0BSERVATr01S[S ON POLYZOA. 147 



The food is gathered iu the funnel-shaped part of the 

 oesophagus until the increase in bulk enables the transverse 

 muscular fibre of the third meml^rane to act. It is thence 

 carried rapidly into the stomach by a peristaltic motion 

 of the walls, the dividing valve opening for its admis- 

 sion. 



The peristaltic motions still continuing push it to the 

 fundus of the coecum, and then passing over it reverse the di- 

 rection of the motions, sweeping the whole mass back again 

 to the oesophagal valve. Thus the food is alternately 

 rolled from one end of the stomach to the other, or, rather, 

 from what may be homologically designated the centre of 

 the anterior side to the oesophagal end. Occasionally when 

 transported with extraordinary violence against the upper 

 barrier the valve gives way, becoming inverted, and the 

 food pours into the oesophagus. It never, however, reaches 

 the mouth, being invariably and almost instantly restored 

 to the stomach. 



The momentary pause of the annular wave at the an- 

 terior end of the huge coecum and the fading out of the 

 longitudinal rugas and deep brown color of the internal 

 layer in this part, induced Prof. Allman to describe it as 

 differing in structure and function from the rest of the 

 stomach. The fundus of the coecum, however, resembles 

 in these features, except in so far as they are modified to 

 accord with its rounded surface, the intestinal and oesoph- 

 agal extremities. The pause of the " hour-glass constric- 

 tion," momentarily separating this region of the cavity, is 

 consequent upon the large size of the cavity, and the peri- 

 staltic motions of the walls. These following up the food 

 jam it against the bottom and cause a globular distension, 

 which the contractile energy of the muscles cannot over- 

 come until the diameter of the swelling is lessened ; and 

 while this is being effected by the forced return of part 

 of the contents through the neck of the hour-glass, the 

 anterior motion of the wave is necessarily arrested 

 and a delusive aspect of permanence given to the constric- 

 tion, which it does not really possess. Similar globular 

 distensions do not characterize the posterior region of the 

 stomach, because of the smaller diameter of that part, and 



