MECHANICAL PHENOMENA. 13 



show that it is indeed a reservoir, but a most active one. 

 The changes which the cardiac half of the stomach suffers 

 during an ordinary digestive period is shown in the drawings, 

 which were made by tracing the outlines of the stomach on 

 tissue-paper laid over the abdomen of the cat at various 

 times after feeding. 



By comparing the figures it can be seen that as digestion 

 goes on the antrum seems to elongate and acquire a greater 

 capacity, and that the constrictions make deeper indenta- 

 tions into it (Fig. 2, 11.00-1.30). When the fundus has lost 

 most of its contents the longitudinal and circular fibres of 

 the antrum contract and make it shorter and of less capacity 

 once more. As compared with the changes in the form of 

 the rest of the stomach those in the antrum are slight. 



The first region to decrease markedly in size is the pre- 

 antral part, at the beginning of which the peristaltic waves 

 commence. These gradually force some of the stomach 

 contents in this region into the antrum, so that the pre- 

 antral part little by little begins to assume a tubular form 

 in consequence of the sustained (tonic) contraction of the 

 muscle fibres of this region (Fig. 2, 1.30-2.30). At one 

 end of this tube we have the rounded fundus, rat the other 

 the actively contracting antrum. Shallow constrictions may 

 pass along the tubular portion. 



The muscle fibres (longitudinal, circular, and oblique) found 

 in the fundus gradually contract upon the spherical mass of 

 food found here and slowly force it into the tubular portion. 

 The size of the fundus thus gradually diminishes, until the 

 shadow cast by this portion of the stomach entirely dis- 

 appears (Fig. 2, 5.00-5.30). The tubular portion of the 

 stomach forces j)he food on into the antrum, until finally, 

 when the funcius is empty, the last remnants of food are 

 squeezed out of the tubular portion into the antrum. 



We see from the above that the time which the food spends 

 in the stomach is considerably longer than is commonly 

 supposed. In the illustrations it can be seen that all the 



