The Microscopical Preparations. 65 



Coarse approximative sections may be obtained with the saw 

 or dividing file (excepting silicified substances), but these instru- 

 ments are not applicable to longitudinal sections of small human 

 or other teeth, small bones, &c. Take now the object in the 

 fingers if sufficiently large, and grind it upon the coarse hone 

 with water, to which add " silex" if necessary, until the surface 

 coincides with the intended plane. Wash carefully : finish upon 

 the finer hone ; and polish upon soft linen stretched upon a 

 smooth block. 



If the object be too small to admit of immediate manipulation 

 it should be fastened upon a piece of glass with isinglass — or 

 what is better, upon thin paper well glued with the same sub- 

 stance upon glass; and a piece of thick paper or visiting card, 

 perforated with a free aperture for the object, must be attached 

 to the first paper. This is the guard, down to which the speci- 

 men must be ground with oil : and its thickness and the disposal 

 of the object require the exercise of good judgment. Hot water 

 will release everything; and chloroform remove the grease from 

 the specimen, which, like that ground with water, is ready for 

 the second part of the process. 



2d. Carefully cover the surface of a piece of the plate glass 

 with thin French letter paper ; next apply a paper guard, as be- 

 fore stated, but not thicker, for teeth and bone, thanji^th inch ; 

 then trace a few lines with a lead pencil upon the first paper in 

 . the little space, left in the guard so that the increasing transpar- 

 ency of a specimen being prepared may be appreciated ; and 

 finally moisten the " space" with isinglass to the extent of the 

 object, which must be delicately brushed over on the ground 

 surface and at the edges with tolerably thin isinglass before it is 

 cemented in its place. Gentle pressure should now be employed, 

 and maintained with a wire spring, or thread wound round about. 



In two or three hours the second side may be ground in oil ; 

 silex may be employed at first, or even a file ; but these means 

 must not be persevered in, and the operation must be completed 

 upon the bare hone. When the second side shall have been 

 wiped with chloroform it may be polished with a bit of silk 

 upon the finger ; and after spontaneous separation from the paper' 

 in hot water the specimen ought to be well washed on both 

 sides with a camel's hair pencil and soap water, dropped into 

 cold water, and thence extracted to dry. After immersion in 

 chloroform for a moment, and examination for the removal of 



