in] THE DIGESTIVE ORGANS 43 



l)aratively uudeveloi)ed. This is because the young auiuuil does 

 not ruminate, and lias no need for bulky receptacles for cellulose 

 digestion. 



Rumination is a reflex act, the centre for which is in the 

 medulla. The efferent nerves are the sensory nerves of the rumen. 

 The process depends on the united action of the diaphragm, 

 stomach and abdominal muscles. The amount of food contained 

 in each ascending bolus in the ox is about 3.V to 4 ounces. The 

 formation of the bolus and its ascent to the mouth occupy 

 '^ seconds ; the actual process of chewing the ascended cud 

 generally lasts about 50 seconds ; and the descent of the bolus 

 IJ seconds. Colin has estimated that out of 24 hours, about 

 7 are occupied by rumination. 



During rumination the animal lies slightly on one side, and 

 rests partly on its chest and partly on its abdomen, its fore limbs 

 Ijeing bent under its chest, and its hind limbs brought forward 

 so as to lie partly under its body. This is the familiar attitude 

 of cows chewing the cud. Thej^ are usualh' very timid, and any 

 slight disturbance causes them to get up and rumination is 

 brought temporarily to an end. So also fatigue, or the occurrence 

 of slight maladies or excitement due to oestrus, may interfere 

 ^\dth rumination, and the longer it is delayed the more difficult 

 it is to resume since the food becomes dry and closely packed, 

 so that it is liable to set up local irritation. 



The Small Intestine and the Glands communicating 



^VTTH it. 



The intestinal canal or alimentary canal beyond the stomach 

 is divided into two main parts, the small intestine, and the large 

 intestine. The small intestine is comprised of the U-shaped 

 duodemim which immediately succeeds the pyloric end of the 

 stomach, and the ileum which is considerably longer and is 

 usually much coiled. The middle portion of the small intestine 

 is sometimes called the jejunum. 



The small intestine is composed of the same four coats as the 

 stomach, serous or peritoneal, muscular, submucous, and mucous, 

 the latter being lined internally by a columnar epithelium. 

 There are numerous vascular villi confined to the mucous mem- 

 brane. These are provided with vessels containing lymph, and 



