Bone 



GROUND SECTIONS 



83 



thickest sections of l)oiie are placed at tlie 

 outside of the piepaiatioii, or it will \)v im- 

 possible to avoid the slide's \vol)blinf; while 

 being ground. As soon as all the slabs of 

 bone have been placed, the balsam is 

 heated until it boils rapidly. The balsam 

 usually catches fire during this process, 

 but it may be extinguished by blowing on 

 it. A pair of forceps is finally used to push 

 each piece of bone into contact with the 

 glass and the sUde is cooled. 



The scratches from the earl)orundum 

 nuist now be polished out with pumice 

 powder. One secures either another piece 

 of glass or a flat hardwood board — they 

 are etiually good -and prepares on this a 

 paste of pumice and water exactly as the 

 carborundum paste was prepared. The 

 slide is washed to remove the carborun- 

 dum grains and then rubl)ed, with exactly 

 tiie same motion, in a slurry of pumice un- 

 til each section of bone is uniformly 



Fig. 31. Mounting bone slabs on glass slide. 



While the section is cooling, a pool of 

 water is poured on a slab of plate glass, 

 and carborundum powder, of about 100 

 mesh, is sprinkled in until a thick cream is 

 produced. The slide is then turned upside 

 down in this cream, as shown in Fig. 32, 

 and rubbed backward and forward with a 

 circular movement, so as to grind down 

 the bone. The grinding should be con- 

 tinued until the pieces of bone have been 

 reduced to a uniform thickness. It may be 

 necessary, from time to time, to add more 

 water, and the specimen should ))0 lifted 

 at intervals to make sure that the abrasive 

 fluid is underneath it, and not being 

 pushed out by a wall of balsam. 



smooth on the surface. Some people prefer 

 to use a hardwood, rather than a glass, 

 slab for the pumice. It is best to dry the 

 surface of the bone and to examine it un- 

 der a lens by strong reflected light to 

 make sure that the scratches have been 

 removed. 



The sections are now polished on a 

 horsehide strop cemented to a wood block. 

 The strop is lubricated with a thick cream 

 of either rouge or white rouge (eerie ox- 

 ide). The shde should be rubbed rapidly 

 with very little ])ressure; too much pres- 

 sure is liable to dry the sections. If dried 

 rouge is forced into the surface under 

 pressure it is almost impossible to remove 



