Chloride of Gold and Anilines. 43 



that it has some, is evident from the difference of the 

 action of anilin dyes on those specimens prepared in 

 gold, from those hardened in any other manner. 



A very good material for the purpose is the tail of a 

 young rat or mouse, placed in half per cent, solution of 

 gold chloride for an hour or two, and then decalcified 

 and hardened in the usual way. Very thin transverse 

 sections should be cut, and stained first in rosein and 

 then in iodine green. 



On examining the specimen the gold staining will he 

 seen on the periphery, bringing out the tendon cells, 

 and giving a dark hue to everything for a certain dis- 

 tance from the outside ; but within this a great variety 

 of colour will be found, the different tissues being 

 stained in a most gorgeous manner. In the middle 

 the bone trabeculse will be seen faintly stained, while 

 the calcified cartilage, in their centres, is stained a 

 bright colour, totally different. All these colours may 

 be varied by using different anilin solutions, and a very 

 pretty result may be obtained by simply staining with 

 iodine green. In the above instance the true bone is 

 only faintly stained, while the calcified cartilage takes 

 the colour deeply ; this may be reversed by using the 

 carmine and indigo -car mine process after the gold, when 

 the bone will be found deeply stained, while the calci- 

 fied cartilage is not stained at all, and looks like a clear 

 space in the bone trabeculas. These two processes will 

 be found invaluable in any investigation into the deve- 

 lopment of bone. 



