FOURTH STOMACH IN THE SHEEP, 149 



The fourth stomach, the red or rennet, comes immediately 

 after the third, with which it communicates by a pretty large 

 opening situated at the right extremity of the manyplies, and 

 opposite to its cesophageal orifice. The fourth stomach is of 

 the same size as the honeycomb, but it differs from the other 

 stomachs by its oval form, and by a considerable diminution of 

 its diameter as that approaches the right side. The fourth 

 stomach opens straight into the commencement of the small 

 intestine. The internal surface of this stomach has longitu- 

 dinal folds analogous to those of the manyplies, yet less pro- 

 minent, and entirely destitute of indentations. These folds 

 communicate together by means of small transverse or oblique 

 processes. Towards the pyloric extremity of the stomach the 

 muscular tunic becomes increased considerably in thickness, so 

 as in no small degree to contract the opening. In the ox, the 

 stag, the camel, the lama, as well as in the sheep, there is be- 

 sides in the superior and posterior part of the first portion of 

 the duodenum a rounded collar formed by the lining membrane, 

 which occasions a very sensible diminution of width in the 

 pyloric orifice : there is no such collar in the human struc- 

 ture.* 



Rumination. To explain the mechanism of rumination, 

 three questions require an answer: first, What are the stomachs 

 to which the aliment passes during the first digestion ? secondly, 

 What are the parts which determine its rejection? thirdly, 

 What are the stomachs to which the aliment is transmitted in 

 the second digestion ? 



The answers to these three questions are now, owing to the 

 exact experiments of Flourens, very satisfactory. The aliment 

 which is swallowed for the first time goes exclusively into the 

 first and second stomachs. The aliment which has been rum- 

 inated that is to say, the aliment which is swallowed for the 



* Meckel, ' Anatomic Compares,' torn. ix. p. 433-441. 



