THE CONNECTIVE SUBSTANCE GROUP. 93 



be treated precisely as any other tissue of the body. If more 

 time is at the disposal of the student, chromic acid may be 

 used in a J per cent, solution. This process is rather slow, re- 

 quiring several months. It may be materially hastened by the 

 use of nitric acid (2 per cent.). It has been found that after 

 immersion in chromic acid for a few days, the soft parts are 

 rendered insensible to the action of other strong acids, such as 

 nitric and hydrochloric, when used in the dilute form. These 

 chromic acid preparations are exceedingly beautiful objects 



FIG. 37. Bone lacunaa with their processes. (Rollett. ) 



when seen with low powers. The matrix is of a deep grass 

 green. If a thin section is stained with borax-carmine (Arnold's 

 formula) the bone-corpuscles and connective tissue are stained 

 red, and the contrast of color brings out the finer elements 

 very distinctly. 



Picro-carmine may also be used, and then the muscular tis- 

 sue, if any chance to adhere to the bone, is stained yellow ; or 

 eosine and hsematoxylin may be used instead of borax car- 

 mine, and thus very excellent examples of triple staining pro- 

 cured. Sometimes a saturated solution of picric acid is em- 

 ployed to decalcify, but the excess of acid, after taking out 

 the bone-earths should be thoroughly removed by soaking in 



