CHAP. XXIV.] MOVEMENTS OF THE STOMACH. 195 



ations of the cells or, as we shall term them, pyloric tubes end 

 at length in very short and diminutive true stomach tubes (fig. 156, 

 B) ; but we have likewise found them terminating in either flask- 

 shaped or undilated extremities, lined throughout with the sub-co- 

 lumnar variety of epithelium, (fig. 156, d). Thus, in these animals, 

 a marked distinction exists between the mucous membrane of the 

 pyloric compartment and that of the rest of the organ, a distinction 

 which must undoubtedly have an important physiological meaning : 

 and we have suspected that the digestive power of the two parts 

 must differ; that the office of the pyloric tubes resembles that of the 

 stomach cells generally, and is different from that of the true sto- 

 mach tubes; that perhaps the acid product of the stomach may be 

 furnished by one rather than by the other. We confess, however, 

 that we have been unable, on the one hand, to obtain human sto- 

 machs sufficiently fresh and healthy to test the fact of the anatomi- 

 cal distinctness of the two regions in man, or, on the other, to 

 ascertain the value of the conjectures just alluded to as applied to 

 animals in which the twofold structure is sufficiently certain, 



It is necessary to examine the changes that occur in the stomach 

 upon the introduction of food in it. These changes are threefold : 

 1st, as regards its muscular coat; 2nd, as regards its mucous mem- 

 brane ; and, 3rd, with respect to the nature and properties of the 

 secretion which is derived from that membrane. 



1. Movements of the Stomach. On exposing the stomach of a 

 living animal, or of one recently killed while digestion is going on, 

 we find that it firmly embraces its contents, and that both ori- 

 fices are closed, so as to prevent the escape of the food. This 

 is particularly the case as regards the pyloric orifice in the first 

 period of digestion. The contraction of the circular muscle which 

 surrounds the pylorus is so strong, that, even after the stomach has 

 been separated from the intestines, its contents do not escape for 

 some time. 



This contraction is due to the stimulus of the food ; and, when 

 the aliment is difficult of digestion, the muscular coat is propor- 

 tionably stimulated. 



The movements of the stomach are very different in its cardiac 

 and in its pyloric portions. In the cardiac two-thirds the move- 

 ments are very slow and scarcely perceptible, and seem to consist 

 in little more than a firm and steady contraction upon the contents, 

 the muscular coat thus slowly pushing on the food towards the py- 

 loric portion, and adapting itself to the diminished size of the organ. 

 In the pyloric portion they resemble closely the peristaltic move- 



