MAMMILLARY CONES OF KIDNEY. 257 



with the kidney the ureter dilates that is, as it approaches the 

 hilum, or aperture at the inner concave part of the kidney ; the 

 funnel-shaped cavity which it forms being termed the pelvis of 

 the kidney. The pelvis of the kidney is a cavity lined with 

 mucous membrane, which, on the side of the kidney, divides 

 first into two or three principal short branches that again 

 divide into a larger number of smaller tubes, and these com- 

 municate with the apices of the mammillary cones converging 

 towards this part of the kidney. Into the interior extremities 

 of these smaller subdivisions of the pelvis of the kidney the 

 apices of the mammillary cones enter, two or three sometimes 

 projecting into one, so that the number of the subdivisions of 

 the pelvic cavity is less than that of the mammillary cones. 



Each mammillary cone is found to be occupied by a system 

 of tubes, the tubuli uriniferi dividing and subdividing in a 

 divaricate manner from the small number of trunks that open 

 at the apex into the corresponding subdivision of the pelvic 

 cavity. From the base and sides of the mammillary cones the 

 minute tubuli uriniferi pass into the cortical substance, where, 

 from being before straight and radiating in their course with- 

 out anastomosing, they at once become convoluted in a very 

 intricate manner, with very free anastomoses. The blood-vessels 

 ramify on the walls of these minute tubuli. The sanguiferous 

 system of the kidney is somewhat intricate. The renal artery 

 dividing at the hilum into four or five branches, the vessels 

 proceed between the medullary cones towards the cortical sub- 

 stance, and at the bases of the pyramids form a number of 

 anastomotic arches, the numerous branches derived from which 

 ramify through the cortical substance, and end in a system of 

 capillary vessels that form a network on the uriniferous tubes 

 throughout the whole substance of the kidney. In the medul- 

 lary portion, where the uriniferous tubes are straight, the 

 capillaries form oblong meshes ; but in the cortical substance 



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