204 STOMACH DIGESTION. 



when the fundus has lost most of its contents the longitudinal fibers 

 of the antrum contract to make it shorter and smaller. 



The first region to decrease markedly is the pre-antral part of 

 the pyloric portion. The peristaltic undulations, caused by the 

 circular fibers, start at the beginning of this portion and gradually, 

 by their rhythmic recurrence, push some of the contents into the 

 antrum. As the process continues the smooth muscle-fibers with 

 their remarkable tonicity contract closely about the food that 

 remains, so that the middle region comes to have the shape of a 

 tube (Figs. 110, 111, 1.30 P.M. to 5.30 P.M.), with the rounded 

 fundus at one end and the active antrum at the other. Along 

 the tube very shallow constrictions may be seen following one 

 another to the pylorus. 



At this juncture the longitudinal fibers which cover the fundus 

 like radiating fingers, and the circular and oblique fibers reaching 

 in all directions about this spherical region, begin to contract. 

 Thus the contents of the fundus are squeezed into the tubular 

 portion. This process, accompanied by a slight shortening of the 

 tube, goes on until the shadow cast by the fundus is almost obliter- 

 ated (Fig. Ill, 5.30 P.M.). This shows that the fundus is nearly 

 empty, for there being but little subnitrate of bismuth in it, only 

 a small shadow is cast. 



The waves of constriction moving along the tubular portion 

 force the food onward as fast as they receive it from the contract- 

 ing fundus, and when the fundus is at last emptied they sweep the 

 contents of the tube into the antrum (Fig. Ill, 5 P.M. to 6 P.M.). 

 Here the operation is continued by the deeper constrictions, till 

 finally (in this instance, at 6.12 P.M.), with the exception of a 

 slight trace of food in the fundus, nothing at all is to be seen in 

 the stomach. 



The food in the fundus may possibly be slightly affected by 

 the to-and-fro movements of the diaphragm in respiration. With 

 normal breathing the upper border of the cardiac portion swings 

 through about one centimeter ; with dyspnea, or deep breathing, 

 through one and a half or two centimeters. Since the lower 

 border does not move so much, the contents are gently pressed, 

 and then released from pressure, at each respiration. 



Cannon calls attention to the observation made by Moritz with 

 reference to the value of an organ like the stomach for holding 

 the bulk of the food, and serving it out little at a time so that the 

 intestines may not become congested during their digestive and 

 absorptive processes, and says that all of the advantages supposed 

 to be thus secured" to the intestines may be claimed for the stomach 

 itself. 



The experiments above quoted prove that the stomach is com- 

 posed of two physiologically distinct portions. The busy antrum, 

 over which during digestion constriction-waves are running in 



