396 THE DIGESTIVE APPARATUS IN MAMMALIA. 



lateral branches diverge to the right and left in describing a curve, and in circumscrib- 

 ing the entrance to the conical cysts, which they transform into two compartments 

 distinct from the middle portion of the sacs of the rumen ; the inferior go to meet the 

 superior brandies, but do not altogether join them. 



The internal surface of the rumen is covered by a multitude of papillary prolongations, 

 dependencies of the mucous membrane. To the right, and in the culs-de-sac, these 

 papillae are remarkable for their number, their enormous development, and their general 

 foliated shape. On the left side they are more rare, particularly on the superior wall, 

 and only form very small mammiform tubercles ; they are absent on the muscular 

 columns. This papillary arrangement is still more developed in certain wild Kuminants, 

 and it is scarcely possible to give an idea of their richness in the stomach of the 

 Gazelle. 



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

 extremity of the left sac : one is the cesophageal orifice, pierced in the superior wall, 

 dilated into an infundibulum, and prolonged into the tmall curvature of the reticulum 

 by a particular furrow (or channel), which will be described after the latter compart- 

 ment ; the other, placed below, and opposite the preceding, traverses the bottom of 

 the cul-de-sac from before to behind, and forms the communication between the paunch 

 and reticulum : it is a very large opening, circumscribed 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 serous 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 the extremities. This 

 membrane gives origin, like that of the stomach of the Horse, to a vast duplicature 

 the great omentum. The arrangement of this, which is somewhat difficult 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 the 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, whose arrangement is simple, and offers nothing 

 really interesting 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 thin 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. 



The mucous membrane offers 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 papillae of the rumen are foliaceous, conical, or 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 wMe 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 papillae are constituted by a layer of nucleated connective tissue, covered by 

 epithelium ; the former, in the principal papillae, has on its faces and extremities minute 

 prolongations, resembling on a small scale the secondary papillse described as existing 

 on the lingual mucous membrane. In the centre of the papillse are one or two main 

 arteries, derived from the network of the corium. These pass, in a slightly flexuous 

 manner, to the summit, and break up into several branchlet?, succeeded by veins, that 

 descend along the surface of the papilla into each of its secondary prolongations. 



The conical and fun;iform papillse are few in the left sac, and resemble the papillse 

 of the same name described 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 tesselated 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 



