230 ELEMENTARY PHYSIOLOGY. [XXII. 



these are convoluted tubes and end-capsules 

 with their glomeruli arranged in double rows 

 between each two pyramids (the symmetrical 

 arrangement of the medullary rays and inter- 

 vening convoluted tubes may not be obvious 

 if the section is cut obliquely). In the outer 

 part of the cortex convoluted tubes only are 

 seen. 



3. Observe under a high power. 

 a. In the medulla 



a. The epithelium of the straight tubes 



(tubuli uriniferi recti); in the smaller 

 tubes, collecting tubes, this is composed 

 of short columnar or cubical cells with 

 spherical or ovoid nuclei ; in the larger 

 tubes, outflow tubes, it is composed of 

 longer columnar cells with ovoid nuclei ; 

 the lumina, distinct throughout, become 

 larger as the tubes increase in size. 



I. In the intermediate layer 



a. The continuation of the straight tubes 

 outwards in the medullary rays. 



{3. The loops of Henle, chiefly in the medul- 

 lary rays ; they run down also a variable 

 distance into the medulla. 



7. The ascending limbs of the loops; 

 these will probably be deeply stained, 

 they vary in size in different parts of 

 their course and are composed of cells 



