THREE FIGUXES
Congenital anomalies of the kidney are known to occur frequently in man. They have been described and classified in considerable detail, and the relative frequency with which various types occur has been established. Comparable data from non-human material are extremely meager, however, even for the well known laboratory animals.
In man one of the common renal anomalies is fusion of the kidneys across the midline to form a so-called "horseshoe" kidney. Since the report of Berengarius (1521) more than 500 cases have been published (Boyden, '31). According to Bell ( '41) the incidence is approximately one in 400. Johnson ('14) appears to have been the first to describe fusion of the kidneys in the domestic cat. He records one instance of fusion out of 400 cats dissectcd in laboratory routine, but his illustration plainly shows a four-lobed, posteriorly fused kidney that bears little resemblance to the horseshoe kidney of human pathology. Ekman ('28) described a "cake-shaped" kidney with crossed dystopia in a domestic cat in great detail. His attempts to explain the origin of this structure and the associated vascular anomalies are marred, however, by his lack of familiarity with the important work of English and American anatomists.
The nearly perfect case of horseshoe kidney described below was discovered during routine laboratory dissection. I am indebted to Dr. H. J. Eigenbrodt, of North Central College,