STOMACH AND INTESTINE. 



313 



mucous membrane gently close upon it, and 

 gradually diffuse it over the whole surface.* 



c. The ordinary state of the human stomach 

 during the diges'tive act lies between these 

 two extremes; and may be defined as one of 

 moderate distention, with food which has 

 been subdivided by mastication, and diluted 

 with saliva and gastric juice, so as to possess 

 a pulpy or semi-fluid consistence. 



In attempting to imitate this condition in 

 the Dog, I have found it best to choose an 

 aliment which already possesses a pultaceous 

 or semi-liquid consistence, such as a thick 

 soup, and to administer it in large, but not 

 excessive quantity. On pithing the animal a 

 quarter of an hour afterwards, the following 

 movements are seen. The most noticeable 

 is a peristalsis or transverse constriction, which 

 sets out from the cardiac extremity, and tra- 

 vels slowly towards the pylorus. It is com- 

 paratively feeble until it reaches the junction 

 of the pyloric two-fifths, and the cardiac three- 

 fifths of the organ. Here it suddenly becomes 

 much more distinct ; and from hence continues 

 rapidly forwards, as a well-marked circular 

 depression, until it reaches the pylorus. Hav- 

 ing arrived there, an interval of relaxation suc- 

 ceeds, and is followed by the recurrence of 

 a similar contraction. As nearly as can be 

 judged, the average period of relaxation is 

 about one minute, and the contraction itself 

 occupies nearly the same time. Cotempora- 

 neous with this contraction there is a cer- 

 tain amount of longitudinal shortening of 

 the organ. The pyloric orifice is always 

 firmly shut. 



In the interior of the human stomach, Dr. 

 Beaumont could only verify an alternate con- 

 traction and relaxation ; a vermicular action 

 of the transverse fibres, and a shortening pro- 

 duced by the longitudinal coat. The exact 

 details of this occurrence he could not follow. 

 He also noticed a constant agitation of the 

 organ produced by the respiratory muscles.f 

 But Dr. Todd and Mr. Bowman J have men- 

 tioned a case, in which the vermicular actions 

 of a distended stomach were distinctly seen 

 through the wall of the belly during life. 



So far as this imperfect evidence goes, it is 

 evidently favourable to the view, that the 

 muscular contraction of the human stomach 

 during this stage of digestion is similar to that 

 seen in the newly-killed animal. 



It is therefore our next object to inquire 

 (1) What are the movements which such a 

 peristalsis would necessarily impress upon the 

 food ? And (2) how far do they correspond 

 with those which have been actually ob- 

 served ? 



(1.) The effect of peristalsis in a closed and 



* Condensed, in Dr. Beaumont's own words, 

 from pp. 62, 63. 96, 97, of his work. This activity 

 of the rugae themselves may remind us of their 

 inherent muscularity (see p. 325. of this article). 



f Probably much exaggerated, if not chiefly pro- 

 duced, by the adhesion of St. Martin's stomach to 

 the wall of his chest. 



J Todd and Bowman's Physiological Anatomy, 

 vol. ii. p. 196. 



distended tube may be represented by an in- 

 flexible hollow cylinder, filled with liquid, and 

 accurately fitted with a perforated septum (6, 

 fig. 244.), which is capable of free movement 

 along its interior. Let such a septum be moved 

 in either direction, and it at once exerts a pres- 

 sure on the body of liquid (c) contained in that 

 end (a) towards which its motion sets. The 

 pressure being equal in all directions, a portion 

 of the fluid escapes backwards through its 

 aperture (</). This retrograde course is, 

 pro tanto, a current ; and one which will 

 be continually lengthened by the advance of 

 the septum along the remainder of the 

 tube. And the slow successive movement of a 

 series of such septa would establish two con- 

 tinuous currents in the liquid ; a peripheral of 

 advance, and a central of return.* 



Fig. 244. 



Diagram to illustrate the effects of peristalsis in a 

 closed tube containing liquid. 



a, Closed end of the tube ; b, perforated septum, 

 moved towards a, and causing the peripheral cur- 

 rents indicated by the arrows, in the same direction ; 

 c, quiescent mass of liquid, giving origin to d; rf, 

 central current, prolonged from the corresponding 

 arrow, and passing through the perforated septum. 



The existence of two such currents would 

 be little affected by the membranous nature 

 or peculiar shape of the human stomach. 

 Even comparative inactivity of the cardiac 

 pouch would not prevent their occurrence, as a 

 consequence of pyloric peristalsis. While very 

 moderate contractions of this sluggish part 

 would accurately define the axis and its cur- 



* The following description so well supplies the 

 interval between such a model tube and the human 

 stomach, that I cannot refrain from quoting it. 

 " The muscular action of a fish's stomach consists of 

 vermicular contractions, creeping slowly in continu- 

 ous succession from the cardia to the pylorus, and 

 impressing a twofold gyratory motion on the con- 

 tents ; so that, while some portions are proceeding 

 to the pylorus, others are returning towards the 

 cardia." (Owen's Hunterian Lectures, vol. ii. p. 236.). 



