THE EXCRETORY SYSTEM 183 



and extends from the eleventh dorsal to the third lumbar 

 vertebra. The right kidney is a little lower than the left, 

 in consequence of the large space occupied by the liver. 

 The kidneys are covered by a tough envelope of fibrous 

 tissue called the capsule of the kidney, and are usually 

 embedded in a considerable quantity of fat. 



b I m 



FlG. 93. Kidney, longitudinal section, exhibiting general relations of 

 microscopic details (after Piersol) : A, Renal artery; U, ureter; C, one of 

 the calices, into which a papilla projects; i, cortex containing labyrinth (/) 

 and medullary rays (m) ; 2, medulla ; M, Malpighian pyramids, some ob- 

 liquely cut at 3, 3 ; b, boundary layer ; B t columns of Bertini ; 4, masses of 

 adipose tissue ; 5, 5, branches of renal artery (after Henle). 



Structure of the Kidneys. The kidney is made up 

 of an outer part, the cortex, and an inner part, the medulla. 

 Its substance is composed of a mass of uriniferous tubules 

 and Malpighian bodies. The Malpighian bodies (Fig. 94) 

 are located in the cortex of the kidney near the surface, 

 and consist of a tuft of blood-vessels, the glomerulus, and 

 an expansion of the uriniferous tubule, which forms a 

 covering about the glomerulus. The uriniferous tubules, 



