THE STOMACH. 469 



a right extremity, continuous with the base of the abomasum, from wliich it is separated by 

 a constriction analogous to that of the anterior extremity, but much less marked. 



Interior. — This compartment shows, in its interior, the two apertures placed at its extre- 

 mities. The right orifice, opening into the abomasum, is much wider than the left, which 

 communicates with the reticulum. The cavity which these orifices bring into communication 

 with tlie adjoining compartments, offers one of the most curious arrangements met with in the 

 viscera ; it being filled by unequally developed leaves of mucous membrane, which follow the 

 length of the cavity. These leaves have an adherent border attached either to the great 

 curvature or to the faces of the organ, and a free concave border turned towards the lesser 

 curvature. They commence at the side of the orifice of the reticulum by denticulated ridges, 

 between which are furrows, and which are prolonged from the base of the leaves to the entrance 

 of the abomasum. At the latter aperture they disappear altogetlier, after rapidly diminishing 

 in height. Their faces are studded by a multitude of very hard mamillary papillse, resembling 

 grains of millet, which are more developed and conical on some of the leaves than others. 

 All these lamellar prolongations are far from being of the same extent ; twelve to fifteen are 

 so wide that their free border nearly reaches the lesser curvature of the viscus, and between 

 these principal leaves are others which, thoui<h regularly enough arranged, are more or less 

 narrower. At first there is remarked a secondary leaf, half the width of the chief ones, 



Fig. 272. 



it - ^ ^ 'll 



SECTION OF THE WALL OF THE OMASUM OF THE SHEEP (FROM THE GREAT CURVATURE, 

 SHOWING THE ORIGIN OF THE LEAVES). 



P, peritoneum; m, the two musular layers; e, epithelium. I, 1, Principal leaves at their origin; 

 2, secondary leaf; 3, 3, leaves of the third order; 4, denticulated lamina; 5, 5, two planes of 

 muscular fibres ascending into the principal leaves, some issuing from the muscular layer of the 



between which it is placed ; then, on each of its sides, another, one-half narrower ; and, lastly, 

 at the base of these, two denticulated laminae more or less salient. In a general way, the 

 leaves which are inserted into the great curvature are tlie longest and widest ; and those 

 attached to the faces of the viscus become shorter and narrower as they draw nearer the lesser 

 curvature. The space comprised between these prolongations is always filled by very 

 attenuated alimentary matters, which are usually impregnated by a very small quantity of 

 fluid, but are also often dry, and sometimes even hardened into compact flakes. 



Structure. — The serous layer is a dependency of the peritoneum, and offers nothing par- 

 ticular; it does not completely cover the anterior face. 



The muscular tunic is much fasciculated, and thin. It is formed by two layers of fibres 

 ■which do not pass in the same direction, and dependencies of this tunic pass into the substance 

 of the leaves which fill the cavity of this compartment. 



The mucous membrane is remarkable for the thickness of its stratified tesselated epithelium; 

 all the leaves are formed by two layers of this membrane, laid one against the other ; and 

 as their structure is interesting, we will notice it. 



The principal leaves are composed of this duplicature of mucous membrane, and two 

 layers of muscular fibres between ; these layers are opposite each other at the commencement 

 of the leaf, and separated by a tr.msverse vessel; in the remainder of their extent they are 

 kept apart by the vessels that pass towards the border of the leaf. Their fibres are detached 

 from the surface of the muscular tunic and, at certain points, from its deep layer. In the 



