140 A Manual of Veterinary Physiology. 



squeezed out and is at once res wallowed, and passes to the 

 third stomach, whilst the solid mass undergoes grinding. 

 After the bolus is reswallowed, it may either pass again to 

 the rumen, or, if in a rinely comminuted condition, it passes 

 at once from the oesophagus into the third stomach. 



Flourens excised the reticulum, but this did not interfere 

 with the process of rumination. 



Rumination can only be performed by means of the 

 united action of the walls of the stomach, abdominal walls, 

 and diaphragm ; it is impossible when the abdominal 

 muscles or the Avails of the stomach are paralysed ; it can 

 occur if the diaphragm be paralysed, but only through an 

 extra effort of the abdominal muscles. The pillars of the 

 diaphragm of the ox are specially arranged, so as to prevent 

 compression of the oesophagus when the diaphragm con- 

 tracts (Steel).* Further, rumination is only possible when 

 the stomach contains a fair amount of food and a con- 

 siderable quantity of liquid. 



The ascent of the food in the oesophagus can be dis- 

 tinctly seen in the neck, and a sound may be heard on 

 auscultation over the region of the oesophagus, due to the 

 passage of the bolus with its fluid admixture. The amount 

 of each bolus has been estimated by Colin at 3 h ozs. to 

 4 ozs. Its formation in the stomach and ascent will occupy 

 about three seconds, and its descent after remastication 

 one and a half seconds ; its remastication occupies about 

 fifty seconds. Altogether, Colin has calculated that a 

 period of at least seven hours is required for the process 

 of rumination. 



During rumination the parotids secrete, but not the 

 submaxillar}' - or sublingual glands. 



Rumination is a reflex nervous act, the centre of which 

 is probably in the medulla. The nerves in the rumen 

 convey the sensation to the brain by means of the pneumo- 

 gastrics, which if divided cause rumination to be sus- 

 pended. 



The Nervous Mechanism of the Stomach.— ( >f this we know 

 • Diseases of the Ox' J, II. Steel. 



