DIGESTION 



20 5 



was considered that the oesophageal groove took an important 

 share in rumination, but the question was decided by Colin 

 in his usual thorough manner by stitching the pillars together, 

 and it was found this did not interfere with the process. Prior 

 to this experiment it was believed that the lips formed the 

 bolus, and then passed it into the oesophagus. Colin, with 

 his hand in the stomach, introduced ingesta into the canal, 

 but could not succeed in getting the lips to grasp and carry it 

 into the oesophagus. Additional 

 evidence is furnished by the llama, 

 which ruminates and has but one 

 pillar to the groove. 



During the churning movements 

 of the stomach the material is being 

 gradually pressed forwards in the 

 direction of the oesophagus and 

 against the lips of the groove, ready 

 for regurgitation. This latter is 

 effected by the diaphragm being 

 hxed in its inspiratory position, 

 and the simultaneous contraction 

 of the walls of the rumen, reticu- 

 lum, and abdomen. By these 

 means some of their contents is 

 forced into the oesophagus, fluid 

 from the reticulum, and semi-solid 

 from the rumen. In the oesophagus 

 the bolus is cut off by the cardiac 

 end of the tube, and by reversed 

 peristaltic action the bolus is con- 

 veyed to the mouth, the soft palate 

 being raised and cutting off the 

 posterior nares. In passing under 

 the velum the liquid portion is 

 squeezed out, and is at once re- 

 swallowed, passing to the third 

 compartment, while the solid 



material is ground. If the left abdominal wall be auscultated 

 during rumination, certain sounds may be heard. One of these 

 Colin describes as resembling a crepitant lung rale, and is due to 

 the disengagement of gas in the rumen ; another is a friction 

 sound resembling that heard in pleurisy, due to the gliding 

 motion of the gastric reservoirs against the abdominal wall and 

 diaphragm ; and a third sound is heard at the moment the fluid 

 returns from the mouth. Gurgling sounds may also be heard 

 over the oesophagus in the neck at the moment of swallowing. 



Fig. 71. — Diagram of the Oeso- 

 phageal Groove, with the 

 Mucous Membrane stripped 

 off to show its muscular 

 Fibres (Carpenter). 



(E, (Esophagus entering the stom- 

 ach ; C, its cardiac opening ; 

 RP, right pillar of oesophageal 

 groove ; LP, left pillar of the 

 same ; O, opening into the 

 omasum ; (EG, oesophageal 

 groove extending from C to 

 O, about 7 inches in length. 



