THE DIGESTIVE SYSTEM. 253 



ciently large portion is cut off from the rest by contrac- 

 tion of the sphincter^ and thus the pellet to be returned 

 to the mouth is formed. Reversed peristalsis commences 

 against the omasum at that part of the canal which is 

 occupied by fluid material from the reticulum. Some of 

 this is forced into the omasum during the contraction of 

 the canal. The action of the rumino-reticular sphincter 

 is similar in nature, but reverse in its action to that of 

 the pylorus ; the latter guards against passage of solid 

 masses, the former sometimes contracts to guard against 

 liquids, as probably during drinking. Sufficiently elabo- 

 rated food passes directly into the omasum, and here is 

 subjected to compression. The laminae are so arranged 

 that matter can pass in between them and lie there, being 

 gradually moved outwards towards the abomasum ; but 

 the arrangement of their muscular structure is such that 

 when the stomach contracts they also diminish in length, 

 and thus do not block up the channel at the lesser curva- 

 ture of the viscus, along which, as through part of the 

 oesophagus, a passage generally is open for liquids or very 

 pultaceous material. The anatomical arrangement of the 

 oesophageal canal shows no reason why, if peristalsis is 

 regular (not reversed), the soft material from the reti- 

 culum should not pass into the omasum. Probably a 

 handing on of prepared matter thus takes place. The 

 omasum seems rather a means of sustaining the groove 

 during rumination, and a protector of the abomasum from 

 the influx of coarse food particles, than a reservoir in 

 which any important quantity of the food is stored up for 

 a time. These deductions from anatomical facts are con- 

 firmed by several experiments by Flour ens on living 

 animals. Other theories of rumination are : 



I. That food handed from the rumen into the reticulum 

 is by it moulded into a pellet and handed into the oeso- 

 phagus, and that when it again descends it is soft, and, 

 therefore, enters the omasum, for it passes over the 

 floor of the groove without separating the pillars 

 (Dauberton) . 



II. That the food for remastication is driven into the 



