472 



THE URINARY ORGANS OF THE HORSE 



kidney. It is related to the posterior aorta, the adrenal, and the ureter. The 

 external border is related chiefly to the base of the spleen. The anterior extremity 

 extends almost to the saccus caecus of the stomach; it is related to the left end of 

 the pancreas, and the splenic vessels. The posterior extremity is usually larger 

 than the anterior one. 



The form of the left kidney is variable. In some cases its outline is similar to that of the right 

 kidney, but its ventral surface is convex and is often marked by several furrows which diverge 

 from the hilus. In well-hardened specimens the three areas of the dorsal surface are often dis- 

 tinct. The psoas area is flat, parallel with the inner border, and widens behind. The diaphrag- 

 matic area is small and convex; it is crescentic and is confined to the anterior pole. The splenic 

 area, convex and external, is often so extensive and distinct as really to constitute a third surface. 



Fixation. — The kidneys are held in position chiefly by the pressure of adjacent 

 organs and by the renal fascia. The latter is a special development of the sub- 

 peritoneal tissue, which splits into two layers to inclose the kidney, together with 

 the perirenal fat or capsula adiposa. On account of its relations with the liver. 



Renal crest 



Cortical substance 



Medullary substance 



Accessory 



renal 



artery 



Renal artery 



Ureter 



Fig. .37S. — Frontal (Horizontal) Section of Kidney of Horse. 



The renal vein is removed. A large acce.ssory renal artery entered the posterior pole. Sections of arteries in 



limiting layer between cortical and medullary substance are white in figure. 



pancreas, and the base of the caecum, the right kidney is much more strongly 

 attached than the left one. It is, therefore, not surprising that the latter varies 

 somewhat in position; its posterior pole may be found ventral to the third or fourth 

 lumbar transverse process. The position of the right kidney seems to be very 

 constant, excluding its movements during respiration. 



Weight and Size. — The right kidney is usually one or two ounces heavier than 

 the, left. The average weight of the right kidney is about 23 to 24 ounces (ca. 

 700 gm.); that of the left, al)Out 22 to 23 ounces (ca. G70 gm.). The relation of 

 the weight of Ijoth kidneys to the ]wdy-\^eight is alwut I : 300-350. 



Chauveau gives as an average 7.50 grams for the right kidney, and 710 grams for the left. 

 Ellenberger and Baum (24 cases) give the right kidney as varying between 430 and 840 grams; 

 and the left between 42.5 and 7S0; this is an average of 6:35 grams (about 2232 ounces) for the 

 right kidney, and G02.5 grams (al)out 21^2 ounces) for the left. They give the relation of the 

 weight of both kidneys to the body-weight as 1: 25.5-344. In a Percheron mare weighing about 

 2000 pounds the right kidney weighed 4 pounds 3 ounces, and the left one 4 pounds. In a horse 

 of medium size the right kidney is about six inches (ca. 15 cm.) in length, about the same in width, 

 and about two inches (ca. 5 cm.) thick. The left kidney is about seven inches (ca. IS cm.) long, 

 four to five inches (ca. 10 to 12 cm.) wide, and two to two and a half inches (ca. 5 to 6 cm.) thick. 



