90 PRACTICAL HISTOLOGY [XI 



Fat marrow may be obtained by splitting a long bone, it may 

 be fixed in mercuric chloride, formaline, or in any of the usual 

 reagents ; or a short piece of bone may be put in the fixing 

 agent for a day or more and the medulla then pushed out with 

 a rod. 



Fixing and decalcifying bone and teeth. Tissues containing 

 lime salts may be treated with a hardening agent before 

 decalcification ; or treated with a reagent which fixes and 

 decalcifies at the same time. As soon as decalcification is 

 complete the tissue should be washed in running water for 

 one to two days ; as a rule it is best not to cut at once but to 

 pass through alcohols, and keep in 75 p.c. to 95 p.c. alcohol for 

 some days. 



Fixing. Any fixing agent may be used ; if the piece of bone 

 is not too large, those which penetrate best such as alcohol are 

 most generally applicable. 



Decalcifying after fixation. The tissue is placed in 

 (a] 1 to 2 p.c. nitric acid. 



(6) 75 p.c. alcohol containing 1 to 2 p.c. nitric acid. 

 The process may be quickened, if necessary, by using stronger 

 acid up to 5 p.c. 



(c) Strong nitric acid with phloroglucin. This is used where 

 rapid decalcification is required ; add 1 gram of phloroglucin to 

 10 c.c. of nitric acid 1'4 sp. gr., warm slowly and carefully, stirring 

 the while ; a rather violent solution of the phloroglucin will take 

 place, forming a dark red fluid. To this add 100 c.c. water and 

 10 c.c. nitric acid. (Haug.) Fostal and young bones are decal- 

 cified in about half-an-hour ; small pieces of hard adult bones in 

 some hours : large pieces of hard bone and teeth take a day or 

 more. 



Simultaneous fixation and decalcification. The decalcification 

 in this case is slow (one to several months). The fluid should 

 be shaken gently every day, and renewed at intervals of a few 

 days. 



Picric acid in saturated aqueous solution gives excellent 



