390 



STUDIES IN ADVANCED PHYSIOLOGY. 



at this point that almost all of the water of the secretion 

 finds its way unto the uriniferous tubnles. 



This dilatation connects with the regular tubular portion 

 of the duct. The portion immediately following the dilata- 

 tion is called the neck. Beyond the neck the tubule be- 

 comes somewhat convoluted, and is spoken of as the first 

 convoluted tubule. It then descends abruptly through the 

 cortex down into the medulla, this portion being called the 

 descending limb of Henle. In the medulla it makes a sharp 

 turn, called the loop of Henle and then ascends again 

 through medulla and cortex to almost the point of begin- 

 ning, this ascending portion being called the ascending 

 limb of Henle. It then usually bends and runs back almost 

 to its Malpighian corpuscle, this portion being called, be- 

 cause of its convoluted nature, the second convoluted 

 tubule. Near its Malpighian body it makes a sharp turn 

 again, flowing in an opposite direction, and on account of 



Fig. 130. DIAGRAM SHOWING THE COURSE OF TWO URINIFEROUS TUBULES. (After 

 Klein.) 



A, cortex; B, medulla; C, papilla; a, a', regions free from glomeruli. 

 For meaning of numbers see text. 



the somewhat angular turns is called the zig-zag tubule. 

 This zig-zag tubule soon leads into one of the large collect- 



