312 



HISTOLOGY 



pouches known as the major and minor calyces. In the adult there are 

 usually two major calyces, one at either end of the pelvis, and from these 

 most of the minor calyces grow out; the others spring directly from the 

 main pelvic cavity. There are about eight in all. From the minor caly- 

 ces the collecting tubules grow out. Each tubule has an enlarged extremity 



FIG. 309. MODELS SHOWING SUCCESSIVE STAGES IN THE DEVELOPMENT OF A URINIFEBOUS TUBULE 



INCLUDING THE ASSOCIATED PORTION OF THE COLLECTING TUBULE. (Huber.) 



From a human embryo of the seventh month. X iCo. 



(Fig. 307) which divides into two branches with a U-shaped crotch, like 

 a tuning-fork. The branches subdivide repeatedly in the same manner, 

 so as to make pyramidal masses of straight tubules radiating from the 

 calyces. Thus the renal outgrowth from the Wolffian duct produces the 



