ISO NORMAL HISTOLOGY. 



of elongated truncated pyramids between the rays, 

 and in a thin irregular layer of the same appearance 

 directly beneath the capsule. The grayish, pyra- 

 midal portions of the cortex are called cortical pyra- 

 mids, and the entire substance of the cortex, 

 exclusive of the medullary rays, is sometimes called 

 the labyrinth. If the blood-vessels of the kidney 

 have been injected with some colored substance, 

 or if the vessels are well filled with blood, tiny 

 vessels can be seen passing off from the large trunks 

 which lie between the cortex and medulla ; and ex- 

 tending radially toward the surface of the organ 

 through the .centre of the cortical pyramids, and at 

 each side of these vessels, may be seen a row of 

 minute globular structures, which are the Malpighian 

 bodies or glomeruli. 



The human kidney differs from that which we 

 have just described, in that it consists of a number 

 of just such structures crowded together to form a 

 single organ. In embryonic life its composite nature 

 is evident, because each renculus as each portion 

 corresponding to the rabbit's kidney is called is 

 separated from its neighbors by a certain amount of 

 connective tissue, giving the surface of the organ a 

 lobulated appearance. As the individual matures, 

 the renculi usually become merged into one another, 

 so that we no longer see on the surface any trace of 

 its composite character. This is betrayed, however, 

 by the fact that the medullary pyramids of the 



