■URINARY ORGANS OF THE OX 565 



The left kidney occupies a remarkable position, and when hardened in situ 

 differs strongly in form from the right one. When the rumen is full, it pushes the 

 kidney backward and across the median plane, so that it is situated on the right 

 side, behind, and at a lower level than, the right kidney. It then lies usually 

 ventral to the third, fourth, and fifth lumbar vertebrae. When the rumen is not 

 full, the left kidney may lie partly to the left of the median plane. It has three 

 surfaces. The dorsal surface is convex, and presents on its antero-lateral part the 

 hilus, which opens laterally. The ventral surface is related to the intestine. The 

 third face is more or less flattened by contact with the rumen, and may be termed 

 the ruminal surface. The anterior extremity is small, the posterior large and 

 rounded. "^ 



The kidneys are embedded in a large amount of perirenal fat termed the 

 capsula adiposa. The weight of a kidney of an adult animal is about 20 to 25 ounces 

 (ca. 600-700 gm.), the left one being usually an ounce or more the heavier. The 

 two form about -j- per cent, of the body-weight. 



The right kidney measures about 8 or 9 inches (ca. 20-22.5 cm.) in length, 4 to 5 inches (oa. 

 10-12 cm.) in width, and 23/2 to 3 inches (ca. 5-6 cm.) in thickness. The left kidney is one or 

 two inches (ca. 2 to 5 cm.) shorter, but its posterior part is much thicker than the right one. 



Structxire. — The hilus is equivalent to the hilus and sinus of the kidney of the 



Fig. 506.— Cast of Origin of Uheter (a), Calyces Majores, axd Calyces Minores (b) of Ox. (ASter Dumont.) 



horse; in the right kidney it is an extensive elliptical cavity; in the left one it is a 

 deep fissure. The pelvis is absent. The ureter begins at the junction of two wide, 

 thin-walled tubes, the calyces majores; the anterior calyx is usually the larger. 

 Each calyx major gives off a number of branches, and these divide into several 

 funnel-shaped calyces minores, each of which embraces a renal papilla. The 

 space not occupied by the calyces and vessels is filled with fat. 



On section through the kidney the renal pyramids are easily made out. The 

 blunt apex of each pyramid, the renal papilla (Papilla renalis), projects into a calyx 

 minor. On each papilla are small orifices (Foramina papillaria) by which the 

 papillary ducts (Ductus papillares) open into the calyx. The renal columns are 

 much more distinct than in the horse. 



At the hilus the renal artery is dorsal, the vein in the middle, and the ureter 

 ventral; a quantity of fat surrounds these structures in the hilus. 



iThe above statements refer to the adult subject, and are based on investigations made on 

 living subjects, and studies of frozen sections and material hardened m situ. In the new-bom 

 calf the kidneys are almost symmetrically placed, but as the rumen grows it pushes the l^t kidney 

 to the right and backward pari passu. It also usually causes a rotation of the kidney so that the 

 primary dorsal surface comes to lie almost in a sagittal plane Further, the gland is bent so that 

 the hilus is largely closed up and faces outward (to the right). In very fat subjects the three- 

 sided appearance of the kidney may be absent, and about one-third or more may remam to the left 

 of the median plane, even where the rumen is pretty well filled. 



