EUMINATION. 



323 



the first two stomachs is slightly alkaline. Tiedemann and Gmelin 

 found it acid in calves, and Colin says it is also acid when digestion is 

 disturbed, from fermentative change occurring in the food. The food 

 left in the rumen and reticulum is subjected to a slow churning process, 

 and not to the active, grinding movements which were once thought to 

 aid in trituration and regurgitation of food, substances dropped into 

 the posterior pouches of the paunch gradually being forced forward into 

 the reticulum and back again, without any very sensible contractions of 

 the muscular walls of the viscas (Fig. 140). By exposing the interior 

 of the paunch in a young bull, Colin noticed the welling up of the fluid 

 and the production of distinct waves, indicating the commotion set up 



Fig. 140.— Rumen and Reticulum of the Ox, Laid Open by Removing 

 the Left "Wall while in situ. 



A, gullet : B, reticulum ; C, anterior pouch of rumen ; D, middle pouch : E. posterior superior pouch ; F, 

 posterior inferior pouch ; G K, pillars of the oesophageal canal ; I, entrance to the omasum. 



in every portion of the contents. The newly swallowed food is therefore 

 speedily mixed, however long the animal may have fasted, with the por- 

 tions which must necessarily lodge in the lower pouches of the rumen, 

 even in the most perfect digestion (Fig. 141). It is evident that pro- 

 longed maceration in the paunch will reduce food to a pulpy mass, thus 

 facilitating the regurgitation of the food for a second mastication. All 

 soluble materials which the saliva and other fluids swallowed may dis- 

 solve are rendered fit for passage into the alimentary canal, and, how- 

 ever feeble the actions of secretion, the saliva swallowed is here in its 

 most suitable conditions for transforming starchy food into sugar. The 



