198 EXCRETION BY THE KIDNEYS AND SKIN 



FIG. 58. A diagram of the sections of uriniferous tubes. 

 A, cortex limited externally by the capsule; a, subcapsular layer not containing 

 Malpighian corpuscles; a', inner stratum of cortex, also without Malpighian capsules; 

 B, boundary layer; C, medullary part next the boundary layer; i, Bowman's cap- 

 sule of Malpighian corpuscle; 2, neck of capsule; 3, first convoluted tubule; 4, spiral 

 tubule; 5, descending limb of Henle's loop; 6, the loop proper; 7, thick part of the 

 ascending limb; 8, spiral part of ascending limb; 9, narrow ascending limb in the 

 medullary ray; 10, the zigzag tubule; n, the second convoluted tubule; 12, the 

 functional tubule: 13, the collecting tubule of the medullary ray; 14, the collecting 

 tube of the boundary layer; 15, duct of Bellini. (Kirkes after Klein.) 



