187. Directions for procedure. Prepare thin transverse sec- 

 tions of dried bone in accordance with the directions below. Longi- 

 tudinal (radial) sections and tangential (surface) sections may also 

 be prepared in the same manner, the former to show the Haversian 

 canals and their anastomoses, the latter to indicate the shape of the 

 lacunae as seen in a different plane. 



1. Sawing the section. Make an exact transection of a part of 

 the shaft of a long bone. The section should be about 1 cm. long 

 and include the thickness of the shaft from the surface to the medul- 

 lary cavity. Make the sections about 1 mm. thick. 



2. Grinding the sections. Place the piece of bone on a cork or 

 piece of soft wood and wet it with water. File it on one side until 

 smooth and then turn it over. Continue the filing till the piece is 

 from .05 to .10 mm. thick, using the cover-glass measurer to deter- 

 mine the thickness. In the beginning one can press quite hard in 

 filing; as the section thins, more care should be exercised and the 

 pressure should lessen. 



A grinder, such as a fine carborundum wheel or emory wheel con- 

 nected with a variable speed electric motor is very useful and greatly 

 expedites the preparation of the sections. The carborundum wheel 

 should be horizontal and the sections ground on the flat surface of the 

 wheel, water being used to carry away the bone dust. 



3. Washing and drying the section. When the section is thin 

 enough, rinse it and dry it with lens paper. 



4. Mounting the sections in hard balsam. To prepare the bal- 

 sam, put two or three large drops on the middle of a slide and heat 

 the slide in some way to drive off the volatile constituents. Do not 

 heat the balsam hot enough to produce bubbles. When the balsam 

 chips after cooling, it is ready for use. 



In mounting, have the section and a clean cover so placed that 

 they may be easily and quickly grasped. A cork somewhat smaller 

 than the cover-glass should be within reach, and also a stone or 

 piece of glass upon which to quickly cool the specimen as soon as it 

 is mounted. 



Heat the slide until the balsam is well melted. Put the slide 

 upon a piece of paper, grasp the piece of bone with the forceps and 

 plunge it into the melted balsam; put on the cover as quickly as 

 possible and press it down with the cork; finally put the slide on 

 the stone or glass to cool the balsam quickly. All of this should be 



