216 PRACTICAL HISTOLOGY. 



Berlin blue, but the process requires considerable care 

 and experience, since it presents unusual difficulties. 

 Indeed, it is only quite recently that attempts to fill any 

 lymphatics except those in the deepest part of the mem- 

 brane have been successful. If a successful result is 

 obtained the injected portions are hardened in alcohol, 

 and vertical sections, which may be tolerably thick, made 

 and mounted in dammar. 



