324 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



changes of the food in this stomach are probably of a fermentative 

 nature, as indicated by the nature of the gases which are constantly 

 present. Thus, C0 2 , H 2 S, acetic acid, butyric acid, carbonate of ammo- 

 nium, chlorides, carbonates, phosphates and sulphates of sodium and 

 potassium, and carbonates and phosphates of lime, are almost constantly 

 found. The solids will, of course, vary in relative abundance according 

 to the food which has served as a diet for the animal. In the reticulum, 

 also, the food undergoes changes similar to those which have been ob- 

 served in the rumen ; in fact, the reticulum may be regarded as an exten- 

 sion of the paunch. Its special function appears to be to retain fluids, 

 as its contents are always liquid. Its reaction is also alkaline. 



Fig. 141.— Vertical Section of the Rumen and Reticulum. {Colin.) 



A B, superior region ; C D, median region ; E F, inferior region ; G II, the small arrows show the course followed by thi 

 food which passes from the posterior portions of the rumen to be ruminated. 



As regards the mechanism of the rejection of food for the second 

 mastication, considerable diversity of opinion prevails. All authors, 

 however, agree in dividing the organs of rumination into the essential 

 organ — the stomach, and the auxiliary organs — the diaphragm and ab- 

 dominal muscles. It is not perfectly clear from which compartment the 

 food enters the oesophagus to be ruminated. 



Colin, Chauveau, and others believe that it passes directly out of the 

 rumen into the oesophagus, while Haubner thinks that the assistance of 

 the water-bag is essential, and this seems most probable on anatomical 

 grounds. The rumen is an organ of immense size, and, as has been shown, 

 may contain as much as two hundred pounds of material, and its muscular 



