54 PRESERVING AND PREPARING PATHOLOGICAL SPECIMENS. 



Decalcifying. 



Bones which are the seat of lesions, and calcified tissues, must be 

 freed from lime salts before thin sections can be made. 



Tissues which are to be decalcified should be in small pieces and first 

 well hardened in alcohol or in Orth's fluid. 



Eapid decalcification may be secured by the combination with nitric 

 acid of phloroglucin, the latter agent preventing the swelling of the tissue 

 elements. One gram of phloroglucin is dissolved with gentle heat in 5 

 c.c. of nitric acid. This solution, when effervescence has ceased, is of a 

 ruby-red color. To this are added 70 c.c. of strong alcohol and 30 c.c. 

 of water. This solution deteriorates with age. Small pieces of bone or 

 other tissue are suspended by thread in relatively large quantities at 

 least twenty times the bulk of the specimens of this fluid. In from one 

 to twenty-four hours, depending upon the size of the piece of bone, 

 the decalcification is usually complete. The specimen is now washed 

 thoroughly in running water ; put for twenty-four hours in eighty-per- 

 cent alcohol and then in strong alcohol. Bone decalcified in this way 

 may be stained with haematoxylin and eosin. 



Embedding and Section Cutting. 



EMBEDDING. 



Some dense tissues, after being well hardened, are sufficiently solid to 

 permit of thin sections being made from them without further prepara- 

 tion, but in most cases very thin sections cannot be prepared without fill- 

 ing the interstices of the tissue with some embedding material, which 

 gives it greater consistence and holds the tissue elements firmly in their 

 natural relations to one another, while the section is being made. Cel- 

 loidin and paraffin are the most generally useful materials for this 

 purpose. 



CELLOIDIN, a non-explosive, purified form of gun-cotton, is best ob- 

 tained in the form of thin shavings, since in this form it is most easily 

 dissolved. A six -per- cent solution is made in equal part of sulphuric 

 ether and strong alcohol. The specimen in small pieces is soaked for 

 twelve hours in this celloidiu solution, diluted with an equal amount of 

 the mixture of alcohol and ether, then for twelve hours in the six-per- 

 cent celloidin solution. If the specimen be small and require but little 

 support, it may now be laid directly on the end of a small block of wood 

 or cube of glass or vulcanite, and a few drops of celloidiu poured around 

 it. In most cases, however, it is better to make a small paper box, in 

 which the specimen is placed in a proper position, and the celloidin 

 poured in around it so as completely to enclose it. In either case a con- 

 siderable quantity of celloidin should be poured around the specimen, 

 since the celloidin shrinks considerably in hardening. The paper box 

 may be made by winding a strip of thin paper around the end of the 



