SEMIOLOGY OF THE DIGESTIVE APPARATUS. 113 



and analysis of the liquids removed by aspiration (first stages of gastric 

 digestion). Normally, these gases, in the order of their abundance in the 

 mixture, consist of the follo^Ying : Carbonic acid, carburetted hydrogen 

 and nitrogen. 



In disease, and in most cases of abnormal fermentation, the carbu- 

 retted hydrogen is greatly in excess of the carbonic acid. In chronic 

 gastro-enteritis, ammonium sulphide and other offensive gases are found 

 in addition. 



Chemical analysis. In the rumen the ingested food is macerated in 

 an alkaline liquid at a temperature of 100° to 101° Fahr. (the alkalinity 

 is due to the saliva) , This process markedly modifies the composition of 

 the ingested matter. Nevertheless, the upper portion in contact with the 

 gas sometimes presents a slightly acid reaction, probably due to carbonic 

 acid. The sugary and fatty materials contained in the food respectively 

 undergo lactic and butyric fermentation. Only a small quantity of the 

 starch, however, is transferred into sugar. In the calf, and in very young 

 animals, the reaction of the rumen is acid throughout the entire period 

 of sucking. In disease, when rumination has long been suspended and 

 chronic loss of appetite or gastro-enteritis exists, the reaction is generally 

 acid. The sugars, gums, and soluble salts of forage, roots, etc, are dis- 

 solved in the rumen, but fatty materials undergo no modification. 



The reticulum, which is the smallest of the gastric compartments, is 

 situated in the sub-ensiform and retro-diaphragmatic regions, extending 

 right and left of the middle line to a nearly equal distance. Above and 

 to the left it communicates freely with the rumen, to the right with the 

 omasum. 



In practice it can only be examined in two ways : inspection and 

 palpation. 



By inspection changes in the configuration of the ensiform region 

 may sometimes be detected. Such changes are rare, and must be dis- 

 tinguished from congenital deformity. They sometimes accompany 

 inflammation of the reticulum produced by a foreign body, when the 

 lower abdominal wall is directly perforated by such body. 



In cases of inflammation of the reticulum due to foreign bodies, 

 abscess formation, perforation, etc., it is possible to detect cedematous 

 infiltration, abnormal sensibility, fluctuation and increased heat, etc., by 

 manipulating the parts with the fingers or the clenched fist. 



If the evidence pointing to the presence of a foreign body in the 

 reticulum is considered sufficient, gastrotomy may be performed and the 

 interior of the viscus examined with the hand, but although the operation 

 is i^ossible it is very rarely practised. 



Omasum. The omasum occupies, so to speak, a position inverse to that 



D,C. . I 



