184 STUDENTS HISTOLOGY 



pyramids, and in the cortical columns. These arterial trunks arch 

 over the bases of the pyramids of Malpighi, forming the arterial 

 arcade. From these arches small, straight branches are sent 

 outward toward the capsule of the kidney, occupying a position 

 midway between the pyramids of Ferrein, in the labyrinths. The 

 last are the interlobular arteries. During their course, they send 

 off side arteriole s, which penetrate the capsule of the Malpighian 

 bodies. Each afferent arteriole breaks up into a fine plexus the 

 tuft or glomerulus. The glomerulus does not entire^ fill the 

 capsule; so that a space remains between the spherical mass of 

 capillaries and the flattened cells lining the body. The glomeruli 

 are enveloped with a single layer of flattened epithelial cells. 



The blood escapes from the glomerulus by a minute efferent 

 arteriole which emerges from the capsule close to the afferent ves- 

 sel. The latter is the more noticeable, as it is usually much the 

 larger. The efferent arteriole immediately breaks up into a cap- 

 illary plexus, which courses between the uriniferous tubules of 

 the labyrinths and of the pyramids of Ferrein. This plexus also 

 descends between the elements of the pyramids of Malpighi. 

 From the arteries forming the arcade another set of branches 

 the arteriolce rectce is given off, which, descending into the Mal- 

 pighian pyramids, provides another and direct arterial supply to 

 the tubular elements by elongated capillary loops. 



The course of the venous trunks is not unlike that pursued by 

 the arteries. Interlobular veins, lying in the cortical labyrinths 

 parallel with and close to the arteries, pass into a venous arcade. 

 In the medulla the venous blood is collected from the capillaries 

 and carried to the bases of the Malpighian pyramids in small 

 veins venulce rectce. The blood from the cortical intertubular 

 capillaries is collected in the interlobular veins. 



A peculiar vascular arrangement exists just beneath the cap- 

 sule of the kidney, consisting of scattered venous plexuses, the 

 venoe stellatce. They contain blood collected from contiguous 

 intertubular capillaries, and are in connection with the summits of 

 the interlobular veins. 



From what has been said, it will be seen that the cortical and 

 medullary blood -supplies are, to a certain extent, independent of 

 each other. The arteriolaB rectae provide a vascular supply to the 

 elements of the Malpighian pyramids even after many of the 

 glomeruli have become obliterated by disease. 



Nerve and lymphatic elements are not very prominent features 



