206 



UROGENITAL SYSTEM 



capsule, the two constituting a renal corpuscle of the mesonephros (Fig. 199 D). 

 In the human embryo, the tubules do not branch or coil as in pig embryos, con- 

 sequently the mesonephros is relatively smaller. At 10 mm. 32 to 34 tubules are 

 present in each mesonephros and the glomeruli are conspicuous (Fig. 200). 

 Each tubule shows a distal excretory and a proximal collecting portion which 

 connects with the duct (Fig. 201). 



The glomeruli form a single median column, the tubules are dorsal and the 



Mesdnt/Jift'c duct 



Anlouge of 

 mesonephric tubule. 



Degenerating r\ I 



mesonep/ir/'c corpatcltJJ^ 



jeneiratwg mescnt^ 

 Co/puscteJ tuhuLes 



Tuhule 



Bowman-s- capsule 



Fig. 199. — Diagrams showing the differentia- 

 tion of the mesonephric tubules (modified after Felix) . 

 L, lateral; M, median. 



Mesonephric 

 duct 



■ Treter ^'""r*"" 



Fig. 200. — Diagram showing the anlages 

 of the urinary organs from the left side (based 

 on reconstructions by Keibel and Felix). 



duct is lateral in position. Ventro-lateral branches from the aorta supply the 

 glomeruli, while the posterior cardinal veins, dorsal in position, break up into a 

 network of sinusoids about the tubules (see Chapter IX) . 



The primary excretory duct or mesonephric duct is solid in 4.25 mm. em- 

 bryos. A lumen is formed at 7 mm. wider opposite the openings of the tubules. 

 The duct is important as from it grows out the ureteric anlage of the permanent 

 kidney, while the duct itself is transformed into the genital duct of the male, and 



