82 



THE ART OF MAKING MICROSCOPE SLIDES 



Bone 



The first thing is to secure a piece of dry 

 bone. The majority of museums have old 

 broken specimens from which they are 

 only too glad to give away a bone or two. 

 The example shown being sectioned in 

 Fig. 30 is part of the femur of a horse 

 which became accidentally broken. If no 

 dried specimen of bone is available, and 

 one is, therefore, forced to start with raw 

 material, it is fii'st necessary to boil the 

 bone for four or five hours in water in 

 order to remove as much of the protein 

 material from it as possible. If, moreover, 



handUng bone because it combines the 

 stiffness of a hacksaw with the thinness of 

 a jewelers' saw. The first cut is made at 

 right angles to the direction of the cut 

 shown and a second cut (as seen in the 

 illustration) is then made, parallel to the 

 free surface that has been cut, and at right 

 angles to the present position of the saw in 

 the figure. Several slabs are cut, as uni- 

 formly as possible, but the saw kerf is 

 stopped about a millimeter above the 

 horizontal cut, and a second cut made, 

 until (as is seen in the figure) as many 



Fig. 30. Sawing slabs of bone for sectioning. Note that the vertical kerfs have not been 



extended to meet the horizontal kerf. 



one is dealing with a long bone containing 

 marrow, it is necessary that it should be 

 cut with a hacksaw into short lengths in 

 order that the marrow may be removed by 

 boiUng. The bone is then taken from the 

 boiling water, dried for a day or two, and 

 then defatted by being soaked in any fat 

 solvent. About the cheapest and most 

 convenient solvent available is naphtha, 

 though if price is a secondary considera- 

 tion one can, of course, use xylene. Three 

 or four changes, each lasting a week, in a 

 considerable volume of solvent must be 

 made, and the bone should then be baked 

 in a low-temperature oven until the sol- 

 vent has been removed. 



A series of thin slabs is then cut, as 

 shown in Fig. 30. The saw there shown, 

 which is a cheap imitation of a hacksaw, is 

 the best that the author has found for 



slabs as are required have been outHned. 

 Each is then successively cut off. A con- 

 venient size slab for preparation of a 

 microscope shde is approximately }^i inch 

 square, which is the size shown in the 

 illustration. 



Single sections may be handled without 

 being attached to anything. Several blocks 

 may, however, be ground down at the 

 same time by cementing them to a slide 

 as shown in Fig. 31. The hot table (shown 

 in its entirety in Fig. 8) is heated to about 

 100°C. The slide is then hberally covered 

 with natural balsam — not a solution in 

 xylene — and the slabs laid in place. Each 

 block of bone will have a jagged corner 

 sticking from it, where it broke away just 

 before the saw cut was complete, and these 

 little jagged corners must be placed upper- 

 most. One must also be careful that the 



