solution, the remainder of the mass remaining in the condition in 

 which it was at first ingested ; and if this statement can be relied on, it would 

 appear that the movements of the stomach, like those of the heart, can be 

 readily affected by a strong nervous impression. It may be partly in this 

 manner, therefore, and not by acting upon the secretions alone, that strong 

 Emotions influence the digestive process, as they are well known to do. On 

 the other hand, the moderate excitement of pleasurable emotions may be fa- 



