7 6 



PRACTICAL HISTOLOGY. 



are brown, and the protoplasm light brown. Such preparations are 

 well adapted for photographic reproductions. Some use a solution 

 in 70 per cent, alcohol. 



Vesuvin is much more soluble, and is used in the same way as 

 Bismarck brown. 



(F.) Other Aniline Dyes. 



Aniline Blue-Black. This has a remarkable power of staining 

 nerve-cells, as shown by Sankey. It is best adapted for staining 

 fresh nerve-tissues, although it is also used for staining in bulk. 

 It has little power of diffusing through them. (Lessons on Central 

 Nervous System.) 



TABLE showing some of the Aniline, Dyes in most Common Use, 

 arranged according to their Colour. 



E. Metallic Substances. 



1. Nitrate of Silver. This substance possesses the property of 

 forming a compound with intercellular substance, which darkens, 

 and becomes brown or black, on exposure to light. It is unequalled 

 for the study of the cement substance of epithelium and endo- 

 thelium, and for the cell-spaces of the cornea, and connective tissue 

 generally. The tissue, however, must be fresh the fresher the 

 better. Use a glass or horn rod to manipulate the tissue in the 

 fluid, not metallic instruments. 



Make a i per cent, solution, i.e., i gram of silver nitrate is 

 dissolved in 100 cc. of distilled water. This is kept as a stock. 

 A J or J per cent, solution is the strength usually employed. 



If it be desired to " silver " a part of the omentum or mesentery, 

 this membrane should be pinned out with hedgehog spines, without 

 being stretched, on a piece of flat cork with a large hole in it, so 

 that the solution can get to both sides of the membrane. A very 

 convenient plan is to pass the membrane over a porcelain or ebonite 

 ring, and fix it with another ring in the manner in which a skin is 

 fitted on a drum (figs. 45 and 46). 



Lave the membrane gently in distilled water to remove any 



