420 



PHYSIOLOGY 



CHAP. 



easily be detached, since it is only connected with the substance of 

 the gland by minute processes of connective tissue and small 

 vessels. If split up longitudinally, it presents the anatomical 



features shown by 

 Fig. 109. The cor- 

 tical substance is 

 reddish - brown, the 

 medullary pale and 

 fibrous. In man the 

 latter consists of 

 about ten Malpig- 

 hian pyramids, the 

 points of which con- 

 verge towards the 

 pelvis which receives 

 the secretion. An 

 intermediate layer 

 can be distinguished 

 from the cortical and 

 medullary substance, 

 exhibiting character- 

 istics common to both 

 (Henle). 



Each Malpighian 

 pyramid consists of a 

 large bundle of urini- 

 ferous tubules, which 

 are straight in the 

 medullary part 

 (tubuli recti of 

 Bellini), and con- 

 voluted in the corti- 

 cal part (tubuli con- 

 torti of Ferrein). The 

 straight tubules of 

 the pyramids are 

 prolonged into the 

 cortical substance 

 almost to the surface 



FJG. 110. Diagram of course of two uriniferous tubules. (Klein.) of the kidney, where 

 A, cortex ; B, boundary zone ; C, papillary zone of medulla; .1 f .-,'! n j^l 



a, a't superficial and deep layers of cortex, free from glomeruli. trie y I0rm ine mCC 



lary rays, visible to 



the unaided eye, from which the convoluted tubules deflect to 

 form the labyrinth of the cortex. 



Fig. 110 gives a diagram of the course of the uriniferous 

 tubules from their origin in the Malpighian corpuscles (Bowman's 

 capsules enclosing the vascular glomerulus) to their opening upon 



