EXCRETORY AND REPRODUCTIVE SYSTEMS. 165 



no- 



The substance of the kidney is composed of an outer 

 cortical layer, about a half centimeter thick, and an inner 

 medullary substance adja- 

 cent to the pelvis, and pro- 

 jecting into the latter in the 

 form of a papilla. In the 

 cortical substance are hun- 

 dreds of Malpighian bodies, 

 each composed of a ball of 

 capillaries (Fig. 87) envel- 

 oped by the invaginated 

 enlarged extremity of a 

 tubule which carries away 

 the urine by a tortuous 

 course to the papilla (Fig. 

 88). In the Malpighian 

 bodies the water and other 

 mineral substances of the 

 urine are extracted from 

 the blood by means of the 

 epithelial cells forming the 

 inner wall of the capsule of 

 Bowman. These urinary 

 products pass through the 

 proximal convoluted tubule 

 and the loop of Henle to 

 the distal convoluted tubule, 

 where they are mingled 

 with the urea extracted from 

 the blood by the columnar 

 epithelial cells of the tubule. From this point the excretions 

 flow into the collecting tube which empties into the pelvis at 

 the papilla. In a prepared microscopic section of the kid- 

 ney, these Malpighian bodies and uriniferous tubules may be 

 seen with a microscope magnifying about 200 diameters. 



d 



FIG. 86. VENTRAL ASPECT OF FE- 

 MALE URINO-GENITAL SYSTEM 

 WITH THE BLADDER PULLED TO 

 ONE SIDE. 



a, Entrance of the urethra into the 

 vestibule; ao, aorta; bl, bladder; 

 cl, clitoris ; en, cornu or horn of 

 the uterus ; ft, Fallopian tube, the 

 left one is cut off; fm, fimbri- 

 ated extremity of the Fallopian 

 tube ; kd, kidney ; /, ovarian liga- 

 ment; ov, ovary; ra, renal ar- 

 tery ; rv, renal vein ; re, rectum ; 

 ur, ureter; ut, body of the 

 uterus ; uth, urethra ; 1)0, vena 

 cava; vg, vagina; vs, vestibule. 



