182 NORMAL HISTOLOGY. 



membrana propria lined throughout with a single 

 layer of epithelial cells, which differ greatly in char- 

 acter and form in different parts of the tubules ; the 

 tubules have received special names in different 

 parts of their course. 



Each tubule commences within a cortical pyramid, 

 in a dilatation called the glomerulus, with whose 

 capsule, presently to be described, its membrana 

 propria is continuous ; it is narrow as it leaves the 

 glomerulus, but broadens out at once into a wide, 

 convoluted canal convohited tubule which winds 

 about in the pyramid, finally approaching a medul- 

 lary ray ; this it enters, and, suddenly becoming very 

 narrow, descends more or less deeply into the 

 medulla ; here, widening somewhat, it turns sharply 

 on itself and ascends into a medullary ray again. 

 This portion of the tube, from the point at which 

 it becomes narrow and begins to descend in the 

 medullary ray, is called Henles loop, and the arms of 

 the loop are called, following the course which the 

 description has taken, the descending or narrow, and 

 the ascending or broad arms of Henle's loop. The 

 ascending arm of Henle's loop, on arriving in the 

 cortex, widens and enters a cortical pyramid, form- 

 ing what is known as the intercalated tubule ; this 

 resembles the convoluted tubules, among which it 

 winds in and out, and then passes over, entering a 

 medullary ray, into a straight uriniferous tubule. 

 This is again narrower than the convoluted tubules, 



