THE KIDNEYS 555 
muscles. In well-hardened specimens, especially those from thin subjects, impres- 
sions of the last two ribs and the tip of the first lumbar transverse process are 
usually visible! The ventral surface (Facies ventralis) is in general slightly con- 
cave, and is related to the liver, pancreas, cecum, and right adrenal; it either has 
no peritoneal covering, or only a narrow peritoneal area laterally.2, The medial 
border (Margo medialis) is convex and rounded; it is related to the right adrenal 
and the posterior vena cava. It presents about its middle a deep notch, the renal 
hilus (Hilus renalis); this is bounded by rounded margins, and leads into a space 
termed the renal sinus (Sinus renalis). The vessels and nerves reach the kidney 
at the hilus, and the sinus contains the renal pelvis or dilated origin of the ureter. 
The lateral border (Margo lateralis) is rounded, and is thinner than the medial one. 
Fic. 495.—D1acram or Position AND Dorsat RELATIONS OF KipNEeys OF Horse. 
Areas of direct relations are enclosed by continuous lines; parts of skeleton which overlie the kidneys are indicated by 
dotted lines. L.J.—L.III, lumbar transverse processes. 
Tt consists of two parts, anterior and posterior, which meet at alateral angle; the 
anterior part fits into the renal impression of the liver. The duodenum curves 
around the lateral border. The anterior extremity (Extremitas cranialis), thick 
and rounded, lies in the renal impression of the liver. The posterior extremity 
(Extremitas caudalis) is thinner and narrower. 
The left kidney (Ren sinister) is bean shaped. It is considerably longer and 
narrower than the right one, and is situated nearer the median plane and further 
back, so that the hilus of the left kidney is usually about opposite to the posterior 
extremity of the right one. It is usually ventral to the last rib and the first two 
1The dorsal surface, being largely in contact with ue diaphragm, slopes downward in front; 
thus its anterior part is about three inches (ca. 6-8 em.) ventral to the dorsal part of the seven- 
teenth rib. 
Tn exceptional cases a considerable area—as much as the outer and posterior third—of the 
surface may have a peritoneal covering. In the new-born foal a large part is so covered; this is 
apparently due to the small size of the caecum and the small area of attachment of its base. 
