122 PRACTICAL MICROSCOPY. 



infundibulum into several calyces. Each calyx the site of the apex of 

 a Malpighian pyramid. 



4. The blood-vessels entering and leaving the hilum. Their subdi- 

 vision outside the pelvic lining, and final passage into the kidney sub- 

 stance in the cortical columns. 



5. Division of kidney substance into cortex and medullary or Mal- 

 pighian pyramids. 



6. Penetration of cortical tissue inward between pyramids of Mal- 

 pighii constituting the cortical columns. 



5. The pyramids of Ferrein. 



6. The labyrinths. 



In the domestic animals there are no cortical pyramids the pyra- 

 mids of Malpighii coalescing, as it were thus presenting a true 

 medulla. 



I have remarked that the kidney is made up largely of urine-carry- 

 ing vessels (the tubuli uriniferi) and blood-vessels. We will first 

 study the tubular system, reserving for the present the consideration 

 of the blood-vessel arrangement. 



THE TUBULI UKIXIFERI. 



The urine-carrying tubules commence in the cortex, and, after tak- 

 ing a very circuitous route with frequently varying diameter, the 

 tubes end at the apex of the pyramids of Malpighii, where they pour 

 their contained urine into the calyces. The urine then overflows into 

 the infundibula, and is finally drained from the pelvis by the ureter. 



We shall begin with a single typical tube; and, understanding its 

 histology, we can build up the organ, by simply multiplying this 

 element. 



A uriniferous tube, or tubule, commences in the cortex in a laby- 

 rinth (between the pyramids of Ferrein), as a thin-walled (g-sVo") sac 

 (riV')- This vesicle, with contents, is a Malpighian body; and its wall 

 is called the capsule of the same, or the capsule of Bowman. It is 

 made up of connective tissue and is the thickest part of the urinifer- 

 ous tube wall or membrana propria, the remaining portion being 

 thin and homogeneous. 



From one side of this, the expanded beginning of the tube, a 

 narrow neck ( T oVo- ") is projected, which immediately widens ( T J~o ") 

 into a tube the proximal convoluted. This tube (or this portion of 

 the tube) pursues a very tortuous course, always keeping between 

 Ferrein's pyramids, and finally approaches the base of a Malpighian 

 pyramid. Here it assumes an irregular spiral form the spiral tube 



Wo")- 



