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lie still further caudad. In kidneys of this type the hilus is on the 
ventral aspect and there are always two ureters. 
Considerable irregularity occurs in regard to the renal blood- 
vessels in these cases, both as to their number and origin. As a 
rule the arteries arise from the aorta further caudad than in the 
normal condition, but may arise also from the A. mesenterica inferior 
or the A. iliaca communis. Accessory arteries may come from the 
Aa. sacralis media, hypogastrica and others. 
Buppe (1913) has recently described an early case of horseshoe 
kidney from a human embryo of 19 mm. The caudal poles of the 
kidneys are here fused, the fusion extending over somewhat more than 
a third of the length of the organs. 
The causes of horseshoe kidney are unknown. The embryonic 
stage found by Buppr offered no definite clue, but that author 
suggests that the approximation and fusion may in this instance have 
been due to the influence of neighboring organs. The stomach, for 
instance, seemed to lie unusually far caudad, the lower end reaching 
the middle of the fourth lumbar vertebra. In connection with it are 
to be considered the intestinal loops and the mesenteries. The liver 
was voluminous and extended on each side to the fifth lumbar 
vertebra. Unusual pressure may thereby have been exerted upon the 
renal anlages. 
The fact that horseshoe kidneys are situated usually at a lower 
level than the normal, and that the renal arteries in these cases arise 
further caudad, has led to the conclusion that fusion occurs at an 
early stage, the abbreviated forward migration being a consequence 
of the fusion. The ventrally facing hilus furthermore limits the fusion 
to a period before the rotation of the kidneys into the horizontal 
plane had been completed. 
Description. 
I. Pelvic kidney. 
The following case occurred in an adult male cat. 
The left kidney occupies the normal position and the renal artery 
and vein have the usual relationships. The adrenal bodies are both 
normally situated. 
The right kidney is situated in the pelvic cavity, in the bifur- 
cation of the aorta. It closely resembles in position the pelvic kidney 
