94 THE KIDNEYS, BY C. LTJDWIG. 



which in proceeding from the medulla towards the cortex are 

 arranged in an imbricated manner. 



In the windings of the intermediary portion the epithelial 

 lining reassumes the pulpy character it presented in the 



Fig. 147. 



Fig. 147. From an ascending limb of a loop of Henle, to show the 

 imbricated arrangement of the epithelium. 



tortuous portion of the tubule. In the collecting tubes, as far 

 as the ductus papillares, the epithelium is composed of isolated 

 and distinctly defined columnar cells, the broader base of which 

 is applied to the wall of the canal, and their truncated apices 

 towards its lumen. Finally, in the ductus papillares the 



Fig. 148. 



Fig. 148. Transverse section through the fresh medullary portion 

 of a kidney, to show the characters of the epithelium in the tubuli 

 uriniferi. The dark circles (6) are sections of bloodvessels. The epi- 

 thelium is quite transparent, so that the spheroidal form of the nuclei 

 is clearly visible. R, Collecting tubes, in which the epithelial cells 

 are completely individualised ; s, slender and wide limbs of the 

 loop. Between the tubules is a mass of striated connective tissue. 



tubules lose their basement membrane, so that the wall is 

 here formed of the epithelium alone, just as occurs in the ducts 

 of the sweat glands where they perforate the epidermis. 



