194 A MANUAL OF VETERINARY PHYSIOLOGY 



Stomach Digestion in Ruminants. 



The Rumen is divided into four sacs, by the constrictions 

 produced in its wall by large muscular bands, which on the in- 

 terior of the organ are of immense thickness, and well deserve 

 the name of pillars. The interior of the organ is lined with a 

 well-developed mucous membrane, covered with pointed papillae, 

 3 to 9 mm. in length, excepting where the muscular pillars are 

 most prominent. A few small glands are described as existing 

 in this mucous membrane, but they form no digestive secretion. 

 The rumen communicates freely with the reticulum ; by means 

 of the oesophageal groove it is connected with the omasum, and 

 it naturally connects with the oesophagus. Material in the 

 rumen can do one of three things — either pass into the reticulum, 

 into the omasum, or into the oesophagus. The way to the 

 omasum is via the oesophageal groove. 



The (Esophageal Groove or gutter is a canal with an incomplete 

 wall, which runs from the entrance of the oesophagus to the 

 omasum. On its way it has growing from it two diverticula 

 with which it. communicates — viz., the rumen and reticulum — 

 and it is in order to connect it with these that the wall of the canal 

 is incomplete. This groove from the oesophagus to the omasum 

 runs on the inner wall of the reticulum, but at no time is the 

 interior of the canal itself visible, as it is provided with two 

 lips — thin above, thick and crossing below — which lie in such 

 careless yet complete apposition as to hide the groove until the 

 lips are separated. 



The capacity oi the rumen is enormous : ioo litres (22 gallons) 

 can be stored in it in the ox ; 4 to 6 litres (8§ gallons) in the 

 sheep. Its muscular bands are arranged in two diameter-like 

 girdles, and their function is very obviously to contract on the 

 contents. All solid food, on being received from the mouth, 

 enters the rumen ; all fluid substances may enter any or all of 

 the four compartments — viz., they may proceed to the abomasum 

 direct, as is the case in the calf, or they may go to the rumen 

 or reticulum, as most fluids — viz., saliva and the water consumed 

 — do in the adult. Colin assured himself, with his hand in the 

 stomach, through a window in the abdominal wall, that during 

 the first mastication very little passes to the third and fourth 

 compartments, and that little is fluid. Without fluid the rumen 

 can do no work ; cut off the supply, and rumination ceases. 

 This explains the necessity of the enormous salivary secretion 

 in these animals. The rule appears to be that the bulk of the 

 fluid arriving in the stomach is divided between the first and 

 second compartments, the overflow from these passing into the 

 third and fourth sacs. 



