INTERIOR 457 
tensive chief pillars project like shelves into the anterior and posterior ends of the 
cavity, forming the blind sacs at either extremity. The anterior pillar (Pila cranialis) 
projects obliquely backward and upward from the ventral wall, and has a thick, 
concave free edge which is opposite to the tenth and eleventh ribs. Its width from 
the middle of the free edge to its attached border is about eight to ten inches (ca. 20 
to 25 em.). It is continued on either side by the relatively narrow longitudinal 
pillars (Pila dexter, sinister), which connect it with the posterior pillar. The 
posterior pillar (Pila caudalis) is more nearly horizontal than the anterior one, and 
separates the large dorsal and ventral posterior blind sacs. Its concave free border 
is about a hand’s breadth in front of a transverse plane through the tuber coxe. 
From it are detached three accessory pillars on either side; of these, two pass around 
the blind sacs to meet the corresponding pillars of the opposite side. They thus 
s'\Reficulum 
NS 
Fic. 389.—TuHoracic AND ANTERIOR ABDOMINAL VISCERA OF Ox; DeEp DISSECTION. 
Most of the rumen has been removed and the left wall of the reticulum cut away. A., Left pulmonary artery; 
B., left bronchus; V. V. V., pulmonary veins; b. 6., bronchial lymph glands; L. g., posterior mediastinal lymph gland; 
D., termination of duodenum; F, rumino-reticular fold. 
mark off the posterior blind sacs from the general cavity, and are termed the 
coronary pillars (Pila coronaria dorsalis, ventralis). It will be noticed that the 
ventral coronary pillar is complete, while the dorsal one is not. The other accessory 
pillars join the right and left longitudinal pillars. The right longitudinal pillar is 
in part double; its ventral division fades out about the middle of the surface, while 
the dorsal one joins the posterior pillar. The distance between the middles of the 
anterior and posterior pillars is only about sixteen to eighteen inches (ca. 40 to 45 
em.) in a cow of medium size. In this space the dorsal and ventral sacs communi- 
cate freely. 
The anterior end of the dorsal sac of the rumen is separated ventrally from the 
reticulum by an almost vertical fold formed by the apposition of the walls of the 
two compartments. This rumino-reticular fold (Pila rumino-reticularis) is oppo- 
site to the seventh or eighth rib.!_ Its free dorsal edge is concave and forms the 
‘ The position of this fold naturally varies with the degree of fulness of the reticulum. When 
the latter is full, it may extend back in part to the eighth intercostal space. 
