MOVEMENTS OF THE STOMACH. 407 



430. With regard to the degree in which these movements of the Stomach, 

 whose share in the Digestive operation is so important, are dependent upon the 

 Spinal cord, and are consequently of a "reflex" nature, it is difficult to speak 

 with certainty, owing to the contradictory results obtained by different experi- 

 menters. These contradictions, however, seem partly due to a diversity in the 

 nature of the animals experimented on, and partly to a difference in the stage 

 of the digestive process at which the observations were made. It seems to be well 

 established, by the researches of Reid, Valentin, and others, 1 that distinct 

 movements may be excited in the Stomach of the Rabbit, if distended with food, 

 by irritating the Pneumogastric soon after the death of the animal ; these move- 

 ments seem to commence from the cardiac orifice, and then to spread themselves 

 in a sort of peristaltic manner along the walls of the stomach ; but no such 

 movements can be excited if the stomach be empty. Various experiments upon 

 living animals have led to a similar conclusion ; food taken in shortly before or 

 subsequently to its division, having been found to be only dissolved on the sur- 

 face of the mass, where it was in contact with the mucous membrane. But these 

 experiments have been made for the most part upon Herbivorous animals, such 

 as horses, asses, and rabbits ; whose food is bulky and difficult of solution, re- 

 quiring to be constantly changed in its position, so that every part of it may be 

 successively brought to the exterior. On the other hand, Dr. Reid found, in 

 his experiments upon Dogs, that, after the first shock of the operation had gone 

 off, solution of food in the stomach, and absorption of chyle, might take place; 

 and hence it may be inferred, that no influence of this nerve upon the muscular 

 parietes of the stomach is essential to digestion in that species. This conclusion 

 harmonizes well, therefore, with the fact already stated respecting the absence 

 of such influence in the lower parts of its 03sophagus ; and it may, perhaps, be 

 explained by the consideration, that the natural food of the dog is much less 

 bulky and more easy of solution than that of the animals already named j so 

 that there is not so much need of that peculiar movement, which is in them so 

 important an aid to the process of reduction. There is yet much to be learned 

 on this subject, however; especially in regard to the degree in which the move- 

 ments may be checked or altered, by impressions transmitted through the nerv- 

 ous system. It was stated by Brachet, that, in some of his experiments upon 

 the Pneumogastric, some hours after section of the nerve on both sides, the sur- 

 face only of the alimentary mass was found to have undergone 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 plea- 

 surable emotions may be favorable to the operation \ not only by giving firmness 

 and regularity to the action of the heart, and thence promoting the circulation 

 of the blood, and the increase of the gastric secretion ; but also in imparting 

 firmness and regularity to the muscular contractions of the stomach. 



431. Much discussion has taken place upon the question, how far contraction 

 of the parietes of the Stomach itself actively participates in the operation of 

 Vomiting- and many experiments have been made to determine the facts of the 

 case. Some, as Magendie, have gone so far as to affirm that the stomach is 

 entirely passive ; grounding this inference upon the fact experimentally ascer- 

 tained, that when the stomach was removed, and a bladder was substituted for 



1 See Dr. Reid's "Physiological, Anatomical, and Pathological Researches," chap. v. ; 

 Valentin "De Functionibus Nervorum Cerebralium," &c., chap. xi. ; also Longet, "Anatomic 

 et Physiologic du Systeme Nerveux," torn. i. p. 323 ; and Bischoff, in "Mviller's Archiv.," 

 1843. 



