106 THE TISSUES 



TECHNIC 



(i) For the study of the minute structure of bone a section of undecalcified or 

 hard bone is required. Part of the shaft of one of the long bones is soaked for sev- 

 eral days in water and all the soft parts are removed. It is then placed in equal 

 parts alcohol and ether to remove all traces of fat and thoroughly dried (the 

 handle of a tooth or nail brush frequently furnishes good material and is already 

 dried). Thin longitudinal and transverse sections are now cut out with a bone 

 saw. One surface is next ground smooth, first on a glass plate, using emery and 

 water, then on a hone. The specimen is now fastened polished side down on a 

 block of wood or glass by means of sealing wax, and the other side polished 

 smooth in the same manner as the first, the bone being ground as thin as possible. 

 The sealing wax is removed by soaking in alcohol and the specimen looked at 

 with the low power. If not thin enough, it is gently rubbed on a fine hone. It 

 is then soaked in equal parts alcohol and ether, dried thoroughly, and mounted 

 in hard balsam. This is accomplished by placing a small bit of hard balsam on 

 a slide, melting, pushing a bit of the bone into the hot balsam, covering and 

 cooling as quickly as possible. The object of the hard balsam and quick cooling 

 is to prevent the balsam running into the lacunae and canaliculi and obscuring 

 them by its transparency. The air imprisoned in the lacuns and canaliculi 

 causes them to appear black when viewed by reflected light. 



(2) The structure of the bone cell is best studied in sections of decalcified 

 bone which has first been carefully fixed. (See technic i, p. 202.) 



