Dry Wholemounts 



General Principles 



A dry wholemount consists essentially 

 of an object or objects enclosed within a 

 small, usually cylindrical, box attached to 

 the center of a microscope slide. The floor 

 of this box is almost invariably the surface 

 of the slide itself while the roof is formed 

 by the coversUp. The sides of the box are 

 produced by the attachment of a cell, 

 which may be a thin ring of cement, a 

 washerlike piece of paper or plastic, or a 

 squat cylinder of the same materials. The 

 object may be attached directly to the 

 glass surface of the sUde, if one desires to 

 make a transparent mount, or the surface 

 of the shde may be rendered opaque and 

 the object then attached to whatever sub- 

 stance is used to blacken the surface. 

 There are a number of decisions to be 

 made before preparing a dry wholemount. 

 The considerations governing these deci- 

 sions will be discussed in the order in 

 which they present themselves to the 

 technician. 



Selection of a Slide 



If the object is to be prepared as a trans- 

 parent wholemount one has no choice but 

 glass. None of the transparent plastics at 

 present available have a sufficiently hard 

 surface to be worth using. They are un- 

 breakable and easy to handle when first 

 made, but will become so scratched after 

 even a few months of use as to be worth- 

 less. The manufacturers of these slides 

 point out that they may be repohshed at 

 intervals, but there seems little point in 

 preferring them to glass which does not 

 become scratched. 



If the wholemount is to be prepared as 

 an opaque object, which is the case in 



probably 90% of all dry wholemounts, 

 there is little justification for using glass. 

 It has two great disadvantages: first, it^is 

 very easily broken; second, it is one of the 

 most difficult materials to which to cause 

 adhesives to stick. In the early days of 

 microscope mounting it was customary to 

 employ slides of well-seasoned mahogany 

 and, though this practice is today confined 

 to the mounters of Foraminifera, a brief 

 description of the preparation of these 

 shdes will be given. A piece of seasoned 

 mahogany, 3" by 1" in section, is secured 

 with the grain running parallel to the 

 three-inch face. This block is set up on end 

 in a vertical drill and a hole of the required 

 diameter drilled as deeply into it as is 

 possible with tools available. This hole 

 should be about Ke of an inch smaller 

 than the size of the coversUp which will be 

 used; that is, if ^^-inch coversUps are 

 customary an i He-inch drill is used to 

 make the hole. The actual size of the 

 covershps should be checked before drill- 

 ing, since many coverslips which are sold 

 as %-inch have a diameter of eighteen 

 millimeters, or a trifle less than '*%4. 

 When the hole has been drilled, the block 

 of wood is transferred to a circular saw 

 and slices about J^e of an inch in thickness 

 cut from it. These slices are, in effect, 

 3" XI" microscope shdes with a hole of 

 the required size in the center. A sheet of 

 strong, thin card is then cut into 3" X 1" 

 pieces, each of which is glued to the under 

 side of one of the shdes. The best way to 

 do this without warping the wooden strip 

 is to use shellac as an adhesive, either em- 

 ploying a very thick solution in alcohol 

 and permitting it to dry under pressure, or 



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