466 TEE DIGESTIVE APPARATUS IN MAMMALIA. 



email mammiform tubercles; they are absent on the muscular columns?. This papillary 

 arrangement is still more developed in certain wild Ruminants, and it is scarcely possible to 

 give an idea of their richness in the stomach of Gazelles. 



The interior of the rumen otfers for study two openings, situated at the anterior extremity 

 of the left sac : one is the oesophageal orifice, pierced in tlie superior wall, dilated into an 

 infundibulum, and prolonged into the small curvature of the reticulum by a particular furrow 

 (or channel), which will be describeil after the latter compartment ; tlie other, placed below, 

 and opposite the preceding, traverses the bottom of the cul-dt-sac from before to behind, and 

 forms the communication between tiie paunch and reticulum : it is a very large opening, cir- 

 cumscribed below and on the sides by a septum or semilunar valve, resulting from the junction 

 of the parietes of the rumen with those of the reticulum. 



Structure. — Like all the hollow organs in the abdomen, the rumen has three tunics: a 

 serous, a muscular, and a mucous. 



The i<erous envelops the organ throughout, except above, in front, and to the left, the point 

 which touches the sublumbar region, and the pillars of the diaphragm, as well as the bottom 

 of the notches which separate the culs-de-sac from tlje extremities. This membrane gives 

 origin, like that of the stomach of tiie Horse, to a vast duplicature — the great omentum. The 

 arrangement of this, which is somewhat diflQcult to observe in the Ox, in consequence of the 

 enormous weight of the gastric mass, is readily seen in the smaller Ruminants. It begins at 

 the middle of the faces of the paunch and the fissure intermediate to tlie two conical cysts, 

 forming a wide envelope that contains the right sac and the abomasum ; it becomes attached in 

 passing over the great curvature of the last-named cavity, and is confounded, superiorly and 

 posteriorly, with the great mesentery. 



The muscular coat is very thick, and forms the internal columns of the viscus. Its fibres 

 are disposed in several layers, wiiose arrangement is simple, and offers nothing really interest- 

 ing to study, except in the points where the serous tunic passes from one cul-de-sac to another, 

 or from the rumen to the reticulum ; there it is often accompanied by tliin and wide muscular 

 fasciculi which, like the latter membrane, stretch over the intermediate fissures, and thus 

 become real unitive or common fibres. 



The muscular fibres of the rumen present an unmistakable transverse striation — a very 

 rare physical characteristic in the muscular tissue of organic life. 



'J he mucous membrane ofiers some peculiarities, which deserve a few words. The corium 

 is very thick, and probably contains some glands, but they must be extremely few. The free 

 face of the membrane is excessively uneven, in consequence of the papillary apparatus mentioned 

 above. 



The papillsB of the rumen are foliaceous, conical, fungiform. Those of the first description 

 are much more numerous than the others; they have the shape of an oval, elongated leaf; their 

 summit is wide and rounded, and the base narrow and apparently implanted in the corium. 

 On one face is a little rib that springs from the base and disappears on the widened portion, 

 resembling the principal vein or nervule of a leaf. On the other face, opposite the vein, is a 

 faint longitudinal groove. 



These papilije are constituted by a layer of nucleated connective tissue, covered by epitlie- 

 lium ; the former, in the principal papillae, has on its faces and extremities minute prolonga- 

 tions, resembling on a small scale the secondary papillae described as existing on the lingual 

 mucous membrane. In the centre of the papillae are one or two main arteries, derived from the 

 network of the corium. These pass, in a slightly tiexuous manner, to the summit, and break 

 up into several branchlets, succeeded by veins, that descend along the surface of the papilla 

 into each of its secondary prolongations. 



The conical and fungiform papillae are few in the left sac, and resemble the papillae of the 

 same name desciibed on the tongue. 



The epithelium of the mucous membrane of the rumen is remarkable for its strength and 

 cohesiveness. It belongs to the category of stratified tesst lated epithelium, and forms a sheath 

 to each papilla, covering the corium in the interpapillary spaces. 



There are frequently found, in opening the rumen of animals just killed, large exfoliated 

 patches on the surface of this layer. This is a suflScient indication of the activity of the 

 secretion of the epithelium, and tlie rapidity of its renovation. 



RETicrLUM (Honeycomb) (Figs. 268, 269, 270). Situation— Form— Eelations.— This, the 

 smallest compartment, is elongated from side to side, slightly curved on itself, and placed 

 transversely between the posterior face of the diaphragm, in one direction, and the anterior 

 extremity of the left sac of the rumen in the other; the latter only appearing, externally, to 

 be a prolongation, or a diverticulum of the rumen. 



It has two faces, two curvatures, and two extremities. The anterior face adheres to the 



