326 CHAPTER XXV. 



its function in the mixtures given below is so to protect the 

 organic elements of tissues against the action of the mineral 

 acids that these can be used in a much more concentrated 

 form than would be otherwise advisable. 



HAUG advises the following procedure : Bring one grm. of 

 phloroglucin into 10 c.c. of pure, not fuming nitric acid (1*4 

 sp. gr.), and warm very slowly and carefully with gentle 

 agitation. There is formed a clear solution of (presumably) 

 a nitrate of phloroglucin. Dilute the solution with 100 c.c. 

 of distilled water, and add 10 c.c. of nitric acid. This gives 

 a solution containing 20 per cent, of acid, which is the proper 

 proportion. More water may be added to the solution, to 

 make it up to 300 c.c., if nitric acid be also added in the 

 proportion given. But the dilution must not be carried 

 beyond this point, in order that the preservative action of the 

 phloroglucin be not overmuch weakened. The process of 

 decalcification in this solution is extremely rapid, and there- 

 fore should be carefully watched. Foetal and young bones 

 become quite soft in half an hour ; small pieces of old and 

 hard bones (femur, temporal bone) in a few hours. Teeth 

 take longer, and may require, if time be an object, a solution 

 made with 35 to 45 per cent, of nitric acid. Wash out for two 

 days in running water. The tissues stain well. 



The solution may be made with hydrochloric acid instead 

 of nitric acid, ;iO per cent, of acid being taken, and 0*5 per 

 cent of sodium chloride added. 



For slow decalcification a 2 to 5 per cent, nitric acid solu- 

 tion may be used, or a mixture containing of phloroglucin 1 

 part, nitric acid 5, alcohol 70, and distilled water 30 parts. 



For the labyrinth, FERRERI advises a mixture containing 1 

 grm. of phloroglucin, dissolved with the aid of heat in 10 

 grms. of hydrochloric acid with 100 of water, 200 of 70 per 

 cent, alcohol being added after cooling. The mixture should 

 be changed once a week during thirty to forty days. 



Desilicifica tion . 



574. Hydrofluoric Acid (MAYEK, Zool. Anz., 1881, p. 593). 

 The objects are brought in alcohol into a glass vessel coated 

 internally with paraffin (otherwise the glass would be corroded 



