URINARY ORGANS OF THE DOG 483 



on either side of the first four lumbar vertebrae. (Variations in position are not rare, 

 and involve the left kidney oftener than the right. The former has been found 

 near the pelvic inlet.) The external border lies against the flank parallel with the 

 edge of the longissimus muscle. The posterior extremity usually lies about mid- 

 way between the last rib and the external angle of the ilium. The anterior ex- 

 tremity of the right kidney usually extends as far forward as the last rib, but has 

 no contact with the liver. 



The weight of the kidney of a medium-sized pig is about seven to nine ounces 

 (200 to 250 grams). The ratio of their combined weight to that of the body is 

 about 1 : 150-200. 



Structure. — The hilus is about in the middle of the inner border. The pelvis 

 is funnel-shaped, ami divides into two calyces majores, which pass in a curve for- 

 ward and backward respectively, and give off some eight to twelve short calyces 

 minores ; each of the latter contains a papilla Some papillae are narrow and coni- 

 cal, and correspond to a single pyramid ; others are wide and flattened, and result 

 from the fusion of two or more pyramids; some project directly through the wall 

 of the pelvis without the formation of a calyx. The renal pyramids are distinct, 

 but it is apparent that some are compound, i. e., formed by fusion of primitively 

 separate pyramids. The renal artery enters the ventral part of the hilus, and the 

 ureter leaves it dorsally. 



The only special feature in regard to the ureter is that it is at first relatively 

 wide and gradually diminishes in caliber. 



The bladder is relatively very large; when full, it lies chiefly in the abdomi- 

 nal cavity. It is almost completely covered with peritoneum. 



URINARY ORGANS OF THE DOG 



The kidneys are relatively large, forming about j\^ to 77 i^^ of the body-weight; 

 the weight of the kidney of a medium-sized dog is about two ounces (ca. 50 to 60 

 grams). They are both bean-shaped, thick dorso-ventrally, with a rounded ven- 

 tral surface and a less convex dorsal surface; the surfaces are smooth. 



The right kidney (Fig. 343) is not subject to much variation in position; it 

 is situated usually under the last rib and the first three lumbar transverse processes. 

 Its anterior part lies in the deep renal impression of the liver; its posterior part is"^ 

 related to the sublumbar muscles dorsally, and the pancreas and duodenum 

 ventrally. 



The left kidney (Fig. 342) is subject to some variation in position; this is due 

 to the fact that it is loosely attached by the peritoneum, and is affected by the de- 

 gree of fullness of the stomach. When the stomach is nearly empty, the kidney 

 usually lies under the transverse processes of the second, third, and fourth lumbar 

 vertebrae, so that its anterior pole is opposite to the hilus of the right kidney. As 

 the stomach fills it pushes the left kidney backward, so that the anterior pole of 

 the latter may be opposite the posterior pole of the right kidney. The dorsal 

 surface is related to the sublumbar muscles. The ventral surface is in contact 

 with the terminal part of the colon (Colon descendens). The external border is 

 related to the spleen and the flank. The anterior extremity touches the stomach 

 and the left extremity of the pancreas. 



The external border of the left kidney has considerable contact with the flank, and hence 

 it may be palpated more or less distinctly in the living animal about half-way between the last 

 rib and the crest of the ilium. 



Structure. — The hilus is in the middle of the inner border and is, relatively 



