DIGESTION 197 



quence, the movements of the compartment are not only powerful, 

 but energetic. The mucous membrane on its interior is arranged 

 in polyhedral cells 10 to 15 mm. in depth, closely resembling 

 a honeycomb. In these cells stones, gravel, and foreign bodies 

 may frequently be found, the latter frequently penetrating the 

 heart. 



The contents of this compartment are fluid and alkaline, the 

 fluid being derived from that swallowed, and from the rumen ; 

 the alkaline reaction is due to the saliva, for, so far as we know, 

 the mucous membrane possesses no secretory activity. The 

 fluid in the reticulum is of use in rumination, and is forced into 

 the oesophagus by a contraction of the walls of the viscus ; it 

 may also be forced into the rumen. Colin, with his hand in this 

 sac, the presence of which produced energetic contractions, found 

 the fluid poured over his hand, flooding the contents of the 

 rumen. In order that fluid may be retained in this bag, the 

 openings out of it are situated considerably above the base of the 

 organ ; and, further, the reticulum is so situated relatively to the 

 rumen that it receives the overflow of fluid from that compart- 

 ment when it contracts. 



Ellenberger is of opinion that the reticulum regulates the 

 passage of food from the first to the third compartment, and 

 from the rumen to the oesophagus. In transferring the contents 

 of the rumen to the omasum, the reticulum contracts and forces 

 the material into the oesophageal groove. Flourens showed that 

 the reticulum was not essential to rumination, for he excised it 

 in a sheep, and rumination was not interfered with. 



The Omasum, or third compartment, is quite different from 

 those hitherto examined. Placed between the reticulum and 

 abomasum, the viscus does its work with its contents inverted. 

 The openings into and out of a stomach or diverticulum are 

 generally above the portion holding the contents, but in the 

 omasum the contents are above the openings which lead into and 

 out of it. The omasum defies the laws of gravity. 



This third compartment communicates anteriorly with the 

 second and posteriorly with the fourth, by means of a canal 

 three or four inches long, which runs obliquely backwards, 

 downwards, and to the right. It is over this canal that the 

 structure of the omasum is placed. The interior arrangement 

 of the organ is most singular, being composed of several large 

 leaves running the length of the organ, between these are smaller 

 leaves, and between these a third and then a fourth series. 

 Altogether about one hundred laminae of variable size are found 

 in the compartment. The leaves are papillated, the papillae 

 at the reticulum end being large, horny, and pointed ; towards 

 the omasum end they lose the pointed character and become 



