1895.J MICKOSCOriCAL JOURNAL. 2H:3 



Ammonia bichromate and osmic acid furnish the best re- 

 sults With a very keen razor cut a cube 1 



centim. in diameter, taking care not to compress it. From 

 this cube take a strip 1 mm. tliick, place it in 1 per cent 

 osmic acid. ; put the rest of the cube in ammonia bichro- 

 mate. 



The piece in the osmium solution should remain for 24 

 hours. Wash carefully, harden in gum and alcohol. 

 Section perpendicular to the surface of the organ, stain 

 in alum carmine, mount in glycerine. The piece in bi- 

 chromate should be left there for at least from 8 to 10 

 days. Wash, harden in gum and alcohol, stain in hgema- 

 toxylin and eosine, mount in balsam. Make two series 

 of sections, one parallel with the surface of the organ, 

 the other perpendicular. 



Epithelium of the Conviolnted Tubes. — If llxed by alco- 

 hol, by tlie bichromates or even by osmic acid, these pro- 

 duce alterations The striation of the cells is 



scarcely visible, the cell contracts and expells into the 

 tubule one or more sarcodic masses. The epithelium is 

 striated and hollowed by vacuoles, which give it the as- 

 pect of cup-shaped cells. The following rules are to be 

 followed for the examination of the striation in the kid- 

 ney of mammals. (1) Take the kidney from an animal 

 immediately after death. (2) With a very keen razor, 

 cut near the surface a slice 1 mm. or more on a side. 



(3) Fix by osmic acid vapor (2 hours), place in strong 

 alcohol (without washing) to complete the hardening. 



(4) Examine sections in water. 



The striated cells in the kidneys of the Batrachia hav- 

 ing more resistance than those of mammals, the preced- 

 ing technique will not be necessary to see the striae. Put 

 the kidney of the frog, or better that of the triton, in 

 absolute alcohol ; when hardened, section very thin so 

 that YOU may examine in the staining fluid. The striae 

 of the cells are very distinct. 



