1266 



PHYSIOLOGY 



free margin of these cells, where they abut on the lumen, is irregular. 

 This appearance is due to the readiness with which the cells undergo 

 alteration under the influence of different fixing reagents, especially 



FIG. 528. A portion of a convoluted tubule with ' rodtled ' epithelium. 



(HEIDENHAIN.) 



of such as contain water. When properly fixed it is seen that the 

 rodded structure as described by Heidenhain is due to rows of granules 

 arranged vertically to the basement membrane. Moreover the free 

 margin of the cells, instead of being irregular, consists of a well-marked 

 striated border, formed of a number of very fine hairs closely set 

 together and springing from a row of granules in the peripheral part 

 of the cell (Fig. 529). The hairs, which make up the striated border 



B 



V ~* 



t 



FIG. 529. Cross-sections of convoluted tubules from kidney of rat. (SATJER.) 

 A, during slight secretion ; B, during maximal secretion. 



(sometimes called the ' brush border '), have not been observed to 

 present ciliary movement, and are probably comparable with the 

 similar structures found clothing the free border of the epithelium of 

 the intestinal villus. Such cells are characteristic features of the 



