64 



formed too fast, accumulate in the tissues, inflate and distort them. 

 Many fixers contain acid (e. g., see 12, 14, 17, etc.), and in their 

 action give decalcification enough in the case of small calcified 

 objects. 



185. Directions for use. [10.] The tissue to be decalcified 

 had best be first thoroughly fixed and hardened by one of the approved 

 methods, and should be in 82% alcohol. In fixing, structures not 

 needed should be removed, muscles trimmed away from the bone, 

 etc. Bones or teeth should be opened with nippers or a saw, so that 

 the fluid may reach the marrow or pulp cavity. 



Place the hardened tissue in the decalcifier, where it should 

 remain until the lime salts have been entirely removed, as may be 

 ascertained by inserting a fine needle ; if any calcified matter remains 

 there will be a gritty feeling on using the needle. The time neces- 

 sary for complete decalcification will depend upon the size and den- 

 sity of the calcified tissue, and will vary from 3 to 15 days or longer. 

 The decalcifier should be changed after the first day, and if the tis- 

 sue is large it is best to change it subsequently two, three or more 

 times at intervals of several days. 



When decalcification is complete rinse the tissue well in water or 

 67% alcohol for a few minutes and place it in 67% alcohol for one or 

 two days and then in 82% alcohol for several days, or until ready to 

 imbed. The 82% alcohol should be changed once or twice in order 

 that the nitric acid may be well w r ashed out. Although paraffin in 

 many cases may be employed for imbedding, the celloidin method is 

 generally more satisfactory. 



Hematoxylin with eosin, hematoxylin with picro-fuchsin, and 

 hematoxylin with picro-carmine afford good stains; by staining 

 thoroughly with hematoxylin a differential staining of bone and 

 cartilage may be obtained. Mallory's connective tissue stain fre- 

 quently gives interesting pictures. 



(B). Sections of Dry Bone or Tooth. 



186. Though the general structure of bone and tooth is shown 

 moderately well when the tissue has been decalcified ( 184). the 

 Haversian canals, canaliculi and lacunae of bone and the dentinal 

 tubules of the teeth are shown much better in sections of dried, 

 non-decalcified, tissue rendered sufficiently thin for microscopic ex- 

 amination by grinding or filing. 



