THE STOMACH. 181 



limply an appendage of the former. The oesophagean canal which 

 leads from the second stomach to the third, performs a very im- 

 portant function in the act of rumi- 

 nation, or it is supposed with reason 

 so to do, as will be explained further on. 

 The third stomach or "manyplies," 

 in the sheep the smallest of the stom- 

 achs, is lined with a number of leaves 

 or folds, placed lengthwise, by which 

 the surface is greatly increased. The 

 fourth stomach joins the third, and 

 communicates with it by an opening 

 immediately opposite to the oesopha- 

 gean orifice. The fourth stomach is 



lined with a membrane which secretes Fig. 72. INTERIOR OP THB 

 the gastric juice, the true digestive STOMACH. 



solvent. It opens directly into the duodenum or small intestine. 



Rumination, or chewing the cud, is a process which distinguishes 

 a class of animals, known as ruminants, from all others. For the 

 performance of this process the complicated stomach above de- 

 scribed is provided. To understand this important alimentary 

 process, it is necessary to ascertain first, into which of the stom- 

 achs the food passes after its first mastication ; second, in what 

 manner and by what process the food is rejected by these stom- 

 achs and returned to the mouth for a second mastication ; third, 

 to which of the stomachs is the food finally transmitted for com- 

 plete digestion. 



Soms careful experiments, by the French physiologist, Flourens, 

 have to a great extent determined these questions ; and the com- 

 parative anatomist, Chauveau, has summed up the functions of the 

 stomachs of ruminants as ascertained from every modern source 

 of information as follows : 



1st. The rumen is a sac in which the food swallowed during 

 feeding time is held in reserve, and is softened, and whence it is 

 carried to the mouth during rumination. 



2nd. The reticulum partakes of the functions of the rumen, to 

 which it plays the part of an accessory or reservoir ; the food con- 

 tamed in it being always diluted by a larger quantit}'- of water. 



3rd. The wsopTiagean canal carries into the omasum the food 

 swallowed the second time, or after rumination, or even those por- 

 tions of food which the animal swallows in very small quantity and 

 in a finely divided or softened condition the first time. 



